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"@  = y  W M  h [ M J ED e  w i w s *  Q K ĺ <  Ǹ 4 ̽ n " n Ю ѣ H v  ( | PAGET N+        5   q   $`  A  "  q H!# p  }    # `Pi* + ,g - . SGq?I n@@@ u 3 4 5I 6 74 8! 9 :H ; FC H I H!#J K= L @R0S90TD0U0Z0[0]00(B`_0b< d fa 0v 1 k| g mx n o r  0@_Hs  8E^Ht NrCjXx y# z ~ @ @ o ! ?q   t g @BKGDWBMAPW0 @ CARDtu8 8? Statement on EvolutionRt? Back to Texton mouseUp go to card 11 end mouseUpx p? Main Menuon mouseUp set scroll of card field 1 of card 11 to 0 go to Card 2 end mouseUpv ? Submenuon mouseUp set scroll of card field 1 of card 11 to 0 go to Card 5 end mouseUp"dt  TIME@7BMAPuG^CARD $2tRo? Introductionon mouseUp go to Card 89 end mouseUpZ fA? The Scientific Methodon mouseUp go to Card 4 end mouseUpX~@d? Comparative Anatomyon mouseUp go to card 70 end mouseUpZ~A? Historical Backgroundon mouseUp go to Card 5 end mouseUp\@d? The Geological Recordon mouseUp go to card 115 end mouseUpjA? The Genetic Structure of Populationson mouseUp go to card 18 end mouseUpV@d? Human Evolutionon mouseUp go to card 168 end mouseUp`A? Probability and Statisticson mouseUp go to card 38 end mouseUpXA? Natural Selectionon mouseUp go to card 198 end mouseUp`f@d? The Processes of Speciationon mouseUp go to card 40 end mouseUpT|? Quiton mouseUp doMenu "Quit Hypercard" end mouseUp\@d? Evolution of Behavioron mouseUp go to card 181 end mouseUpV @C? In the Laboratoryon mouseUp go to card 3 end mouseUp"oL v B@Р? Self Test on mouseUp show card field 3 wait 3 seconds hide card field 3 end mouseUp"_] r }? Index on mouseUp show card field 4 wait 3 seconds hide card field 4 end mouseUp"!d+ *"<?Main Menu"#e  Not yet done!This section is not done yet.Not done yetNot done yetCARD "XN p? Main Menuon mouseUp go to Card 2 end mouseUp\G? Chromosome Phylogenieson mouseUp go to card 45 end mouseUp"w@ R>H? Morphoclineson mouseUp go to card 44 end mouseUpXH? Routine Procedureson mouseUp go to card 41 end mouseUpZH? Blending Inheritanceon mouseUp go to card 42 end mouseUpXH? Study of variationon mouseUp go to card 43 end mouseUpRG? Random Drifton mouseUp go to card 46 end mouseUpN G? Beaneticson mouseUp go to card 47 end mouseUp^!G>? Trends in Human Evolutionon mouseUp go to card 48 end mouseUp2" ??In the Laboratory Not yet done @CARDNnl? Main Menuon mouseUp set scroll of card field 1 to 0 go to Card 2 end mouseUp6 8? Historical Backgroundl ? Submenuon mouseUp set scroll of card field 1 to 0 go to Card 5 end mouseUp89x? Statement on Evolution"Jb Lw? Diagramon mouseUp go to Card 92 end mouseUpI' n u STATEMENT ON EVOLUTION The best way to sum up the basic tenets of biological evolution is from the chapter headings of Darwin's book On the Origin of Species. Chapter 1. Variation under domestication. Chapter 2. Variation under nature. Chapter 3. Struggle for existence. Chapter 4. Natural selection or the survival of the fittest. Chapter 5. Laws of variation. Chapter 6. Difficulties of the theory. Chapter 7. Miscellaneous objections to the theory of natural selection. Chapter 8. Instinct. Chapter 9. Hybridism. Chapter 10. On the imperfection of the geological record. Chapter 11. On the geological succession of organic beings. Chapter 12. Geographical distribution. Chapter 13. Geographical distribution, continued Chapter 14. Mutual affinities of organic beings; morphology; embryology; rudimentary organs. Chapter15. Recapitulation and conclusion. Chapters 1-4 of the Origin sum up the basic ideas on the evolution of species by means of natural selection. Chapters 5-9 consider some problematic issues not well understood at Darwins time. In chapters 10-14, Darwin considers some clues about evolution provided by the geological record, the geographical distribution of the many forms of living things, and by comparative anatomy. Most of the difficulties, mentioned in the Origin, center around the sources of variation. The contemporaries of Darwin, believed in blending inheritance, and it does not take much insight to see that blending inheritance would erode variation. Darwin observed a tremendously rich variation of living things everywhere he went. Where did this variation come from? This was a tantalizing question for him. As it happened, Mendel whose monograph, Experiments in Plant Hybridization, was in Darwins private library, provided the answer. It is ironic that Darwin never made the connection. Today we know that one of the sources of variation is genetic in the form of mutations and recombination, another source is environmental, and yet another is from some random processes. The random processes are all associated either with sampling error, as in the case of the founder's principle, where small sample size between generations results in genetic drift, or it is associated with the fate of selectively neutral traits, that is traits not under the influence of natural selection. It has been found, however, that often traits that were thought to be selectively neutral are still selected for through pleiotropy. This finding does not exclude the possibility of selectively neutral traits, but it points out the need for thorough investigation of such traits. In the Origin, the matter of survival of the fittest was presented in terms of a yes or no situation. Today we have toned down this either live or die harshness of the selection process. A better expression, that we use today, is the differential survival of variants, implying that survival is a matter of degrees expressed in terms of the number of offspring, and not as an either-or phenomenon. Another important feature of this survival process is that it implies the passage from one generation to the next. Each new generation is a somewhat biased sample of the previous one; biased by selection of the variants relative to a constantly changing environment. The result is that the composition of each new generation is adapted to the changing circumstances and becomes somewhat different from the composition of the previous generation. These are the observations, which lead us to a better understanding of the evolution of species. Of course, the evolution process considered here is that of microevolution, that is the accumulation of changes in small increments through long periods of time. Given enough time, however, even major changes can be accomplished through microevolution. End of section.FREEFree Object olution process implied here is that of microevolution which means the accumulation of changes in small increments through time. In this way, given enough time, even major changes can accomplished. Click on the Diagram button below to see the visual presentation of the basic state- ments of the Origin. End of section. CARD+_ lx ? Submenuon mouseUp Set scroll of card field 1 of card 29 to 0 go to Card 20 end mouseUpx p? Main Menuon mouseUp Set scroll of card field 1 of card 29 to 0 go to Card 2 end mouseUp4 8? Concealed Variation"Jn N|? Figure 1on mouseUp go to card 243 end mouseUpN{ߠ? Figure 2on mouseUp go to card 244 end mouseUp g:;- 2l  CONCEALED VARIATION. It has been found that a great deal of genetic variation effecting fitness remains hidden in heterozygous condition in a profusion of multiple allelic and polygenic systems. There are some rather ingenious methods to assess the amount of such concealed variation. One of these is the "balancer" method described below. The principle of the "balancer" method is to render an autosomal wild type chromosome homozygous with itself and to see how this effects viability. The idea is that there may be a number of recessive genes along wild type chromosomes with some effect on viability and fitness, but being in heterozygous condition, they remain hidden. Rendering them homozygous, they will show up in the phenotype and can be assessed as to their effect, which is then estimated from a comparison between observed and expected ratios of spe- cific phenotypes. These studies have been originally made by Dobzhansky and Spassky (1963) for the second chromosome in Drosophila pseudoobscura. The "balancer" stock consists of flies in which one of the second chromosomes has a re- cessive and a dominant marker, protected from recombination by a large inversion. The dominant marker is lethal when homozygous. The other second chromosome has the same recessive marker as the first, but in place of the dominant marker it has a recessive lethal gene. The second pair of chromosomes in the "balancer" stock looks like this: r D r l It is easy to see that the stock will maintain itself since neither rD//rD nor rl//rl are viable. Using the "balancer" stock, there are three crosses to be made. In the first cross, wild second chromosomes are brought into the "balancer" stock. The second cross selects one individual second chromosome and makes a number of copies of it. In the third cross the wild second chromosome is rendered homozygous with itself and its viability is assessed. It is a good idea to run a second set of three crosses parallel with the first set. This will allow us to assess the viability of another second chromosome, but also it will make it possible to compare the two selected chromosomes in both, homozygous and heterozygous conditions. It is better to measure the viability of a homozygous wild type chromosome against a heterozygous wild type situation than against the "balancer" genotype, even if that comparison is somewhat indirect. Figure 1 below will take you to the card showing the three crosses in a more visual manner. Figure 2 shows how to set up a control cross for comparison. End of Section.yP@ FREEFree Object r to the Weber- Fechner law: effectiveness of model varied inversely with the square of distance between model and male. In conclusion, the male Grayling butterfly did not recognize the female from a gestalt as we would have done. For the male the female was a dark object, close to black, could be of any shape, but had to appear at a close range and had to fly in a wavy fashion. Click on the "Graphs" button below to see a visual summary of the results of Tinbergen's experiments. End of section.CARD$ tP@? Introductionon mouseUp go to card 6 end mouseUpV@? Static World Viewon mouseUp go to card 7 end mouseUpV2@? Dynamic World Viewon mouseUp go to card 8 end mouseUpL?? Voyageon mouseUp go to card 228 end mouseUp\?? Statement on Evolutionon mouseUp go to card 11 end mouseUp6 8? Historical BackgroundL ?2? Esssayson mouseUp go to card 12 end mouseUpN l? Main Menuon mouseUp go to Card 2 end mouseUp @CARDaU @n p? Main Menuon mouseUp set scroll of card field 1 to 0 go to Card 2 end mouseUp0 8? Special Studiesn ? Sub Menuon mouseUp set scroll of card field 1 to 0 go to Card 73 end mouseUp29v? Vertebrate HeartsLu? Diagramon mouseUp go to card 97 end mouseUp"C r  ;A  SPECIAL STUDIES: VERTEBRATE HEARTS. Comparing the hearts of vertebrates, a morphocline can be constructed with polarity from fish through amphibians and reptiles, to mammals. The trend in the morphocline seems to re- flect evolutionary changes leading to a progressive separation of the systemic and pulmonary circulations as the earlier vertebrates invaded the land and breathing through gills was changed to breathing through lungs. It should be noted that in the transitionary forms, as in amphibians, breathing through the skin had a special importance. The direction of blood flow is forwards in the ventral aorta and backwards in the dorsal aorta. From the tissues and organs, the blood is collected through veins and led back to the heart in ventral vessels. In fishes there is a single atrium and a single ventricle. The sinus venosus and the con- tractile conus arteriosus are large. The blood in the heart is low in oxygen but it is sent to the gills through the ventral aorta and becomes enriched by oxygen by the time it reaches the dorsal aorta. In amphibians, the atrium is separated into left and right chambers. The function of the lungs is not efficient because the oxygenated blood from the lungs reaches the heart's left atrium but then it becomes mixed in the single ventricle with blood from the veins that is low in oxygen.. The oxygen need of the tissues is supplemented by respiration through the skin. Both, the conus arteriosus and the venus sinus are fairly large. In reptiles there is a complete separation of the right and left atria and a nearly complete separation of the two ventricles. The position of the systemic arteries is such that most of the oxygenated blood from the pulmonary vein and the left side of the heart reaches these arteries while the blood from the major veins and the right side of the heart reaches mostly the pulmonary artery. There is no more conus arteriosus and the venous sinus is much reduced. In mammals, the separation of the left and the right sides of the heart is complete and so the systemic and pulmonary circulations are distinct. Both, the conus arterious and the venous sinus are absent. Blood from the lungs reaches the left side of the heart and leaves it through the systemic artery. which goes to the tissues and organs. Blood from the veins goes into the right side of the heart and leaves it through the pulmonary artery which goes to the lungs. Click on the Diagram button below to see the various arrangements. End of section. @FREEFree Object f introduction.?CARDb =nl? Main Menuon mouseUp set scroll of card field 1 to 0 go to Card 2 end mouseUp6 8? Historical Backgroundl ? Submenuon mouseUp set scroll of card field 1 to 0 go to Card 5 end mouseUp29x? Static World View"Jb Nt? Pictureson mouseUp go to Card 226 end mouseUp=.'&&$.<.N66=l=m=n THE STATIC WORLDVIEW. The static worldview, still prevalent in the 19th century, comes from a number of different sources. These sources are the ancient Biblical, the Greek Philosophical, the Scholastic Medieval, and the Renaissance Classical. The following is a presentation of the prevalent concepts from each source with a brief interpretation. THE ANCIENT BIBLICAL SOURCES. A. The first account of creation: Genesis 1:1-31 and 2:1-3. In the beginning God created the heavens and the earth. Now the earth was formless and empty, darkness was over the surface of the deep, and the Spirit of God was hovering over the waters. And God said, "Let there be light," and there was light. God saw that the light was good, and he separated the light from the darkness. God called the light "day," and the darkness he called "night." And there was evening, and there was morning --the first day. And God said, "Let there be an expanse between the waters to separate water from water." So God made the expanse and separated the water under the expanse from the water above it. And it was so. God called the expanse "sky." And there was evening, and there was morning --the second day. And God said, "Let the water under the sky be gathered to one place, and let dry ground appear." And it was so. God called the dry ground "land," and the gathered waters he called "seas." And God saw that it was good. Then God said, "Let the land produce vegetation: seed-bearing plants and trees on the land that bear fruit with seed in it, according to their various kinds." And it was so. The land produced vegetation: plants bearing seed according to their kinds and trees bearing fruit with seed in it according to their kinds. And God saw that it was good. And there was evening, and there was morning --the third day. And God said, "Let there be lights in the expanse of the sky to separate the day from the night, and let them serve as signs to mark seasons and days and years, and let them be lights in the expanse of the sky to give light on the earth." And it was so. God made two great lights --the greater light to govern the day and the lesser light to govern the night. He also made the stars. God set them in the expanse of the sky to give light on the earth, to govern the day and the night, and to separate light from darkness. And God saw that it was good. And there was evening, and there was morning --the fourth day. And God said, "Let the water teem with living creatures, and let birds fly above the earth across the expanse of the sky." So God created the great creatures of the sea and every living and moving thing with which the water teems, according to their kinds, and every winged bird according to its kind. And God saw that it was good. God blessed them and said, "Be fruitful and increase in number and fill the water in the seas, and let the birds increase on the earth." And there was evening, and there was morning --the fifth day. And God said, "Let the land produce living creatures according to their kinds: livestock, creatures that move along the ground, and wild animals, each according to its kind." And it was so. God made the wild animals according to their kinds, the livestock according to their kinds, and all the creatures that move along the ground according to their kinds. And God saw that it was good. Then God said, "Let us make man in our image, in our likeness, and let them rule over the fish of the sea and the birds of the air, over the livestock, over all the earth, and over all the creatures that move along the ground." So God created man in his own image, in the image of God he created him; male and female he created them. God blessed them and said to them, "Be fruitful and increase in number; fill the earth and subdue it. Rule over the fish of the sea and the birds of the air and over every living creature that moves on the ground." Then God said, "I give you every seed-bearing plant on the face of the whole earth and every tree that has fruit with seed in it. They will be yours for food. And to all the beasts of the earth and all the birds of the air and all the creatures that move on the ground, everything that has the breath of life in it, I give every green plant for food." And it was so. God saw all that he had made, and it was very good. And there was evening, and there was morning --the sixth day. Thus the heavens and the earth were completed in all their vast array. By the seventh day God had finished the work he had been doing; so on the seventh day he rested from all his work. And God blessed the seventh day and made it holy, because on it he rested from all the work of creating that he had done. (Genesis 1:1-31, 2:1-3) The event of creation is being described in the book of Genesis in anthropomorphic terms as an event that took place in time, given here as six days, and has been completed within that same period of time. By the end of all the creating, God was tired and rested on the seventh day. The anthropomorphic images and expressions need to be properly interpreted today. This anthropomorphism represents the cultural wrappings of a theological, trans cultural statement about God who is the Creator of everything. Part of the cultural feature of the presentation is the idea that creation is an accomplished fact and not an ongoing process. Putting creation into time and then into the past opens an easy way to a static interpretation of the world. Of course, the book of Genesis is not a bio- logical but a theological writing. Nonetheless, according to a static cosmology, and without resolving the anthropomorphic slant, it is easy to construe some ideas about the immutability of species from the first two chapters of the book of Genesis. Such biological concepts, however, would have been totally alien in the 5th century BC when this book was written. They more belong to the cultural slant of the nineteenth century. (See the essay on "Solution of the Controversy." B. The beginning of the book of Ecclesiastes presents a world without change: The words of the Teacher, son of David, king in Jerusalem: "Meaningless! Meaningless!" says the Teacher. "Utterly meaningless! Everything is meaningless." What does man gain from all his labor at which he toils under the sun? Generations come and generations go, but the earth remains forever. The sun rises and the sun sets, and hurries back to where it rises. The wind blows to the south and turns to the north; round and round it goes, ever returning on its course. All streams flow into the sea, yet the sea is never full. To the place the streams come from, there they return again. All things are wearisome, more than one can say. The eye never has enough of seeing, nor the ear its fill of hearing. What has been will be again, what has been done will be done again; there is nothing new under the sun. Is there anything of which one can say, "Look! This is something new"? It was here already, long ago; it was here before our time. There is no remembrance of men of old, and even those who are yet to come will not be remembered by those who follow. (Eccl. 1:1-11) Some to King Solomon, the son and successor of King David, has attributed this quoted passage from the book of Ecclesiastes. King Solomon reigned from about 972 BC until his death in 922. The Book of Ecclesiastes is part of the wisdom literature of the Old Testament writings together with such books as the Psalms, the Proverbs, the book of Job, and the Song of Songs. Since its contents reflect a great deal of thoughts and sentiments of the Egyptian Hellenistic period influenced by Stoic, Epicurean, and Cynic philosophies, it probably dates back to the third century BC. What is important about this quote is its worldview of meaningless stagnation in the complete absence of anything new. This quote is a tiny fragment of a vast literature about a fundamentally static world. Being part of the Bible for both Jews and Christians, the book is of great influence. THE GREEK PHILOSOPHICAL SOURCES. A. Plato. Plato was born in Athens in c. 428 BC. His parents were of distinguished Athenian families much involved in the cultural life of Periclean Athens. The young Plato, a pupil of Socrates, who was also a good friend of his family, was destined for an aristocratic political career. The excesses of Athenian political life, and then the execution of Socrates (399) had profound effect on his life and lead him to give up his political ambitions. in the year around 388 he founded the Academy, an institution devoted to research and instruction in philosophy and the sciences. Plato died in the year 348 or 347 BC. Much of Plato's writings are in the form of some 26 dialogues. He is deeply involved with such questions as "What is temperance, courage, holiness, and justice?" To answer such questions, Plato developed his theory of Forms. According to this theory, the Forms constitute a realm of an unchanging being to which the world of individual changing objects is subordinate. Central to Plato's thought is the power of reason to reveal the intelligibility and order governing the changing world of appearance. The relationship of these two worlds to one another, the world of being and the world of appearance, was deeply problematic to Plato. Plato gave the best presentation of this problem in the book, Republic, by the Divided Line and the Image of the Cave, which describe the hierarchical picture of Reality, all guided by the highest of all Forms. Plato called this top level Form the Good, which shines upon the whole structure of reality as the sun shines upon the visible objects. Plato was among the most significant thinkers of the ancient world. His work set forth most of the important problems and concepts of Western philosophy and his influence has remained profound from ancient to modern times. Alfred North Whitehead wrote, "The safest general characterization of the whole Western philosophical tradition is that it consists of a series of footnotes to Plato." B. Aristotle. Equally important as a source of influence upon Western thought was Aristotle (384-322), Plato's student. Aristotle was born in Stagira in northern Greece. His father, Nichomachus, was a well-established physician. Aristotle's aim was to organize human knowledge on a firm theoretical basis and to expand it in all directions. Although he did not accept Plato's theory of the Forms, and, being a keen observer, he attributed importance to the objects of the sensory world, yet he remained in his ideas about science in a deductive system based on self-evident axioms. He considered changes in terms of leading something from what it has been potentially to what it now became actually. Changes are carried out in the static interplay of matter and form without involving the essence of things. Most impressive was his system of logic, which is still very much in use today. C. Ptolemy. Ptolemy was one of the Greek astronomers and geographers of the second century AD. He propounded the geocentric world system which then successfully prevailed for the next fourteen centuries. He made most of his astronomical observations from Alexandria, Egypt, during the period of AD 127-41. Ptolemy's major work on astronomy was the Almagest in which he provided mathematical theories about the motions of the Sun, the Moon, and the planets. Ptolemy's geometric models employed combinations of circles and epicycles in the framework of the basic earth centered system already described by Aristotle. Ptolemy's views were tremendously influential. His geocentric world system was not superseded until Copernicus presented his heliocentric theory in the De revolutionibus of 1543. THE SCOLASTIC MEDIEVAL SOURCES. Both, Platonic and Aristotelian traditions have been carried through the centuries of the Middle Ages under the protection of Christian scholastic philosophy. At various times, one or the other was in favor. After the closing of the Academy, Neoplatonism continued to flourish in the Islamic and Byzantine world, and Latin Neoplatonism was a strong intellectual factor throughout the Middle Ages. It was the Byzantine philosopher Pletho who introduced the study of Plato to Renaissance Florence in the 14th century. Platonism reached England soon after and survived there well into the 19th and 20th centuries through the group known as the Cambridge Platonists. It was through the work of St. Thomas Aquinas, a Dominican theologian of the 13th century that the work of Aristotle was brought into Christianity and into the time of the Renaissance revival of classical philosophies and art of the Western world. St. Thomas's thought embodied the conviction that Christian revelation and human knowledge are facets of a single truth and cannot be in conflict with one another. This allowed him to achieve a remarkable synthesis of secular and theological issues. Without denying the importance of sense perception, the ultimate sources of knowledge for Thomas were the self-evident principles. As to faith the source of knowledge was based primarily on authority of God brought to us through revelation, which, however, contains nothing that would be against reason. Of course, the worldview of Thomas remained essentially the same as the classical static cosmologies of the ancient Greek philosophers. THE CLASSICAL RENAISSANCE SOURCES. With the revival of Classics through the Renaissance, a period of European history from the fourteenth to the late sixteenth centuries, much of the philosophy and cosmology of the ancient Greeks were brought into Western Civilization. Many of the important centers of learning in Europe, as exemplified by the University of Oxford in England, became deeply entrenched in the classical traditions bringing those well into our own times. Charles Curran in a book on Contemporary Problems in Moral Theology (1970) captures well the taste of the classical static cosmology prevalent up to most recent times. "The classicist worldview emphasizes the static, the immutable, the eternal, and the unchanging. The Greek column symbolizes this very well. There is no movement or dynamism about a Doric or Ionic column; the simple Greek column avoids all frills and baroque trimmings. The stately Greek column gives the impression of solidity, eternity, and immutability. Its majestic and sober lines emphasize an order and harmony which appear to last forever. This classical worldview speaks in terms of substances and essences. Time and history are 'accidents' which do not really change the constitution of reality itself. Essences remain unchangeable and can only go through accidental changes in the course of time. Growth, dynamism, and progress therefore receive little attention." "The Platonic world of ideas well illustrates this classical worldview. Everything is essentially spelled out from all eternity, for the immutable essences, the universals, exist in the world of ideas. Everything in this world of ours is a participation or an accidental modification of the subsistent ideas." Worldviews have their own methodologies. Curran writes: "The classical methodology tends to be abstract, a priori, and deductive. It wants to cut through the concrete circumstances to arrive at the abstract essence, which is always true, and then work with these abstract and universal essences. In the area of moral theology, for example, the first principles of morality are established, and then other universal norms of conduct are deduced from these." End of section.FREEFree Object ough the concrete circumstances to arrive at the abstract essence which is always true, and then work with these abstract and unniversal essences. In the area of moral theology, for example, the first principles of morality are established, and then other universal norms of conduct are deduced from these." To see the picture of the philosophers mentioned in the text, click on the appropriate button below. End of section.+ CARD:HTl(^n p? Main Menuon mouseUp set scroll of card field 1 to 0 go to Card 2 end mouseUpn ? Sub Menuon mouseUp set scroll of card field 1 to 0 go to Card 91 end mouseUpR o? Back to Texton mouseUp go to card 22 end mouseUp2 8? Protein Synthesis"@ q NnҠ? Figure 1on mouseUp go to card 209 end mouseUpN5? Figure 2on mouseUp go to card 25 end mouseUpN4? Figure 3on mouseUp go to card 212 end mouseUp(Y'(~r:;\]+,6QR\@AyzVW'U']'` PROTEIN SYNTHESIS. The powers of DNA: Replication, Transcription and Translation. REPLICATION. The DNA molecules reside in the nucleus of eukaryotic cells, or in the cytoplasm of the prokaryotes, which have no distinct nuclei. They are organized in the chromosomes by means of histone scaffolding into nucleosome filaments, and then by further folding into chromatine fibers, and finally into chromatids. Much of the DNA carries coded information in form of nucleotide triplets. These are the genetically functional parts of the chromosomes. Every time the cell divides, this coded information, is replicated so that the new cells will have the same coded information. This replication is semiconservative in the sense that each strand of the DNA double helix separates and becomes a template for the assembly of a new strand. This is possible because of the rules of base pairing: adenine-thymine (A-T) and guanine- cytosine (G-C) with two and three hydrogen bonds between the bases respectively. The proof for semiconservative duplication was provided by Meselson and Stahl (1958). They used E. coli bacteria for the study. First they extracted DNA from the cells and subjected the material to buoyant density gradient centrifugation in a solution of cesium chloride. A single band formed showing that the extracted material was homogenous. Next, they provided in the medium of E. coli a heavy isotope of nitrogen, N15, instead of the normal N14. As the cells divided new DNA was formed incorporating the heavy isotope into the bases. When DNA was now extracted and centrifuged, in addition to the old band a new one appeared at a more distant position showing that half of the DNA was made with the heavier isotope of nitrogen. This was possible because half of the DNA material was freshly synthesized during duplication. Click on the Figure 1 button to see the results of this experiment. TRANSCRIPTION. Protein synthesis takes place mostly in the cytoplasm, outside the nucleus in eukaryotes. The nuclear membrane is porous allowing the free passage of smaller or narrower molecules than DNA. Since DNA cannot leave the nucleus, It is necessary to carry the genetic information from nucleus into the cytoplasm by some physical means. The carrier is called the messenger RNA, or mRNA; a single stranded nucleic acid, which can easily pass through the pores of the nuclear membrane. One of the strands of the DNA is used for providing the coded information, which is then transcribed onto the mRNA molecule using the semiconservative replication process (assembly on a given template). At this point the mRNA is useless because in addition to genetic information from the DNA it also including a lot of redundant and meaningless "evolutionary noise". The useless parts, called introns, are cut out of the coded sequence of the mRNA by specific enzymes. Only the meaningful parts, the "exons" remain. Finally the mRNA is provided with a non-coding head at the 5' carbon end to initiate protein synthesis, and a stop signal at the poly A 3' carbon end. While the genetic information of the DNA is called the code, the information on the mRNA is the codon. TRANSLATION. The genetic information carried by the mRNA is translated into amino acid sequence and thus into protein structure in the cytoplasm at the ribosomes. The ribosomes are ribonucleoprotein particles, about 10-20 m_ in diameter. Ribosomes consist of two unequal subunits bound together by magnesium ions. They allow for the pairing of triplets on the mRNA and on the transfer or tRNA. The latter carries a specific amino acid, a package of ATP and a specific enzyme to form the peptide bonds between adjacent amino acids. In this way the primary sequence of amino acids in a protein is determined according to the genetic code. This sequence then will contribute to the secondary (hydrogen bonded _ helix) structure, and ultimately to the tertiary (ionic and covalent bonds between amino acid radicles) and quaternary (hydrophobic and hydrophilic folding) structures of the final protein. Figure 2 shows the major features of the translation process. THE GENETIC CODE. Out of the 64 possible combinations of four nucleotide bases into groups of three (triplets) all but three, UAA, UAG, and UGA, code for amino acids. These three are terminator codons as they stop translation. Since there are only about 20 amino acids to code for, there is a redundancy in the code, which means that several combinations of bases code for the same amino acid. This redundancy is a loss of specificity on the one hand, while, on the other hand, it provides a slight buffer against accidental changes. The meaning of the code is very nearly universal for all living organisms, which may reflect a coherence in the origin of life on earth. The code (shown here in terms of the codon of mRNA) is given below. A = adenine, C = cytosine, G = guanine, and U = uracil. The amino acids are abbreviated to first three letters of their names. First Second Letter Third (5') (3') Letter U C A G Letter U UUU Phe UCU Ser UAU Tyr UGU Cys U UUC Phe UCC Ser UAC Tyr UGC Cys C UUA Leu UCA Ser UAA Term. UGA Term. A UUG Leu UCG Ser UAG Term. UGG Trp G C CUU Leu CCU Pro CAU His CGU Arg U CUC Leu CCC Pro CAC His CGC Arg C CUA Leu CCA Pro CAA Gln CGA Arg A CUG Leu CCG Pro CAG Gln CGG Arg G A AUU Ile ACU Thr AAU Asn AGU Ser U AUC Ile ACC Thr AAC Asn AGC Ser C AUA Ile ACA Thr AAA Lys AGA Arg A AUG Met ACG Thr AAG Lys AGG Arg G G GUU Val GCU Ala GAU Asp GGU Gly U GUC Val GCC Ala GAC Asp GGC Gly C GUA Val GCA Ala GAA Glu GGA Gly A GUG Val GCG Ala GAG Glu GGG Gly G Ala = alanine, Arg = arginine, Asn = aspargine, Asp = aspartic acid, Cys = cysteine, Gln = glutamine, Glu = glutamic acid, Gly = glycine, His = histidine, Ile = isoleucine, Leu = leucine, Lys = lysine, Met = methionine, Phe = phenylalanine, Pro = proline, Ser = serine, Thr = threonine, Try = tryptophan, Tyr = tyrosine, Val = valine. THE OPERON MODEL. Gene function is a highly organized property of the chromosomes. It has been found that this functioning is environment intensive in the sense that genes can be turned on or off according to given environmental conditions. In bacteria there are two types of control over enzyme synthesis: the inducible and the repressible controls. One of the best examples is the response of E. Coli to lactose in its environment. In the absence of this sugar no enzymes are formed. The moment there is sugar available a set of enzymes are synthesized including _-galactosidase, which cleaves lactose into galactose and glucose, _-galactoside permease, which pumps lactose into the cell across the cell membrane, and galactoside-transacetylase whose function is not known for sure. The gene complex known as the operon model (Jacob, and Monod, 1961,) which handles lactose intake and metabolism in E. coli, consists of a regulator gene, operator gene, and several related functional genes, also called cistrons. The regulator is normally combined with a repressor substance, which also has a chemical affinity toward lactose. In the absence of this sugar the regulator gene is inactive and the whole system is shut down. When lactose is present, the repressor substance combines with the sugar and frees the regulator gene. Immediately the adjacent operator gene triggers protein synthesis and thus the enzyme production in all the related cistrons. When the lactose source is exhausted, the repressor again combines with the regulator gene and the system is shut down. It follows from this relationship between various genes that the position of the genes is of great importance. It is functionally important to keep the gene components of the operon close together and protected from separation by crossing over and recombination. The protective mechanism is probably an inversion. (See Main Menu/Chromosome and Gene Mutations/ Chromosome Mutations.) For a diagrammatic representation of the Operon Model click on button Figure 3. End of section.q) q)qFREEFree Object .) For a diagrammatic representation of the Operon Model click on button Figure 3. End of section.@CARD*>.l ? Submenuon mouseUp set scroll of card field 1 to 0 go to Card 20 end mouseUpn p? Main Menuon mouseUp set scroll of card field 1 to 0 go to Card 2 end mouseUp2 8? Allelic Variation"Jn Ā*<   ALLELIC VARIATION. Ever since the work of Gregor Mendel the relationship between the "inherited factors" and the observable "traits" became more and more refined through research. It has been known shortly after Mendelian genetics has been rediscovered in the year of 1900 that Mendel's inherited units were the chromosomes and that the behavior of chromosomes during the first meiotic division underlies the principle of independent assortment of traits. (Sutton and Boveri, 1909, and MacLeod, 1914.) By 1941 Beadle and Tatum refined this relationship in the "One gene-one enzyme" theory. In the early 1950s Hershey and Chase zeroed in on DNA as the hereditary material. Shortly after this, through the work of Wilkins, Franklin, Watson, and Crick, the detailed structure of DNA became known. In the 1960s Chorana and Nirenberg worked out the genetic code showing the connection between nucleotide base triplets of DNA and the primary sequences of amino acids in protein synthesis. Today we look upon the "gene" as a large assemblage of nucleotide pairs along the DNA strands, on the average about 2,000 of them per gene. Change in the code of triplets may occur anywhere in this large assamblage and will result in variations of the gene's performance. In other words, the DNA structure lends itself to the production of a multiplicity of allelic variants. In many instances, this is the case. Take, for example, the white locus (w) in the genome of Drosophila melanogaster. The mutant forms of this gene effect the color of the eye which is normally red produced by the interaction of a bright red and a brownish pigment. Checking the story of this gene in the book "Genetic Variations of Drosophila melanogaster " compiled by Lindsley and Grell, and published by the Carnegie Institution in Washington, we find over 250 allelic variants within this single locus. Depending on the degree the two pigment systems are effected we have white, apricot, Brownex, coffee, coral, colored, eosin, and many more. A similar multiple allelic situation exists at other loci of this species Most of them show between 30 to 50 allelic variants as in case of singed (sn), forked (f), and scute (sc). Since crossing over and recombination are not restricted by the boundaries of genes but can take place within the genes as well, as shown by the Bar eye gene in Drosophila, it is obvious that the multiple allelic series imply an enormous source of genetic variation. Even such simple systems as the ABO blood types with three alleles, the IA, IB, and the i alleles, where IA and IB are codominant to each other and are both dominant over i, provides a complex set of interactions of specific antigenes and antibodies. This, from the point of view of blood transfusions, renders the AB blood type a universal recipient, and the O (ii) blood type a universal donor. Natural selection does not operate directly on alleles but on phenotypes. Since many of the allelic variants may have merit in terms of phenotypes, the rich allelic variation appears in the populations in form of variously useful polymorphs. Polymorphism is a universal characteristic of all that is living on earth. These observations seem to go against the old idea that natural selection, as a rule, tends to weed out variant phenotypes and indirectly establishes the favored allele at a high frequency just under complete fixation. Complete fixation is not attainable because of recurrent mutations decreasing somewhat the frequency of the favored allele. This may be true in some particular cases, but it is certainly not the rule for most systems. End of section.%@FREEFree Object nd of section.@CARD Nl? Main Menuon mouseUp go to Card 2 end mouseUpL ? Submenuon mouseUp go to Card 5 end mouseUp08t? Charles DarwinP? The Voyageon mouseUp go to card 85 end mouseUpZ? The Origin of Specieson mouseUp go to card 86 end mouseUp6  8? Historical BackgroundP 5? Controversyon mouseUp go to card 10 end mouseUpCARDxl? Main Menuon mouseUp set scroll of card field 1 of card 51 to 0 go to Card 2 end mouseUp2 8? Chi-Square Table"Jb Rw? Back to Texton mouseUp go to Card 51 end mouseUpx ? Sub Menuon mouseUp set scroll of card field 1 of card 51 to 0 go to Card 47 end mouseUp& dThe Chi-square Table. Probabilities df | 0.99 0.90 0.80 0.70 0.50 0.30 0.20 0.10 0.05 0.01 1 0.000 0.016 0.064 0.15 0.46 1.07 1.64 2.71 3.84 6.64 2 0.02 0.21 0.45 0.71 1.39 2.41 3.22 4.61 5.99 9.21 3 0.12 0.58 1.00 1.42 2.37 3.67 4.64 6.25 7.82 11.35 4 0.30 1.06 1.65 2.20 3.36 4.88 5.99 7.78 9.49 13.28 5 0.55 1.61 2.34 3.00 4.35 6.06 7.29 9.24 11.07 15.09 6 0.87 2.20 3.07 3.83 5.35 7.23 8.56 10.65 12.59 16.81 7 1.24 2.83 3.82 4.67 6.35 8.38 9.80 12.02 14.07 18.48 8 1.65 3.49 4.59 5.53 7.34 9.52 11.03 13.36 15.51 20.09 9 2.09 4.17 5.38 6.39 8.34 10.66 12.24 14.68 16.92 21.67 10 2.56 4.87 6.18 7.27 9.34 11.78 13.44 15.99 18.31 23.21 15 5.23 8.55 10.31 11.72 14.34 17.32 19.31 22.31 25.00 30.58 20 8.26 12.44 14.58 16.27 19.34 22.78 25.04 28.41 31.41 37.57 25 11.52 16.47 18.94 20.87 23.34 28.17 30.68 34.38 37.65 44.31 30 14.95 20.60 23.36 25.51 29.34 33.53 36.25 40.26 43.77 50.89 CARD%n p? Main Menuon mouseUp set scroll of card field 1 to 0 go to Card 2 end mouseUpl ? Submenuon mouseUp set scroll of card field 1 to 0 go to Card 19 end mouseUp, 8? Chromosomes"Jn N|? Figure 1on mouseUp go to card 234 end mouseUpN{ߠ? Figure 2on mouseUp go to card 235 end mouseUp' CHROMOSOMES. By the end of the nineteenth century, the existence of chromosomes has been well established (Boveri), and in the year 1900, (De Vries, Correns and Tschermak) the connection between Mendelian inheritance and the behavior of chromosomes during the formation of gametes was also known. The name "chromosome" means colored bodies as they have been revealed by special staining techniques. The chromosomes become visible during cell division as they enter the prophase of mitosis or meiosis. This visibility is due to the coiling and supercoiling of associated nucleic acids and proteins. The chromosomes (in the eukaryotic cells) are made of double helical DNA strands (2.0 nm), which coil around histones to form the nucleosome filament (10 nm). Further coiling results in chromatin fibers (30 nm) which are then looped and supercoiled tightly along a protein scaffold. Further coiling of these fibers becomes compacted into the chromatids of the chromosome pairs. The chromatids are thick and quite visible through a high-powered optical microscope. As they can be seen in eukaryotic metaphase chromosomes, the chromatids are doubled and they are joined at the centromere. The centromere is associated with the Kinetochore, the point of attachment to one of the filaments of the microtubular bundle of the centrioles. The position of the centromere determines the overall shape of the chromosomes. If the centromere is at mid point, the chromosome is metacentric (mediocentric). If the upper or p arm is shorter than the lower or q arm, the chromosome is submetacentric. Very short p arm and long q arm results in an acrocentric chromosome. If the centromere is terminal (there being no p arm at all) then the chromosome is telocentric. In the human genome, there are no telocentric chromosomes. Some chromosomes have a small apical portion separated from the rest of the chromosome by a narrow section. This portion is called a satellite. Some of the chromosomes in the human genome may show secondary constrictions (uncoiled, C-banding), which is often polymorphic. (Figure 1.) The best time to photograph the chromosomes is the metaphase when an equatorial plate has been formed. Then all the chromosomes are arranged in the same plane and are in clear focus. The picture is then enlarged and printed, and the individual chromosomes are cut out and arranged according to size and characteristics. This process is knows as karyotyping the chromosomes. The normal human karyotype for females is 46,XX, and for males it is 46,XY. In a human karyotype the chromosomes are arranged in the following groups. Group A. Chromosomes 1-3. These are large metacentric chromosomes, No. 1 being the largest, No. 2 a bit smaller, and No. 3 the smallest in the group. In chromosome 1 a polymorphic secondary constiction may be observed in the proximal region of the q arm. Group B. Chromosomes 4-5. Large chromosomes (4 is longer than 5) with submetacentric centromeres. Group C. Chromosomes 6-12 and the X chromosome. Medium sized submetacentric chromosomes. 9, 10, and 12 are more submetacentric than the others in the group. X resembles No. 6. Group D. Chromosomes 13-15. Medium sized acrocentric chromosomes with satellites on the short (p) arm. Group E. Chromosomes 16-18. Rather short submetacentric chromosomes. No. 16 approximates being metacentric and has a secondary constriction in the proximal part of the long (q) arm. Group F. Chromosomes 19-20. Short metacentric chromosomes. Group G. Chromosomes 21-22 and the Y chromosome. Very short acrocentric chromosomes. Nos. 21 and 22 may have satellites. See Figure 2 for more details. End of section.00FREEFree Object tric chromosomes. Nos. 21 and 22 may have satellites. See Figure 2 for more details. End of section.4 } }FTBL 9Geneva Nadianne!Avant GardeSymbol?Chicago"New Century SchlbkTimes New RomanCharcoal0&!%k@FREEFree Object section.CARDNk? Main Menuon mouseUp go to Card 2 end mouseUp`? Solution of the Controversyon mouseUp go to card 13 end mouseUp`? The Evolutionary World Viewon mouseUp go to card 14 end mouseUp6 8? Historical BackgroundL? Submenuon mouseUp go to Card 5 end mouseUp(9x? EssaysNCARD|jM(6 8? Historical Backgroundnl? Main Menuon mouseUp set scroll of card field 1 to 0 go to Card 2 end mouseUpl ? Submenuon mouseUp set scroll of card field 1 to 0 go to Card 12 end mouseUp89x? Solution of Controversy"Jb M$'M  SOLUTION OF A CONTROVERSY. Either-or makes enemies; and makes friends. Ever since the Oxford Meeting in 1860, when Samuel Wilberforce, the bishop of Oxford, turned to T.H. Huxley and demanded to know whether it was through his grandmother or through his grandfather that he claimed to be descended from the apes (1), the creation versus evolution controversy has been with us. It shows up today in different ways: in newspaper headlines demanding equal rights for those who would teach scientific creationism in schools as an alternative to biological evolution; in textbooks, where no solution is offered but an attempt is made to appeal to partisans on both sides hoping for wider sales. This controversy is full of confusion. The most important sources of confusion are these: The uncritical reliance on assumptions; the misunderstanding of some basic ideas about such issues as the fossil record, the biospecies, and macroevolution; and the identification of the theological contents of the book of Genesis with its temporal wrappings and interpretations. Let us examine these sources of confusion. ASSUMPTIONS are often taken for granted. Sometimes we make an assumption because it is too difficult to investigate a problem, or because we have, for whatever reasons, convinced ourselves that no investigation is required. It is quite a different story when at times we have to make assumptions because it is impossible to obtain any direct information about certain ideas. Such is the case with questions about the origin of life, the nature of the primitive earth, and the meaning of the fossil record. In such cases, however, it is still necessary that through indirect information we make our assumptions as reasonable as possible. The FOSSIL RECORD is another source of confusion. Some people try to use this record as evidence (2), when it is no more than a historical record on a geological time scale about once living organisms. The record is biased, and incomplete, and it is a proof of neither evolution nor creation. It is not legitimate to attempt to prove evolution from the fossil record because without direct observation such proof would imply the proof itself. We can, however, interpret the fossil record in evolutionary terms based upon the reasonable assumption that the evolutionary processes, which we observe today were functional in a similar manner in the distant past. There is a great deal of indirect information needed to render this assumption reasonable, and to provide this information is the task of evolution science. Of course, the same would apply to scientific creationists, who attempt to interpret the fossil record in terms of creation. Another ASSUMPTION, which many people take for granted, is that creation and evolution are two, mutually exclusive phenomena. In a textbook, "Evolution," written by Dobzhansky, Ayala, Stebbins, and Valentine, on page 1 we read: "If man has arrived at his present state as a result of natural processes rather then a supernatural will, he can learn to control these processes." (3). In this seemingly harmless sentence, the assumption that creation and evolution are mutually exclusive is taken for granted, obviously in favor of evolution. Then, the sentence ends with a statement about our ability to control the natural processes, which simply does not follow from the given conditions. Are creation and evolution mutually exclusive? Does creation nullify our ability and freedom of control? These ideas should be investigated, and not just assumed. If the authors of this text are, for whatever reasons, unwilling to investigate these questions, they should not have written the sentence in the first place. Opinions on MACROEVOLUTION vary a great deal in the literature. According to one view, macroevolution and microevolution are two different processes. According to another view, they are really the same because macro evolutionary changes are no more than the accumulations of smaller changes over a longer time. In all these views, macroevolution deals with character states of taxa above the species level. We speak of phyletic evolution, such as the evolution of chordates, or if we are considering class categories, we speak of the evolution of reptiles and mammals. There is a conceptual problem here, a source of confusion. All statements of Charles Darwin on evolution, as he presented them in "The Origin of Species," refer to micro evolutionary changes. (4). The principal factors are variation, the competitive stress due to reproduction in a world of limited resources, and the selective process resulting in the differential survival of the variants. In a dynamic environment, the characteristics of populations are constantly molded through this process into new adaptive forms. These factors can be observed, described, measured, and compared. Consequently, the micro evolutionary process is a well-established, natural phenomenon, and it is effective in producing changes in the structure and composition of populations. There is no question about it, microevolution is real. The reality of microevolution is also indicated by the characteristics of BIOSPECIES. Considering the many species in their natural settings, it becomes clear that to belong to a biological species means to be part of a speciation process. The subdivisions within a natural species reflect the various stages of this process. The geographical races or subspecies, the semispecies, and the superspecies are examples of this. (5). In what way can we speak of PHYLETIC EVOLUTION? Evolution above the species level does not mean the evolution of higher taxonomic ranks but the evolution of character states that we use today to classify living things into ranks above the species. Only by making the reasonable assumption, that the evolutionary processes, which we observe today have been functional in the past, can we speak of phylogenies. According to observation, evolution proceeds on the level of the species, and then, the reasonable assumption would be that the character states, which we use today to classify living organisms into higher taxonomic ranks, were species characters when they were first formed. The older the character state, the higher is its position in our present day system of classification. Taxonomic systems are mental constructs that allow us to bring a logical order into the complex diversity of life on earth. We should remember that life is being lived in groups of individuals that share genes, compete for resources, and are reproductively isolated from others. Only in these terms has the evolutionary process a dimension of reality. Being in touch with reality, as much as possible, is the condition for making reasonable assumptions. The IDENTIFICATION OF A SOURCE WITH ITS INTERPRETATION is a common error and is another major cause of confusion in the creation versus evolution controversy. When Bishop Wilberforce stated at the Oxford Meeting that Darwin's casual theory and sensational opinions on evolution went flatly against the divine revelation of the Bible, he made this error. (6). Nowhere in The Origin can we find a single statement against creation. The contrary is true. In the last sentence of this book Darwin wrote that the beginning of the evolutionary process was the creative act of God. (7). Darwin never said a word in The Origin against any divine revelation, but implicitly he did say a great deal against the nineteenth century interpretation of the first chapters of Genesis. The worldview of his time was static, leaving no room for an evolutionary process. According to this static view, creation and the immutability of species simply had to go together. The Origin contradicts this static interpretation and nothing else. It is not an easy task to keep ideologies, cosmologies and worldviews at bay when we read the book of Genesis. In the textbook on evolution, quoted earlier, we read: "The idea of the permanence of species as special creations entered the Judeo-Christian culture through myths such as those related in the book of Genesis." (8). This statement, to say the least, is unsatisfactory. First, there is not one single word written in the book of Genesis about the permanence of species. Second, it is quite unacceptable, both theologically and historically, to relegate this book to a form of legendary myth-literature of ancient religions. In addition, we should never attempt to interpret a scriptural text of such antiquity as Genesis with an understanding that we base upon twentieth century experiences. The literal interpretation of Genesis is not about words of a modern language. What we need is that we try to understand that time in which this book was written and understood. In an excellent exegetical work on the first three chapters of Genesis, Jean Danilou, a French, Jesuit scripture scholar points out a rather important point about this text. (9). These chapters of Genesis were probably written during the fifth century BC. At that time the Jewish people were surrounded by a great variety of peoples with divers cosmologies and religions. They felt threatened by the pantheistic and polytheistic influences of these peoples. It became necessary to make a clear statement about the Jewish monotheistic position about God, the Creator of all. What has been achieved in these chapters of Genesis was a demythologization of the Oriental, Chanaanite, Babylonian, and Egyptian religions by reducing the various forces of nature from their "divine" status to their natural reality. The Babylonian Tiamt and Marduk, the Egyptian Re, and the Chanaanite Astarte were no longer gods and goddesses but the created ocean, the sun, and the moon. Quite rightly Danilou remarks: "There is a certain air, free from all polytheism, which we breathe in Genesis 1, a wholesome, liberating air." The book of Genesis on creation is truly a demythologizing literature. We should note, however, that the monotheistic statement of Genesis had been presented in images and expressions that we find today to be excessively anthropomorphic. The understanding that we were created in the image of God does not justify the presentation of God in the image of ourselves. Nonetheless, this anthropomorphism is the language of Genesis. (10). God creates in time (six days), and he gets tired by all the labor he has done (the seventh day). I recommend to anyone who wants to appreciate more fully this kind of anthropomorphic presentation, to look at the creation painting by Michelangelo in the Sistine Chapel at the Vatican Museum in Rome. A good reproduction will serve the purpose even better, because then you can enjoy this magnificent painting in peace and comfort, none of which, at least to my experience, are available at the site of the original. Michelangelo presented God in this painting in the classical form of a robed, elderly man, with white flowing hair, and noble features, radiating tremendous intelligence and power. His strong, outstretched arm is only an inch away from the hand of the man he has just created. This is anthropomorphism at its best, but still as such, it is very much bound by all the shortcomings of culture and time. The painting is wonderful, but the way it represents an idea of God is certainly not correct, because it is completely anthropomorphic. Somehow, there is a catch-22 here. We can describe God and speak of the divine act of creation but only in anthropomorphic terms. It is unfortunate that in these terms what we are really describing is not God but ourselves. We speak of God with words that cannot hold him. Can we resolve this problem? I intend to show here that there is a partial solution to this dilemma, and what is more, that this partial solution can also show us the way to a satisfactory resolution of the creation-evolution controversy. It all hinges on our understanding of time, or more precisely, on the way we experience the present moment in the flow of time. The method of approach here is reflexive. We find that the human mind is quite extraordinary in its ability to understand. There are many dimensions to this ability. We understand much more then just the external world that is brought to us by our senses. We are also able to understand abstract ideas, and we can creatively conceive ideas that never existed. On top of all this, the mind is also able to understand itself in a real feat of reflexive actuality. We know ourselves in the same act of knowing. We are aware of ourselves. Without this precious ability we could never experience consciously the present moment, and we would then have no idea of time. As things are, however, we find that self-awareness is a universal and constant experience of the rational human mind. In fact, this awareness is so much a commonplace that we have to reflect on it to experience it explicitly. Then, it provides us with extraordinary insights. I find in my reflexive experience that I am aware of being active right now in this very moment. Of course, such awareness is only possible if my mind in the act of knowing coincides with itself in the same act of knowing. I also find that my awareness is complex because, in the moment of coincidence, I also experience the passage of time as the now inexorably becomes the past. The moment is gone, and so is the intimacy. Instead of being myself, I see myself as an outsider in the mirror of time. Still I know that it is only through the actuality of my awareness that I know all this and can tell about it. I find, therefore, that in my experience of self-awareness there is a real coincidence, but I also find that this coincidence is limited, imperfect, and partial as the actuality of the moment can only be recorded in the flow of time. The relevance of all this for the solution of the controversy is this. In my reflexive awareness, I have a first hand experience with my actuality in which I can form some ideas about both, the perfection and the limitation of being human. I can understand the sources and the characteristics of my anthropomorphism, and I can also formulate some more precise ideas about God. If I were to attempt to look upon the perfection of my reflexive experience, and abstract from its imperfection, I would be experiencing an act of knowing that is in perfect coincidence with itself, absolutely active, absolutely real, in the moment of an absolute present. Then, my experience would be truly divine. Or would it be indeed? I dont really know, because everything I do can only be human. In my ideas, in my words, in the images of my expressions, and in fact, in my very being, I cannot be anything else but anthropomorphic. It stands to reason, however, that when I speak of God, I should attempt to be anthropomorphic by reflecting on my perfection rather than on my limitation. Consequently, I should not say that God created in time, but that God is the Creator of all in the eternal moment of Gods absolute present. There is a tantalizing hint of this concept of positive anthropomorphism in Exodus when Moses said to God, "I am to go, then, to the sons of Israel and say to them, the God of your fathers has sent me to you. But if they ask me what his name is, what am I to tell them?" God said to Moses, "I AM who I AM. This, he added, is what you must say to the sons of Israel, I AM have sent me to you." (11) Michelangelo's creation painting in the Sistine Chapel is beautiful, but it is also anthropomorphic in a negative way. His presentation of God is rooted in the classical and static world-view of the Renaissance. In this view, the material perfection of this world, as it was then understood according to a geocentric and anthropocentric cosmology, reflected the perfection of the Creator. The earth was stationary, and there was nothing new under the sun. No wonder it was so terribly upsetting when Galileo threw the earth, that static and immovable center of the universe, on a spinning course around the sun, destroying the sense of secure geocentric stability. I believe, it must have been equally upsetting to see the intimacy between God and man being threatened by the interposition of such an ordinary and mundane process as Darwin's natural selection. By divesting ourselves from our static, geocentric, and anthropocentric cosmology, we have lost a great deal that was historically precious. As we let these go, we gain an even better truth. We can find in this new perspective a truly deep sense of immediacy and security as we contemplate the absolute, creating presence of God in every moment of every process, be this the process of a human life expressed in years, or the process of evolution of life on earth on a geological time scale. Creation, as a divine act, is not in time, but because we exist in time, we perceive it as a process. Space and time are the created framework of the created world, which we experience in our created way. As theologians, we speak of creation, as scientists, we speak of evolution. We speak in two languages, but of the same reality. It is the divine act of creation, which we experience in every moment of this wonderful process we call evolution. There is no contradiction here! There is no controversy! Is then the solution of the controversy a statement of faith, or is it a matter of science? To answer this question, consider the difference between a scientist, who has faith, and another scientist, who is not a believer. If they are both good scientists, there is no difference between them as far as their science is concerned. The difference is within the persons. Those who believe live in God's presence, and for them the world is meaningful. Those who have no faith experience alienation and loss of meaning. This is most powerfully illustrated by Jaques Monod who in the last sentence of his book, "Chance and Necessity", wrote: The ancient covenant is in pieces; man knows at last that he is alone in the universe's unfeeling immensity, out of which he emerged only by chance." (12). This statement leaves no room for controversy, and it leaves even less room for any possible solution. Such is open only for those who have some expertise in both, faith and science. I know that faith is not given in our genes, and it does not depend on our state of health. I also know that I cannot make people believe by presenting them with a logical argument, even if I know that faith is not against reason, and even if I know that it is far more reasonable to believe than not to believe. Faith is a gift of God. If you want it, ask for it. To ask is already an act of faith. REFERENCES. 1. Moorehead, A. Darwin and the Beagle. 1969. Harper and Row. Page 263. 2. Gish, D.T. Evolution. The Fossils Say No! 1978. Creation-Life Publishers. Preface. 3. Dobzhansky, Ayala, Stebbins, Valentine. Evolution. 1977. W.H. Freeman. Page 1. 4. Darwin. Charles. On the Origin of Species by means of Natural Selection. Random House, Canada, Toronto. 5. Cain, A.J. Animal Species and their Evolution. 1954. Hutchinson's University Library. Pages 86 and 160. 6. Same as (1). 7. Same as (4). Page 374. 8. Same as (3). Page 9. 9. Danilou, Jean. In the Beginning ... Genesis I-III. 1965. Helicon Press. Page 31. 10. Genesis, 1:26-27. The Old Testament of the Jerusalem Bible. Reader's Edition. Vol. 1. Page 18. 11. Exodus, 3:13-15. Same as (10). Page 116. 12. Monod, J. Chance and Necessity. 1971. A. A. Knopf. Page 180. End of essay.0M 19 FREEFree Object (8) Same as (3). Page 9. (9) Danilou, Jean. In the Beginning ... Genesis I-III. 1965. Helicon Press. Page 31. (10) Genesis, 1:26-27. The Old Testament of the Jerusalem Bible. Reader's Edition. Vol. 1. Page 18. (11) Exodus, 3:13-15. Same as (10). Page 116. (12) Monod, J. Chance and Necessity. 1971. A. A. Knopf. Page 180. End of essay.DCARDjBP6 8? Historical Backgroundnl? Main Menuon mouseUp set scroll of card field 1 to 0 go to Card 2 end mouseUpl ? Submenuon mouseUp set scroll of card field 1 to 0 go to Card 12 end mouseUp89x? Evolutionary World View"Jb BL'B1 THE EVOLUTIONARY WORLD VIEW. They bring out of their storeroom new treasures as well as old. Matt. 13:52. A worldview is a comprehensive interpretation of our world. It is the cosmology of a given culture in a given place and time. Up to the middle of the 19th century, the prevalent worldview in the West was static, which emphasized the immutable and the eternal and presented us with unchanging and unchangeable essences. In this view, everything was essentially finished and done according to a timeless plan. Any attempt at change was looked upon in a negative light because it meant a deviation from the original. In this static world, the original was the best, truth was universal, and moral good stood firm for ever for everyone, at all places and at all times. Time and history were mere accidentals in comparison to the never changing, essential realities of life. This view found nourishment in the prevalent classical education of the time in all western schools and universities. Charles Darwin published The Origin of Species In 1859. From that time on we had an alternative world view to consider. After all, if the natural world is a process and we are one of its products, then there is not much point in trying to understand ourselves and our traditions as something unchangeable. What is then important is to understand the process itself that brought us to our present moment, and to figure out the way into our future. The nature of the evolutionary process is fairly well known today. This knowledge is based on such observable features as variation, competition, selection, and some reasonably defined stochastic events. The result of all this is the forever changing adaptive evolution of the many existing species, including our own. The ability of the species to change to the demands of the environment through adaptive responses, and to do that across generations, are the keys of this successful process. There is in this process a positive edge on life. Nothing can survive that is destructive because of the complex interdependence of all living things. Strange as it may seem, but not even competition is destructive because the adaptive response to it is co evolution toward mutual support and interdependence. This is true even in predator-prey and parasite-host relationships. Competition does not result in the monopoly on life gained by one or a few most successful species, but in adaptive radiation, which leads to a multitude of successful, specialized populations and communities. This is the source of the rich variation that we see in nature. (See the essay on Survival of the Fittest in this collection of essays.) The evolutionary process is completely natural and practical. It is simply there to be alive, and to do it well. There are no specific goals to go toward, there are no theories to verify, and principles to live up to. In this process the many opposing factors are simply balanced and maintained close to values, which are the practical best for all concerned. As the conditions of the environment shift and change, so does the meaning of this practical optimum. I am not concerned here to prove the validity of one world view over the other. After all, it is a matter of personal preference, whether we want to perceive our world static as in a snapshot of today, or dynamic as in a movie about our history. My concern is to compare the consequences of our preferences and the way they provide us with insights about certain aspects of human life. Through this comparison, I hope to show that there is more at stake here than just a personal whim about choices of no importance. Consider the following small sample of ideas and experiences. TRADITION. In a static world, tradition means that the tenets of a culture or religion are passed from generation to generation in an atmosphere of conservatism. The parents tolerate no deviations from these tenets in their children. The argument is that the original is the best, and thus, change is detrimental. As to self-image, there is identification between the original and oneself. This identification provides self-esteem, while the absence of change gives a feeling of stability and security. The favorite adage is: Thats the way it must be, because thats the way its always been. Experience belies the validity of such conservatism. Sooner or later, rigid and static traditions will be in conflict with the unavoidable changes in our lives. A common example of such conflict is the painful experience of the generation gap. After all, the younger generation is not the same as the older. In certain issues, the differences between the old and the new may be so great that the heroes of yesterday are without cause and meaning today. The conservative response to changes is often nostalgic. I hear people to say, "It is not like in the good old days," and "I do not know what this world is coming to," implying that, however regrettable it may be, the world has changed. Of course, for the conservative, the changes are for the worse. Yet, life goes on, and often we realize that many changes were for the better. In the evolutionary framework where adaptive changes are welcome, tradition is the element of continuity between successive generations. Members of each new generation have the task to adaptively adjust what they have received from their parents to the somewhat different conditions of their lives. They are expected to be different. To demand rigid adherence to the past would mean the denial of the new and actual needs of the present, a most unrealistic attitude. To have no respect for the past would be equally unrealistic because it is our past that provides the foundations for the range of our present responses. The following quote from a Catechism, first published in the nineteen sixties, most appropriately reflects the evolutionary perspective between generations: Education is service. To treat children as unimportant is to be self-seeking. To regard children as things, which can be turned into copies of ones own person and desires, is also self-seeking. Each child has something special and unique about it. It is a new human being, not a repetition of ourselves. The parents should serve this new life, to set it free to be itself. (A New Catechism. New York, The Seabury Press, 1973. Page 405) The generation gap is not the only painful experience that may be brought about by a static view of life. Violent political changes mark heavily our history. These are expressions of desperate needs, which have not been satisfied by a continuous flow of adaptive adjustments. Unbending adherence to a given status quo in a changing world will eventually lead to painful confrontations. Just as the cause of a violent earthquake is the slow buildup of tensions in the earth's crust, which have not been relieved by a continuous flow of small changes, so it is with the human condition. The evolutionary world view provides us with an adaptive model to avoid such destructive conflicts. HUMAN NATURE. In the static world view, human nature is complete from the first moment of its existence. After all, it is argued, that humanity means certain essential qualities and without these qualities no being can be called human. Consequently, human nature is universal and unchanging. It is the same for everyone who belongs to the human race. It is the same at all times and at all places. Any essential change would destroy our humanity. Development and history are not denied in the static worldview, but they are considered as mere accidentals. This static human nature is also the source and the foundation of natural law, which is then the same for everyone at all places and at all times. Just as human nature is unchangeable, so is natural law unchangeable. Needless to say that human is often understood according to the dominant ethnic image of a given place and culture. In the evolutionary world view, human nature is yet unfinished, open ended. It is not understood as a universal, timeless and essentially static humanness, but as a dynamic evolving reality in the great multitude of individual variations. It is not that each individual somehow participates in an objective blueprint of humanity, but that all of us together in our space and time, are humanity. It is then correct to say according to the evolutionary perspective that human nature is a distribution and it is a process. One refers to the spatial, the other to the temporal meanings of our nature. Our variation is quite impressive. No two human beings are the same. We are all unique individuals, but at the same time, we all belong to the same distribution. Attempts to reduce human nature in its variation to a few common denominators would deny the real richness of the human experience. Human nature is also a process, extending to the entirety of our evolution history, from some unfathomable beginnings to a yet unknown future. This human process is a continuum of changes in which each moment adds something new to a yet unfinished narrative. It is like a tapestry, woven into the reality of a rich pattern by the many actions and decisions of all people everywhere through all history. The evolving human nature is normative. In this context, however, the inherited wisdom of the past is just as much normative as the demands of the present. Furthermore, since we ourselves are the agents of our realization, the process is to that extent self-creative, and natural law is self-determinant. When we say that human nature is open ended, we say the same about the law that flows from our nature. This insight should fill us with gratitude and respect toward our past, and it should instill in us a deep sense of responsibility for our future. COMPROMISE. The ways we look upon our world, static or dynamic, have far reaching consequences. These two views have different methodologies, and they have different values. To illustrate the point, I propose to consider briefly the way we look upon a compromise according to the two views. In a static world, the guiding light in making decisions is the unchanging tradition, which time has distilled into general rules of conduct. These are presented us as ideal principles of life to be followed at all cost and in all circumstances. Our method to arrive at the best choice of action in practical situations is deductive as we compare what we do with the dictates of the ideal. In situations of conflict we may say, as we dig our heels in and refuse to yield, that it is all a matter of principles. Such circumstances of conflict are no more than burdensome nuisances, which we are to overcome. Our task is to preserve the status quo at all costs and to live according to our principles through all sacrifices. This is the stuff that makes heroes, whom we respect. In this context the meaning of compromise is something negative, the act of a coward, whom we despise. In the evolutionary context it is the practical best in the given circumstances that is of value. Here we do not try to live up to an abstract principle but try to assess the concrete situation. In our methodology we follow an inductive path. Through experience we learn to love and respect life, which then becomes our guiding light on the cross roads of choices. In conflict situations, instead of entrenching ourselves for the sake of a principle, we try to strike a compromise between the opposing factors at a value, which is the practical best for all concerned. Natural systems thrive by striking such balances through compromises because such balances provide a positive edge on life. There is nothing negative about a compromise in nature. In the balance of nature a successful compromise reflects a natural wisdom that has been proven successful through millions of years of success. At this point it may be relevant to provide this balance of nature with a touch of realism. A couple of examples may illustrate the practical meaning of compromise in nature. The development of a brood patch is common in nesting birds. This is a highly vascularized, denuded, hot, and very sensitive area of skin. Being in contact with the smooth and cool surface of an egg can alleviate the discomfort of the brood patch. The larger is the egg, the more efficient it is to provide comfort, and in response it will receive more attention and care. Consequently, the chicks in large eggs will develop faster than those in smaller eggs. Increased rate of development is an element of fitness and is under the influence of natural selection. Opposing this selection for larger eggs is the ability of the mother bird to lay them. The actual size of the eggs is the best compromise between the two opposing factors, one of preference, the other of ability. Another example is the pursuing behavior in male grayling butterflies. Mating success is definitely an element of fitness for all sexually reproducing organisms. In the grayling butterfly, mating success depends a great deal on the pursuing behavior of the male toward the female. It is the female who elicits this behavior, and the darker is her coloration, the more efficient is the stimulus she provides. Opposing this selection favoring darker shades is the need to be concealed. The best shade for concealment is a lighter gray. The actual color of the female is a shade of gray that is still concealing and yet it is still effective to elicit the pursuing behavior. Life goes on because of a compromise. HUMAN LIFE. According to the static view, human life is essentially the same for everyone who may be called human. After all, if it were or if it were to become something else, we could not call it human any more. This static, essentially human way of life is expressed in an ideal image. As I live through the many changes of my life, from childhood through adolescence, adulthood and old age, I constantly compare myself with this ideal image, which then reminds me who I and everyone around me should be. This unchanging, monotypic image is the product of my upbringing and represents my parents who demand of me to be like them. In so many ways, this is my conscience, my superego. My love of life is identified with the love of the ideal. Experience shows that falling short of the ideal is a rich breeding ground of feelings of failure, inadequacy, guilt, anger and despair. I may easily become judgmental of others as I condemn them for being different from me, just as I condemn myself for being different from my parents. The image of the ideal I carry in myself may also be the source of other aberrations of judgment. Why should I look upon an unborn fetus as human when it obviously lacks the perfection of the ideal, strong, totally functional, independent and powerful parent image? Why should I look upon those of another race as human when they obviously deviate so much from my monotypic ideal image of humanity in form, language, customs and most other aspects of culture? Human life appears to be quite different in the dynamic, evolutionary perspective. Here, I recognize my life as being a continuous process of changes from the moment of conception until the moment of death. I identify myself with the entire process. I am my entire life. For me to live means to become myself in a unique experience in which I am guided by my past, both genetically and culturally, and at the same time, I am also guided by the demands of the actual circumstances in which I live. My life is open ended. Every moment is a new, small, added detail of realization. As I work toward completion and fulfillment, my choices reflect a love of life that is within me and provides me with values in this process of becoming. The moment of my death is that moment when my life is the most that I can be. I recognize in the evolutionary perspective that my life is different from all other human lives. My uniqueness, however, belongs to the same distribution to which everyone belongs. The distribution of all human lives in space and time defines the total human experience. Because I value the richness of this experience, and I recognize that variation is a condition of survival, I do not demand that others be like me. I accept and support our differences and feel enriched by them because they enrich the same humanity to which I also belong. In the evolutionary view, human life is a process and it is a distribution. Consequently, there is no reason to call any part of human development non-human, just as there is no reason to look upon any part of human distribution as not part of it. Consequently, abortion and racism find no support in the evolutionary perspective. End of essay.1UB@1`FREEFree Object s and it is a distribution. Consequently, there is no reason to call any part of human development non human, just as there is no reason to look upon any part of human distribution as not part of it. Consequently, abortion and racism find no support in the evolutionary perspective. End of essay..CARDC`-Dl? Main Menuon mouseUp set scroll of card field 1 to 0 set scroll of card field 1 of card 4 to 0 go to Card 2 end mouseUp6 8? The Scientific Method"Jb pt? Back to Texton mouseUp set scroll of card field 1 to 0 go to Card 4 end mouseUp-?'-$ THE SCIENTIFIC METHOD. Method is the dressmaker of reality. In this essay, I shall describe in some detail the way scientists use the scientific method. As I pay tribute to the remarkable powers of this method, I shall also consider its limitations. Finally, I shall briefly describe some other non-scientific but, nonetheless, eminently valid encounters with reality. The terminology about science is somewhat confusing. For instance, we come across the expressions, natural science and scientific positivism, suggesting that we also have some kind of unnatural science and scientific negativism as well. Of course, we only have science. We also come across the words, science and technology, as if these two were inseparable. The truth is that they are so different in scope and meaning that they should not be mentioned together at all. We hear often enough the expression science tells us. That is very strange, because science is not someone or something to say anything at all. Scientists, on the other hand, are very talkative people. Scientists pursue the communication of discoveries with passion. So, instead of saying that science tells us this or that, we should accurately report on the discoveries of a specific scientist who, obviously, also has a name. There is no such thing as science tells us even when we are dealing with a strong consensus of a scientific community. The consensus is an experience of sharing knowledge, and it is in the minds of those who do the sharing. In itself, consensus has no independent value or meaning. This last remark seems to run contrary to the idea that consensus, or what we may call the majority opinion, provides us with something special. After all, does not consensus of many improve upon the quality of knowledge over and above the abilities of a single person? Let us consider this for a moment. Consensus may provide me with a sense of support, a feeling that I am not alone in what I think is true, but these have nothing to do with the quality of knowledge. The reason for this is simple enough. Knowledge is fundamentally personal and limited. Even the so-called big picture is just as personal and limited as any other partial knowledge. By the way, the history of science is studded with general agreements about misinterpretations and even errors. Take, for example, the nearly universal acceptance of blending inheritance and the inheritance of acquired characters in the nineteenth century, or recall the even more prevalent geocentric cosmology that lasted through centuries from Aristotle to Galileo. There was certainly no lack of consensus about these issues at the time. They were nonetheless erroneous, and they greatly hindered the process of finding the truth. The quality of knowledge was then and is now just as personal as knowledge itself. The observation that science is a personal, individual venture is further strengthened by the following example. There are many people who are engaged in scientific inquiry. We call them scientists. What they discover is scientific knowledge. The bulk of this knowledge is contained and presented in the many books, and scientific journals we find in libraries. This information is available to anyone who cares to read it. Left alone, this library material is inert knowledge, and it will remain such unless someone takes the trouble to read it and understand it. When this happens, scientific knowledge becomes personal and meaningful, but at the same time it becomes also limited to the abilities of the person who carries this knowledge. The fact that personal knowledge is limited creates a rather interesting paradox. Scientific knowledge is in the heads of individuals, and there is no one who knows it all. To be an expert means to have a lot of partial knowledge, and that is the best we can do. It is like knowing ones way in the woods at a particular place, and to have no first hand knowledge about the rest of the forest. Others know other places, and there is a great deal of overlap and sharing of what we know. It is the scientific community who knows it all, but then we are back to the paradox because knowledge that must be personal and partial to make it come about in the first place can never become impersonal and complete. The scientific community is not a mysterious entity over and above a group of interdependent, but nonetheless individual scientists. It is the individuals effort that makes scientific knowledge grow, and It is the individual who becomes an expert and speaks with authority. Most of the knowledge I call my own is shared knowledge. I went to school and did much reading and listening to obtain it. This process of learning depends on many things, but primarily it depends on my willingness to learn, and on the willingness of others to obtain and communicate their knowledge with me. Besides communication, the interdependence of shared knowledge requires a great deal of both, trust and integrity. Knowledge remains barren without communication, while lack of integrity can be outright damaging. Remember the infamous case of the Janssens Report, and the work and influence of Lysenko. In the former case, racial hatred, in the latter, Marxist ideology was more important than scientific truth. The willingness to share knowledge, and to do it with integrity are also personal qualities of individuals. The nature of scientific knowledge is determined by the method we use to obtain it. The scientific method is a powerful, dialectic process of discovery. It has several stages or steps, each with its special characteristics, powers and limitations. The mainspring of the scientific endeavor is the desire to know. Putting it plainly, scientists are very curious people. It all begins with observation and description of natural phenomena. During this process, many questions arise demanding answers. As the scientist becomes more familiar with the materials observed, the scene is set for some educated guesses as tentative answers to the questions. This is the stage when a hypothesis is put forward. The next stage is the experimental phase of inquiry. The experiment is set up with care to lessen the probability of ambiguous results. Finally, the results of the experiment are statistically evaluated reaching a conclusion in terms of scientific knowledge. The scientific method is a powerful tool of discovery because it definitely leads to knowledge. Even if the results of the experiment refute the original hypothesis, one gets closer to the truth by knowing what is not true. At other times the results may fully support the original ideas, or they may indicate the need for revision and modification. Be as it may, the process of discovery through the scientific method is always progressive and rewarding. Apart from being powerful, the scientific method has also certain limitations, which mostly cluster around some preconceived notions, and follow from the restrictive nature of observation. There are, for example, the preconditioning effects of all that a person already knows. The questions I ask depend on what I have observed, and what I observe is easily biased by the method of observation and by my expectations. The nature of my questions will influence the hypothesis I put forward, and that will affect the way I design my experiments. It is a noble effort to aim at objectivity and to keep an open mind. Still at best, objectivity can be only partially achieved within the limits determined by the characteristics of observation and by the nature of experimental design. Gaps and errors in the fabric of ones scientific knowledge may hinder, slow down, and even mislead the process of inquiry. Sometimes, this kind of handicap becomes firmly established among most members of a scientific community stifling the right approach to discovery for decades and even for centuries. Investigators, who were on the right track, often had to work against the prevalent views of their time, as Galileo, Darwin, and Mendel have done. The restrictive nature of observation, which characterizes the first step in the scientific method, creates another, and a more serious handicap. All scientific studies are limited to the sensory world. We have to see, touch, smell, taste, and hear what we observe. Curiously, sensory perception is a personal affair that has a great deal of subjectivity about it. In addition, the reality of the world that filters through our senses is totally material in character. In science we study exclusively and restrictively the sensory, material world. We cannot resolve this fundamental limitation, not even with the help of technology. Each sense organ has a certain range beyond which much of the material world remains hidden. We may extend the range of our senses by inventing gadgets, such as the telescope, the microscope, time lapse photography and many others. Yet, all these extended observations are still limited and they still remain within the domain of sensory perceptions. Besides being restrictive, the scientific method implies also the need to carry out experiments on a quantifiable basis. The evaluation of experiments requires statistical analysis, and so does the comparison of observations. Through the scientific method we study only those sensory phenomena, which are quantifiable. That is why scientific knowledge is quantitative. To sum this up, the scientific method reveals to us the material world of our senses expressed in terms of quantifiable properties. These characteristics of the method are powerful in revealing a great deal about ourselves and about the world that surrounds us. At the same time, these characteristics also impose some fundamental limitations on the nature of scientific investigation and scientific knowledge. There are a number of other, legitimate approaches to reality besides the scientific. There is, for example, the creative moment of the aesthetic experience, in which the artist actively expresses through powerful emotions the inner perception of reality. This creative, aesthetic moment is exquisitely alive and real. Or think of the experience of the philosophical reflection in which the mind coincides with itself and actually lives the moment of awareness. This reflexive experience through the method of deductive reasoning is a rich source of knowledge. Another legitimate approach to reality is provided by the normative quality of our nature expressed in terms of valid criteria of morality. After all, we are what we do, and what we do is fundamentally influenced by our values. Finally, a fourth, legitimate approach to reality is the faith experience in which we believe the Word of God. For those who have faith, this experience is a unique source of knowledge obtained from the very source of all reality. Some may say that, apart from the scientific, all the other approaches to reality are too subjective to be meaningful. This objection will not stand up because all the experiences that I have mentioned here, including the scientific, have their share of subjectivity, and at the same time, all of them provide an objective reality experience. Of course, by reality I simply mean the way things are to you and to me. Those who would say that there is no other experience of reality but the scientific, grossly and unjustifiably underestimate the depth and the richness of the total human experience. End of essay.FREEFree Object nce of reality but the scientific, grossly and unjustifiably underestimate the depth and the richness of the total human experience. End of essay.l human experience. End of essay.CARDN p? Main Menuon mouseUp go to Card 2 end mouseUp.8? Introduction"@n @CARDx p? Main Menuon mouseUp set scroll of card field 1 of card 4 to 0 go to Card 2 end mouseUp. 8? IntroductionPt? 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Allelic Variationon mouseUp go to card 28 end mouseUp\? Variation and Selectionon mouseUp go to card 27 end mouseUpX? Concealed Variationon mouseUp go to card 29 end mouseUpXL? Measuring Variationon mouseUp go to card 30 end mouseUpCARD# >N p? Main Menuon mouseUp go to Card 2 end mouseUp> :Ӏ? Sources of Genetic VariationL ? Submenuon mouseUp go to Card 18 end mouseUpZ? Chromosome Mutationson mouseUp go to card 33 end mouseUpT? Gene Mutationson mouseUp go to card 32 end mouseUp\? Mutation and Selectionon mouseUp go to card 36 end mouseUp\ C? Evolution of dominanceon mouseUp go to card 37 end mouseUp'CARD&%bn p? Main Menuon mouseUp set scroll of card field 1 to 0 go to Card 2 end mouseUpl ? Submenuon mouseUp set scroll of card field 1 to 0 go to Card 19 end mouseUp4 8? Mitosis and Meiosis"Jn N|? Mitosison mouseUp go to card 236 end mouseUpP{ߠ? Meiosis 1on mouseUp go to card 237 end mouseUpPB? Meiosis 2on mouseUp go to card 238 end mouseUp%]R'= $ % & - * 2  5>$ MITOSIS AND MEIOSIS. In the human situation there are 23 pairs of chromosomes, that is, 46 chromosomes altogether. The members of each pair are homologous, which means that they are similar but they come from two different individuals, the two parents. The number 46 is the full, diploid chromosome number found in the somatic cells of the human body. In contrast, the gametes of the parents, the sperm cells of the father, and the egg of the mother are haploid; they contain 23 chromosomes, half of the original 46. The halving of chromosome number takes place during the formation of gametes. When the gametes unite at fertilization, a zygote is established with the full chromosome complement once again. The events of gametogenesis may be briefly described as follows. The process, which produces the gametes, is called meiotic division. This consists of two cell divisions, meiosis one and meiosis two, but only one nuclear division, because through all this the chromosomes divide only once. In this way, an originally diploid cell produces first two and then four haploid cells. The table below shows in a summary the events, which occur during meiosis I and meiosis II, compared with the events of mitosis, the ordinary form of cell division of somatic cells. The life cycle of a eukaryotic cell from division to division is spent mostly in a metabolically active interphase. During interphase the chromosomes are unwound and spread out inside the nucleus. As the cell enters into mitotic or meiotic cell division a set of characteristic changes and events occur. It is customary to divide these changes and events into four phases: prophase, metaphase, anaphase, and telophase. There are no sharp separations between the phases as they flow into one another in a continuous process. Telophase marks the end of nuclear division, and is then followed by cytokinesis, the division of the cytoplasm and the cell wall, and the even distribution of organelles between the two new cells. The major features of cell division in both, mitosis and meiosis are listed and compared below. PROPHASE METAPHASE ANAPHASE TELOPHASE Mitosis Chromosomes Equatorial Centromeres Chromosomes coil and are plate is divide and reach poles. thick and vi- formed as chromatids Nuclear mem- sible. Centri- spindle fi- move apart brane reforms oles migrate bers shorten followed by to opposite cytokinesis poles, nuclear membrane dissolves and spindle is formed Meiosis Same as above Same as in Centromeres Same as in I In addition, the mitosis do not divide mitosis homologous Homologous chromosomes chromosomes pair; crossing move apart over results in recombina- tion Meiosis Same as in Same as in Same as in Same as in II mitosis mitosis mitosis. Cen- mitosis tromeres di- vide and chro- matids move apart Note: Chromosomes entering division (mitosis, meiosis 1 or 2) have already reached the two-strand stage during interphase as each chromosome has split lengthwise forming two chromatids. The chromatids are held together at the centromeres. In plants, cytokinesis following mitosis also includes the formation of a cellulose wall between the two new cells. The diagrams below compare the four phases of mitosis and. In these diagrams, only a single pair of chromosomes is shown, and for the sake of simplicity, only the nucleus is considered. During mitosis, the nuclear materials are replicated accurately resulting in two identical cells. Only rarely is this accuracy disturbed resulting in somatic mutations. These somatic changes, however, do not affect the germ line. The same cannot be said about meiosis. All genetic changes, which occur during the formation of the gametes will be inherited, provided the gamete in question takes part in fertilization and is incorporated into a viable zygote. While mitosis results in somatic growth, meiosis is the foundation of the formation of gametes. There are two important events associated with this process. One is the reduction of chromosome number by half, which allows for the transmission of genetic information through the union of gametes at fertilization without any increase in chromosome number. The other is the maintenance of genetic variation. In addition to mutations, which provide the raw materials for genetic variation, there is also the event of recombination which provides an additional source of variation. Recombination, which is an exchange of maternal and paternal segments of homologous chromosomes due to a crossing over mechanism, takes place during the prophase of the first meiotic division. The power of recombination as a source of variation is impressive. This can be shown in a simple formula: VG = (r (r + 1)/2)2 where VG is the amount of genetic variation produced by recombination in a genetic system, r is the number of alleles at a given locus, and n is the number of loci effecting the system. Even in a rather simple setup where r = 4, and n = 10, the amount of genetic variation that can be produced by re- combination is in the range of 10 billion. That is why it is said that even without any new mutations, recombination can generate enough genetic variation for natural selection to work on for a long time. One other important aspect that should be clarified is the connection between the events of gametogenesis and the life cycle of a given organism. In the human situation, around the sixth week of embryonic development, a couple of thousand germ cells migrate from a region of the yolk sack to the place where the gonads will be formed. These primordial germ cells, the oogonia in the female, and spermatogonia in the male, greatly increase in number through mitosis. The oogonia and spermatogonia are the diploid precursors of eggs and sperm. In the female infant, there are about half a million oogonia in the two ovaries at the time of birth. This number instead of further increase becomes subjected to a process of depletion in the female. In the male, the multiplication process of spermatogenesis is not confined to a short period of time during embryonic development but it continues throughout life. Another important difference between the female and male reproductive processes is their respective cyclic and non-cyclic nature. The interaction between hormones and the events in the gonads is cyclic at first in both males and females, but the presence of testosterone abolishes all cyclicity in the male before the infant is born. Another difference between oogenesis and spermatogenesis is that in the latter all four products of meiosis one and two become functional gonads while in the development of the egg the distribution of cytoplasm and the nutrients it contains is preferential in favor of one cell only. The first meiotic division thus produces from the diploid primary oocyte a large haploid secondary oocyte and a small haploid polar body. The second meiotic division produces again the large ovum and another small polar body, while the first polar body divides into two more small polar bodies. The end product of all this is one large ovum and three small polar bodies. In the human female the first meiotic division begins during fetal life, but it is then suspended through childhood until the time of the first menstruation during adolescence. It is only when the female gamete is released from the follicle cell that the first polar body is expelled and the cell becomes haploid. When the sperm makes contact with the ovum the second meiotic division takes place and the second polar body is expelled. Fertilization reestablishes the normal diploid chromosome number. It should be noted, however, that fertilization is not a moment in time but it is a process that takes about 36 hours to unfold ending in the mingling of the paternal and maternal genetic materials and the first mitotic division of the zygote. End of section./PFREEFree Object t takes about 36 hours to unfold ending in the mingling of the paternal and maternal genetic materials and the first mitotic division of the zygote. End of section./P`1rm. I FREEFree Object CARD.b,l ? Submenuon mouseUp set scroll of card field 1 to 0 go to Card 21 end mouseUpn p? Main Menuon mouseUp set scroll of card field 1 to 0 go to Card 2 end mouseUp0 8? Gene Mutations"Jn Sk GENE MUTATIONS. Gene mutations are changes in the genetic code. Any change during pairing of bases in the DNA by mishap or replacement will alter the genetic code. This alteration may either code for other than normal amino acid during translation altering the protein structure, or it may become meaningless which then will stop protein synthesis. These are called missense and nonsense mutations. If the change of bases implies a replacement of one purine with another purine or one pyrimidine with another pyrimidine, the mutation is called a transition. If the replacement implies a change from a purine to a pyrimidine or from a pyrimidine to a purine, the mutation is then a transversion. Another kind of gene mutation is the deletion or addition of nucleotides. These will alter the reading reference of the triplet codes resulting in a frameshift mutation. Deletions may be corrected at some other point along the DNA molecule by an addition. This will reestablish the reading reference and will represent a reverse mutation. Since part of the DNA may still be out of phase, the new sequence is called a pseudowild arrangement. A gene consists of many nucleotide pairs along the long DNA molecule in the chromo- somes. This is the biochemical basis for multiple allelic series as illustrated by the white locus (w) in Drosophila which has well over two hundred allelic variants. In the earlier part of the twentieth century investigations focused on single mutations with large phenotypic effects in a simple dominant-recessive relationship giving only two alternatives. The discovery of the fact that most loci provide more than two allelic variants is a later development in genetics. The effects of mutations may range from large and obvious to hardly noticeable small effects. A single amino acid subtitution from glutamic acid to valine at position 6 in the beta chain of hemoglobin results in sickle cell anemia in the homozygous condition. There are probably many alterations of the genetic code without noticeable effects, and many will just slightly alter such features as fitness and viability in the range of semi-lethals and subvitals. There are special methods to detect allelic variants with slight effects on fitness and viability. The best known is the "balancer" method which is able to detect authosomal alleles with slight effects on fitness and viability. To see how this method works select Sub Menu/The Balancer Method. Mutations occur naturally due to ionizing radiations from the sun, including ultra violet radiation, and from radioactive materials in the earth. Some mutations may occur for no other reason than tautomeric shifts due to the normal resonance of a very large molecule. The packaging of the DNA in the chromosomes by histone scaffolding probably considerably reduces the occurrence of this kind of molecular changes. Gene mutations may be artificially induced by X-rays and other high energy radiations, or by the use of chemical mutagens such as mustard compounds and special chelating agents. Administering base analogues, such as 5-bromouracil and 2-aminopurine, can also result in gene mutations. These compounds are incorporated into the base sequence in place of the proper uracil, adenine, or guanine. They fit into the DNA perfectly but they are unspecific as to pairing and will result in a lot of missense and nonsense mutations during replication and transcription. (For the genetic code, see Main Menu/Protein Synthesis.) Gene mutations are rare. For us they are in the range of 1/10000 - 1/100000 per zygote under normal conditions. But on the other hand, there are many genes per person, and there are close to six billion people in the world which makes gene mutations a rather common affair. (See Main Menu/Population Genetics/Mutations for calculations.) End of section.CARD/l ? Submenuon mouseUp set scroll of card field 1 to 0 go to Card 21 end mouseUpn p? Main Menuon mouseUp set scroll of card field 1 to 0 go to Card 2 end mouseUp8 8? Evolution of Dominance"Jn Nt? Figure 1on mouseUp go to Card 249 end mouseUpR>tRS]^hi EVOLUTION OF DOMINANCE. In earlier Mendelian genetics investigations centered on clear cases of single loci with dominant and recessive alleles. The image given by these investigations lead to the idea of a population model where the gene pool consisted mostly of the dominant wild type alleles with a minority of some recessive mutant alternatives. More recent studies have revealed that multiple alleles are the norm and heterozygosity at most loci is common. This recent population model reflects the large amount of genetic variation found at most wild type loci. There are special techniques to assess this amount. One is called the "balancer" method used extensively by Dobzhansky and others. The principle of the "balancer" method is to render an autosomal wild type chromosome homozygous with itself and to see how this effects viability. The idea is that there may be a number of recessive genes along wild type chromosomes with some effect on viability and fitness, but being in heterozygous condition, they remain hidden. Rendering them homozygous, they will show up in the phenotype and can be assessed as to their effect, which is then estimated from a comparison between observed and expected ratios of specific phenotypes. These studies have been originally made by Dobzhansky and Spassky (1963) for the second chromosome in Drosophila pseudoobscura. (See Submenu/Submenu/Genetic Variation/Concealed Variation.) The question here is about the ways an originally recessive gene acquires the characteristics of dominance. It is a general rule that most of the wild type genes are dominant over a multitude of recessive mutant variants. In this arrangement a large amount of genetic variation can be carried in the gene pool as a hidden genetic load. While the dominant wild type genes maintain the status quo of functionality in a given environment of the species, the concealment of mutants in the heterozygotes provides the materials for evolutionary change. It is interesting to see that dominance is really a characteristic of the phenotype and is a product of natural selection. It is not something inherent in the nature of the genes themselves. What is dominant and what is recessive is relative to the genetic background of each particular case. It is known that the relationship between genes and traits is not simple. There is often variation in the phenotypic expression of a single pair of Mendelian genes. This variation comes partly from the environment and partly from polygenic systems which can modify the degree of expression and the amount of occurrence of traits. These phenomena are known as expressivity and penetrance. In a similar manner, polygenic systems may be able to effect the dominant-recessive relationship of alleles. Take, for example, the situation in which the threshold of expression of some gene product depends on a polygenic system of modifier. Suppose that in an allelic pair the a1 allele produces four units of gene products while the a2 allele produces only 1 unit. The production of the homozygous a1a1 genotype will be eight units, that of the heterozygous (a1a2) genotype will be five units, and the homozygous a2a2 genotype will produce only two units. If a polygenic system determines the threshold of sufficiency as four or more units then the a1 allele will be dominant over the a2 allele. On the other hand, if the threshold is at six units then the a2 allele will be dominant over the a1 allele. This statement is based upon the definition of dominance as given below: F (a1a1) = F (a1a2) F (a2a2) which reads: If the phenotype of the (a1a1) genotype is the same as the phenotype of the (a1a2) genotype, and they are both different from the phenotype of the (a2a2) genotype, then the allele a1 is dominant over the allele a2. In case of no dominance all three phenotypes are different. In case of chanbge in teh threshold of sufficiency as indicated in the above examaple, the phenotypic equation will be: F (a2a2) = F (a1a2) F (a1a1) and the dominance relationship will be reversed for the two alleles. See Figure 1 for these relationships. End of section.FREEFree Object l polar body, while the first polar body divides into two more small polar bodies. The end product of all this is one large ovum and three small polar bodies in the female. In the human female the first meiotic division begins during fetal life, but it is then suspended through childhood until the time of the first menstruation during adolescence. It is only when the female gamete is released from the follicle cell that the first polar body is expelled and the cell becomes haploid. When the sperm makes contact with the ovum the second meiotic division takes place and the second polar body is expelled. Fertilization reestablishes the normal diploid chromosome number. It should be noted, however, that fertilization is not a moment in time but it is a process that takes about 36 hours to unfold ending in the mingling of the paternal and maternal genetic materials and the first mitotic division of the zygote. End of section.CARD'pEN p? Main Menuon mouseUp go to Card 2 end mouseUp, 8? TranslationR o? Back to Texton mouseUp go to card 210 end mouseUpN ? Sub Menuon mouseUp go to Card 91 end mouseUpNnҠ? Figure 1on mouseUp go to card 209 end mouseUpN5? Figure 3on mouseUp go to card 212 end mouseUp @BMAPEP1Wm^_4&"3 & #3 & y>>χ|vy    㢁JBO G/@)K /() 0+@P   iTժp l( j+@`2LJp" '"0, # (`i*P#PBp8|>-p[c2d[x/[/`<$/q<.8.㤅z ? k?v?3'2kEJP PLvP 7`08tg7  w> j@ `hTժG"h0N 1ƒ`t&"0@&@xhժ13.P8+$89pk?#886w''$8'(8I:8t  (?I +tI&@x|O5)P (B(H@"I``mj  0H"h? ?Aa+8'$88'(83#(8'(8'0|0 O H #h8>fx8?&#@hB=0 0 0 z % @8=%Hf͆ vvO5(B(E@"gg  0E"?Aa0%00%0 (0000 3$q<0^:- 07$ @ p 0````J*`0```````@ @b 3p `/ / l $. 7+’I$I$I$I$I$i $I$I$I$I%$**4*" ) )&` ) X@))() `(9 rP)9y) 9*@) 9C 9( )V 9P 9 9 X 9#P 9 9 @ )!K9 >iUU_ ) *T2U I$I$I($ÒI$I$I$I$I$I$I$I%p$w' 8zx0x 8zHq 8 #0@=  $=3 8#@R; 8 Rb h0#? "TH 2IRI$&@9,02(@9P;`@2TJ@B(fRh$ &'F bt` *\$0*Y %2@% $dXX@C4&@cBd$o5`p~8|@83 2 8*(3T%}4.TD IH@R&D q80"4#2H@ 9 (%h!Y$I kI$I$I$I$D3300 3333332.@  , D?' 9+  (0 D330`03333333328 '@` 0x D=!!D330"333333332`D1p D330@333333333320%CARDv*$Nn p? Main Menuon mouseUp set scroll of card field 1 to 0 go to Card 2 end mouseUp, 8? Probability"G q n ? Sub Menuon mouseUp set scroll of card field 1 to 0 go to Card 38 end mouseUp$IB<j6 # PROBABILITY. To begin, let us consider some of the basic concepts of probability: the definition of the probability of an event, and the simple relationships of event probabilities according to the rule of multiplication and the rule of addition. These concepts and rules are the foundations of statistical population models which, although simple, are most powerful in showing the effects and interactions of evolutionary factors producing changes in the genetic composition of populations. These changes are truly evolutionary because they are adaptive and they do transcend the limited scope of single generations. The probability of an event, that is P(E), is the number of times an event can occur relative to the total number of possible outcomes. Another word for this is the freqency of an event. Suppose there is a container which has 40 red marbles and 60 white marbles in it. What is the probability to pick one white marble at random? The answer is 60/100 = 0.6. What is the probability to pick a red marble at random? it is 40/100 = 0.4. The rule of addition. In the example above there are only two different kinds of marbles in the container, red and white. The probability of picking either red or white is then the sum 0.6 + 0.4 = 1.0. A probability of 1 is certainty. In a more general form, the probability of an event that can occur in several different ways is given by the sum of the probabilities of the ways it can occur. Suppose that we have in the container in addition to the 40 red and 60 white marbles another 100 blue marbles. Then the probability to pick a red marble is 40/200 = 0.2, while the probability to pick a white marble is 60/200 = 0.3, and to pick a blue marble is 100/200 = 0.5. According to the rule of addition, the probability of picking either a red or a white marble is then 0.2 + 0.3 = 0.5, the sum of the two ways this task can be done. In a formula: P(E1 or E2) = P(E1) + P(E2) The rule of multiplication. The probability of the simultaneous occurrence of two independent events is the product of their probabilities. In a formula: P(E1 and E2) = P(E1) x P(E2) What is the probability to get a double six when we throw two dice? The probability of throwing a six on either dice is 1/6. According to the rule of multiplication, the probability of throwing a double six then is 1/6 x 1/6 = 1/36. By the way, simultaneous is the same as in succession, one after the other. Often we have to combine the two rules of probability, the rule of addition and the rule of multiplication. Here is an example. What is the probability of getting a seven on two dice? There are six ways we can throw seven: 1 and 6, 2 and 5, 3 and 4, 4 and 3, 5 and 2, and 6 and 1. The probability of each of these ways is 1/36, and their sum is 6/36 or 1/6. The probability to throw a seven on two dice is, therefore, 1/6. It is important to keep track of the changing conditions as we calculate probabilities. For instance, what is the probability of pulling an Ace and a King from a deck of 52 cards without replacing the card that we already pulled? The task can be done in two diffdrent ways: we may pull an Ace first and then a King, or we may pull a King first and then an Ace. The probability of each of these events is 4/52 x 4/51 = 6/1000, and the sum of the two probabilities is 12/1000, or 3/250, or 0.012. A simple population model. In the simplest of all population models we consider a single locus (A) with two alleles, which may or may not show dominance. The two alleles are then either (A,a) or (a1,a2) respectively. The gene frequencies of the two alleles are (p, q). Since there are only two alleles, p + q = 1. This population consists of three genotypes which are in case of dominance (AA, Aa, aa) and in case of no dominance (a1a1, a1a2, a2a2). In both of these populations the first and the third genotypes are homozygous, having the same genes as homologues, while the middle or second genotype is heterozygous having two different genes for homologues. The word homologue simply means the two alleles at the same locus, one from the mother and the other from the father. The model, of course, implies that the members of the population are sexually reproducing diploids. In case of dominance, the genotype (AA) is called the homozygous dominant, and the genotype (aa) is the homozygous recessive. The phenotypes of the homozygous dominant (AA) and the heterozygote (Aa) are the same, and they are both different from the phenotype of the homozygous recessive (aa). In case of no dominance, all three phenotypes are different. We calculate gene frequencies by counting the number of a given allele relative to all the alleles at a given locus in a population sample. In a homozygote, there are two of the same allele, while in a heterozygote there is one of each allele. The total number of alleles at a given locus is twice the number of diploid individuals in the population sample. Consequently, the frequency of the dominant allele is p = (2(AA) + (Aa)) / 2N/ In case of no dominance, the frequency of the a1 allele is p = (2(a1,a1) + (a1, a2)) / 2N. Dividing by 2, we can simplify the equations. Then in case of dominance, p = ((AA) + 1/2(Aa)) / N, or in case of no dominance, p = ((a1,a1) + 1/2(a1,a2)) / N. The same calculations will apply to the frequency of the other allele, a or a2, depending on the conditions of dominance. Thus, q = (1/2(Aa) + (aa)) / N, or q = (1/2(a1,a2) + (a2,a2)) / N. Since we consider only two alternatives at a single locus, p + q = 1 and then q = 1 - p, or p = 1 - q. For the sake of simplicity, we may call the three genotypes irrespective of dominance or no dominance (D,H,R). Then p = (D+1/2H)/N and q = (1/2H+R)/N. In case of dominance, the practical problem in determining the gene frequencies in a population sample is the fact that the (AA) and (Aa) phenotypes are the same. How can then we determine the value of p? In such situation, we determine the value of q as the square root of (aa), and then we can determine the value of p as 1 - q. This method will work only for equilibrium populations. A population is in equilibrium if the gene frequencies remain the same from generation to generation. According to the Hardy-Weinberg equilibrium law, in a large, random mating population, and in the absence of mutation, selection and migration, the gene frequencies will remain constant. A population is in equilibrium if 4 DR = H^2, where D means the number of dominants, R the number of recessives, and H the number of heterozygotes in a large population sample. Under such sircumstances, the square root of R will give the value of q and then p = 1-q. It should be remarked, however, that cases of true dominance are relatively rare. In many instances the heterozygous carriers may be detected by ever more sensitive tests. Take for instance hemophilia where the blood clotting time is just a little longer than normal in the heterozygotes. In the case of sicklecell anemia the heterozygous carriers may remain undetected until the system is subjected to some form of extreme stress. Under such conditions some sickling may occur in the carriers. The two rules of probability, the rule of multiplication and the rule of addition, are also useful to calculate genotype frequencies. The probability (or frequency) of homozygous dominants is given as the product of the gene frequency of the dominant gene, that is p^2; while the frequency of the homozygous recessive is q^2. The frequency of the heterozygote is then 2pq because a heterozygous is brought about by the union egg with a dominant gene fertilized by a sperm with a recessive gene, or by the union of an egg with a recessive gene fertilized by a sperm with a dominant gene. Just as the gene frequencies p and q add up to one, the genotype frequencies, (p^2, 2pq, q^2) also add up to one. After all, the sum p^2 + 2pq + q^2 is (p + q)^2, and p + q = i. Another useful function of the rules of chance is to calculate the effect of selection on genotype frequencies. The effect of selection is expressed as the product of the original genotype frequency and the relative adaptive value of the corresponding phenotype. The adaptive value is the measure of survival of a given parental phenotype into the next generation. In addition to the term, adaptive value, the term selection coefficient may also be used. The relationship between these two terms is that adaptive value is (1 - selection coefficient), and selection coefficient is (1 - adaptive value. ) In symbols w = 1-s and s = 1-w where s is the selection coefficient. Adaptive value states what portion of the population remains after selection, while selection coefficient states what portion is taken away by selection. The concept of adaptive value is relative to the best genotype in the population, which has the adaptive value of 1, or more precisely 1 - 0. End of section.CARDW02Ru? Back to Texton mouseUp go to card 71 end mouseUp* 8? TaxonomyLL6j? Algaeon mouseUp go to card 121 end mouseUpPi6? Liverwortson mouseUp go to card 122 end mouseUpR6? Whisk Fernson mouseUp go to card 125 end mouseUpP56S? Seed Fernson mouseUp go to card 129 end mouseUpR6? Club Mosseson mouseUp go to card 126 end mouseUpLR6q? Cycadson mouseUp go to card 130 end mouseUpP 6? Hornwortson mouseUp go to card 123 end mouseUpP 6? Horsetailson mouseUp go to card 127 end mouseUpN p6? Ginkgoson mouseUp go to card 131 end mouseUpL 6? Mosseson mouseUp go to card 124 end mouseUpL 66? Fernson mouseUp go to card 128 end mouseUpNLj?? Coniferson mouseUp go to card 132 end mouseUpTi?? Monocotyledonson mouseUp go to card 133 end mouseUpR?? Dicotyledonson mouseUp go to card 134 end mouseUpN?? Spongeson mouseUp go to card 135 end mouseUpP?? Jellyfishon mouseUp go to card 136 end mouseUpP?? Flatwormson mouseUp go to card 137 end mouseUpN?? Rotiferson mouseUp go to card 138 end mouseUpP7?? Roundwormson mouseUp go to card 139 end mouseUpR5T?? Brachiopodson mouseUp go to card 140 end mouseUpNRq?? Molluscson mouseUp go to card 141 end mouseUpNp?? Annelidson mouseUp go to card 142 end mouseUpPL>jà? Arthropodson mouseUp go to card 143 end mouseUpRiG? Unguiculataon mouseUp go to card 154 end mouseUpRi>à? Echinodermson mouseUp go to card 144 end mouseUpN>à? Lampreyson mouseUp go to card 145 end mouseUpL>à? Sharkson mouseUp go to card 146 end mouseUpT >à? Chondrosteanson mouseUp go to card 147 end mouseUpP!>à? Holosteanson mouseUp go to card 148 end mouseUpR">à? Teleosteanson mouseUp go to card 149 end mouseUpP#>6à? Lungfisheson mouseUp go to card 150 end mouseUpP$5>Sà? Amphibianson mouseUp go to card 151 end mouseUpN%R>qà? Reptileson mouseUp go to card 152 end mouseUpL&p>à? Birdson mouseUp go to card 153 end mouseUpV'G? Glires (Rodents)on mouseUp go to card 155 end mouseUpL(G? Muticaon mouseUp go to card 156 end mouseUpL)G? Feraeon mouseUp go to card 157 end mouseUpR*G? Protungulataon mouseUp go to card 158 end mouseUpR+G? Paenungulataon mouseUp go to card 159 end mouseUpP,6G? Mesaxoniaon mouseUp go to card 160 end mouseUpP-5SG? Paraxoniaon mouseUp go to card 161 end mouseUpN.RpG? Primateson mouseUp go to card 162 end mouseUpJ/oG? Homoon mouseUp go to card 163 end mouseUpP0LjG? Marsupialson mouseUp go to card 164 end mouseUpx1 p? Main Menuon mouseUp set scroll of card field 1 of card 71 to 0 go to Card 2 end mouseUpx2 ? Sub Menuon mouseUp set scroll of card field 1 of card 71 to 0 go to Card 70 end mouseUp@@s`𰰰@FREEFree Object D r l It is easy to see that the stock will maintain itself since neither rD//rD nor rl//rl are viable. Using the "balancer" stock, there are three crosses to be made. In the first cross, wild second chromosomes are brought into the "balancer" stock. The second cross selects one individual second chromosome and makes a number of copies of it. In the third cross the wild second chromosome is rendered homozygous with itself and its viability is assessed. It is a good idea to run a second set of three crosses parallel with the first set. This will allow us to assess the viability of another second chromosome, but also it will make it possible to compare the two selected chromosomes in both, homozygous and he- terozygous conditions. It is better to measure the viability of a homozygous wild type chromosome against a heterozygous wild type situation than against the "balancer" geno- type, even if that comparison is somewhat indirect. Figure 1 below will take you to the card showing the three crosses in a more visual manner. Figure 2 shows how to set up a control cross for comparison. End of Section.CARD,'l ? Submenuon mouseUp set scroll of card field 1 to 0 go to Card 20 end mouseUpn p? Main Menuon mouseUp set scroll of card field 1 to 0 go to Card 2 end mouseUp4 8? Measuring Variation"Jn L|? ANOVAon mouseUp go to card 245 end mouseUpN{ߠ? F Tableon mouseUp go to card 246 end mouseUpӀ2<  x| MEASURING VATIATION. From the point of view of selection and evolution what is important is the between individuals variation in a given trait. If the variation of a trait within the individuals in a sample is as great as its variation between individuals, then selection has no materials to work on, and then there is no adaptive evolutionary change through the generations but only random non adaptive change. The following is a mathematical method to compare the within and between samples variations. The procedures lead to a table of analysis of variance (an ANOVA table.) To see this table, click on button "ANOVA" below. Variance is calculated as the ratio between sum of squares and degrees of freedom. The sum of squares is the sum of the squared deviation of values from their mean, that is, (x - x bar)^2, where x bar is the average of all values, that is, (x)/n. The number of degrees of freedom is always one less than there are values in a sample, that is, n-1. Putting it all together Variance = [(x - x bar)^2]/(n - 1) The following is a practical method to obtain all the required entries for the ANOVA table. A Correction Factor is used to simplify the calculations. First, collect your data by sampling a set of different populations. The larger the sample, the smaller is the sampling error. Collect data several times from the same individuals. A sample of 20-50 measurements per individual is normal. Arrange the data in columns for each sample. Then proceed as follows: 1. Calculate the column totals. (x) 2. Square each item in the samples and calculate the column totals of the squared items. (x^2) 3. Calculate the grand total (T) as the sum of column totals. 4. Calculate the Correction Factor (CF) as T^2/N where N is the total number of measurements in all the samples. 5. Next calculate the total sum of squares by taking the sum of column totals of squared items (obtained in 2 above), and subtract the Correction Factor (obtained in 4 above). 6. Determine the total number of degrees of freedom as N-1. 7. Calculate the between samples sum of squares. First square each column total (obtained in 1 above) to get (x)^2 for each sample. Then add all the squared column totals and divide this sum by n, the number of items in each sample. Finally, subtract the Correction Factor. 8. Determine the between samples number of degrees of freedom as one less than there are samples. 9. Calculate the within samples sum of squares as the difference between the total sum of squares and the between samples sum of squares. 10. Determine the within samples number of degrees of freedom as the difference between total number of degrees of freedom and between samples number of degrees of freedom. 11. Draw up a table of analysis of variance including the sources of variation (Total variation, Between samples variation and Within samples variation), the sum of squares (again as the Total sum of squares, and the Within and Between samples sums of squares), the corresponding degrees of freedom, and the variance esti- mates for between and within samples. The variance estimates are the ratios of a given sum of squares and the corresponding number of degrees of freedom. Cal- culate the variance estimates only for the within and the between samples vari- ances. 12. At this point, you have two variance estimates, one for between samples and one for within samples. One of these will be probably larger than the other. This is called the larger variance estimate, and the other is the lesser variance estimate. Calculate Snedecors F number as the ratio of the larger and the lesser variance estimates 13. Compare this calculated value with the one found in the F table, which you find by clickong on "F Table" below. Take first the F distribution for 0.05 probability. The F value in the table is found at the intersection of the number of degrees of freedom for the larger (columns) and for the lesser (rows) variance estimates. If the calculated F number is less than the one found in the table, then the difference between the two types of variance estimates is not significant. Otherwise, the difference is significant. Significance here means that the probability of coming across such difference by chance alone is five out of a hundred, or one out of twenty. 14. In case the difference between the within and the between samples variations is significant, repeat the above procedure but use the F distribution for 0.01 probability. If the calculated F number is larger than the one found in the table, then the difference between the two types of variance estimates is highly significant. End of section.:CARD9N p? Main Menuon mouseUp go to Card 2 end mouseUpn ? Sub Menuon mouseUp set scroll of card field 1 to 0 go to Card 38 end mouseUp"G q 6 8? Tests of Significance9F W:<BCa!b d!~ !! !"d "j"m "n"x "~" "" """ ## #&&Z&&&''0P0Q0w0{1@1B1d33337 TESTS OF SIGNIFICANCE. This section contains the most common statistical tests we use to compare samples of populations. Two populations are different if the differences between them are significant or highly significant. According to the Null hupothesis, there are differences between two populations but these are produced by chance alone. The measure of "significance" is based on a reasonable convention stating that the more two populations are different statistically the less it is probable that the differences are produced by chance alone. If a given difference may be obtained by chance alone only in one out of twenty cases then the difference is significant. If the given difference may be obtained by chance alone only in one out of hundred cases, then it is highly significant. In this section the described tests of significance are the Chi-square Test, and the Student-t Test. In addition, a third method is also described, called the Least Square Fit method, which may be used to detect trends in a set of data, or to extrapolate data trends into hypothetical values. (The least square fir method described here is relevant for straight line functions only.) The Chi-square Test. Comparing the observed with the expected. The method is particularly useful to evaluate F1, F2, and testcross ratios as well as population parameters in experimental data. The test is sample-size sensitive. Consequently, it can be applied only to actual frequencies and not to percentages. According to some, Chi-square test should be used only if the samaple is fifty or more. An example: The results of a testcross between heterozygous purple stem tomatoes and homozygous recessive green stem tomatoes were 482 purple stem and 526 green stem plants. Do the observed data represent a 1:1 ratio of the two phenotypic classes? In the case of a 1:1 ratio the expected numbers are (482 + 526)/2 = 1008/2 = 504. The calculated value of Chi-square = (d^2/e) where d is the difference between the onserved and the expected, and e is the expected value for each class. For this examaple, e = 504 for each classes. In tabulated form: observed frequencies (o) 482 526 expected frequencies (e) 504 504 d = (o-e) -22 22 d^2 484 484 d^2/e 0.96 0.96 Chi-square = (d^2/e) = 1.92 The next step is to compare this calculated valaue (1.92) with the corresponding value in the Chi-square table at one degree of freedom. (The degrees of freedom is always one less than there are entries in the sample. We have two entries here (482 and 526), therefore the degrees of freedom is one.) Move along the row marked as 1 df (degree of freedom) until you get to or close to the calculated value of 1.92. The corresponding probability is somewhere between 0.20 and 0.10 which means that the difference between the observed and the expected by chance alone is between 0.20 and 0.10. By convention this is not a significant difference and the observed ratio of the two entries may be looked upon as a 1:1 ratio. If the calculated value would have been greater than 3.84 but less than 6.64, then the observed would have been significantly different from the expected. If the calculated value would have been greater than 6.64, then the difference would have been highly significant. Please note again that "significant" means that a given difference between observed and expected occurs in 5 out of 100 cases by chance alone. "Highly significant" means the probability of a difference between observed and expected in 1 out of 100 cases by chance alone. The Chi-square Table. Probabilities df | 0.99 0.90 0.80 0.70 0.50 0.30 0.20 0.10 0.05 0.01 1 0.000 0.016 0.064 0.15 0.46 1.07 1.64 2.71 3.84 6.64 2 0.02 0.21 0.45 0.71 1.39 2.41 3.22 4.61 5.99 9.21 3 0.12 0.58 1.00 1.42 2.37 3.67 4.64 6.25 7.82 11.35 4 0.30 1.06 1.65 2.20 3.36 4.88 5.99 7.78 9.49 13.28 5 0.55 1.61 2.34 3.00 4.35 6.06 7.29 9.24 11.07 15.09 6 0.87 2.20 3.07 3.83 5.35 7.23 8.56 10.65 12.59 16.81 7 1.24 2.83 3.82 4.67 6.35 8.38 9.80 12.02 14.07 18.48 8 1.65 3.49 4.59 5.53 7.34 9.52 11.03 13.36 15.51 20.09 9 2.09 4.17 5.38 6.39 8.34 10.66 12.24 14.68 16.92 21.67 10 2.56 4.87 6.18 7.27 9.34 11.78 13.44 15.99 18.31 23.21 15 5.23 8.55 10.31 11.72 14.34 17.32 19.31 22.31 25.00 30.58 20 8.26 12.44 14.58 16.27 19.34 22.78 25.04 28.41 31.41 37.57 25 11.52 16.47 18.94 20.87 23.34 28.17 30.68 34.38 37.65 44.31 30 14.95 20.60 23.36 25.51 29.34 33.53 36.25 40.26 43.77 50.89 Here is another example: Rothenbuhler in a study of the behavior of hygienic and non hygienic bees obtained four different combinations of behaviors. Since these were the results of a testcross, the expected proportions of the four behavior phenotypes were 1:1:1:1. The observed numbers were 9, 6, 8, and 6. Thus we have: observed (o) 9 6 8 6 expected (e) * 7.25 7.25 7.25 7.25 difference (d) 1.75 -1.25 0.75 -1.25 d^2 3.06 1.56 0.56 1.56 d^2/e 0.42 0.22 0.08 0.22 Chi-square, S(d^2/e) = 0.94 and the corresponding probability at three degrees of freedom is between 0.8 and 0.9, not significant at all. Therefore, the observed numbers represent clo- sely the expected 1:1:1:1 proportions of the four behavior classes. * Note: the expected 1:1:1:1 is obtained as the sum of the observed divided into four equal portions. The total is 29 and 29/4 = 7.25. The Student-t Test. Comparing the means of populations. The mean value of a distribution is a simple parameter in which we look at the central tendency and disregard the characteristics of the variation within the distribution. The Student-t test is able to compare two population in this simplified framework of reference. It is always a good idea to make a sample as large as practically possible. The larger the sample, the smaller is the random sampling error. Sometimes we have several smaller samples and the question may arise whether it would be possible to pool the samples into one or several larger ones to lessen sampling error. Pooling data is possible, provided the pooled populations actually represent the same measured characteristics. The Student-t Test is one of the suitable method to check different populations for "samness". In the Student-t Test the value of t = |D|/sD, where the numerator is the absolute value of the differences between the means of two populations, and the denominator is the standard deviation of the difference of means. To obtain the valaue of t proceed as follows: 1. Assign to one set of data x values and to the other set y values 2. Tabulate your data into six columns: x, x-x bar, (x-x bar)^2, y, y-y bar, and (y-y bar)^2 Calculate the total for each column giving x, (x-x bar) and so on. 3. Calculate the standard deviations: sx = ÷(x-x bar)^2/(N-1), and sy = ÷(y-y bar)^2/(N-1). N is the number of items in each population, that is in each set of data. 4. Next calculate the standard deviations of the means: sx bar = sx/N, and sy bar = sy/N 5. Finally, calculate the value of the standard deviation of the difference of means: sD = sx bar^2 + sybar^2. Now you can calculate the value of t. 6. The final step is to compare the calculated t value with those given in the Students t table for the appropriate number of degrees of freedom which is one less than the number of items in each population. If the calculated t value is less than the one in the table for 0.05 probability, then the two populaltions are not significantly different. If the calculatrd t value is more than the one in the table at 0.05 probability but less than at 0.01 probability, the populations are significantly different. More than 0.01 probability indicate highly significant differences. The Students t table is given below: STUDENTS t VALUES. Degrees of Probability of larger value freedom 0.05 0.01 ______________________________________ 1 12.71 63.66 2 4.30 9.93 3 3.18 5.84 4 2.78 4.60 5 2.57 4.03 6 2.45 3.71 7 2.37 3.50 8 2.31 3.36 9 2.26 3.25 10 2.23 3.17 11 2.20 3.11 12 2.18 3.06 13 2.16 3.01 14 2.15 2.98 15 2.13 2.95 16 2.12 2.92 17 2.11 2.90 18 2.10 2.88 19 2.09 2.86 20 2.08 2.85 22 2.07 2.82 24 2.06 2.80 26 2.05 2.78 28 2.05 2.76 30 2.04 2.75 60 2.00 2.66 120 1.98 2.62 1.96 2.58 The Least Square Fit Method Detecting and extrapolating straight line trends. The method fits a best straight line to a given set of data. The best fit is the one which minimizes the squared deviations between data entries and the corresponding points on a straight line. y = mx + c is the straight line function where m is the slope of the line, and c is the intercept, that is the point where the line crosses the y coordinate. The least square fit method calculates from the given data the values m and c for a best fitting straight line. In a formula: m = xy - (xy/N) and c = (xxy) - (yx^2) x^2 - ((x)^2/N) (x)^2 - Nx^2 To get easily to these calculations tabulate your data into columns of x, y, xy, and x^2, then calculate the column totals as x, y, xy, and x^2. N is the number of (x,y) pairs of plotted data. Finally, using the calculated m and c values construct the straight line to your data which then will be the best fitting straight line. Slanted straight lines may show trends present in the data. Of course, it should be remembered that a straight line is completely determined by two points, and in this case, one of the points should be the value of c, the intercept. It is easy to extrapolate a straight line function by simply continuing the straight line beyond the actual data and reading off from the coordinates the position of the extrapolated point. The least square fit method is the one we are using when we study some of the trends in human evolution. To see an example, go to Main Manu/In the Labaoratory/ Trends in Human Evolution. End of section.aP@tP- CARD}+n p? Main Menuon mouseUp set scroll of card field 1 to 0 go to Card 2 end mouseUp8:? Processes of Speciation"Jm T? Macroevolutionon mouseUp go to Card 251 end mouseUp+RD$016  ' ( 6&1 .:ITfp#$+ANEO+ubw  !!#X#r$s$}%%&y&&&(())i)y*Z PROCESSES OF SPECIATION. For a long time, the concept of species was static, based on morphological similarity according to a single (monotypic) norm of variation. If an organism did not fit the described set of morphological traits, then it was not of the same species. As to taxonomy, the species was the lowest rank of classification. Variations were recognized but they had to remain within a close range to the monotype. Today, we call this kind of species concept the Morphospecies. To see how much the morphospecies concept is inadequate to describe the real diver- sity of life on earth, consider the following exampales: The grackles are black, somewhat larger than thrush sized birds with irridescent colors of green, purple, and bronze. The colors are produced by refracted light and are not due to actual pigments in the feathers. In older field guides to the birds the two types, the purple (Quiscalus quiscula) and the bronzed grackles (Quiscalus versicolor) were described as two different species with a third, the Ridgeway's grackle added to the list. The range of the purple grackle is from north to south on the eastern part of the United States, and that of the bronzed glackle is in an east to west gradient. The two ranges overlap in the north-east where Ridgeway's grackle is found. It turnes out that the purple and the bronzed grackles are of the same species and Ridgeway's grackle is their viable hybrid. The originally two species thus became the subspecies, or geographical races of the same species. It should also be noted that the coloration of the Ridgeway's grackle consists of irridescent bars showing a greater degree of variation that either of the parental purple or bronzed grackles. An increase of variation in the hybrid represents a case of secondary hybridization indicative of some genetic differentiation between the two subspecies. (In case of primary hybridization the intergrading is smooth, without any increse in variation in the hybrid. Primary hybridization indicates a close genetic similarity of the parental populations. Interbreeding between human races is characterized by features of primary hybridization.) The example of grackles shows that a species can be polytypic. The leopard frog (Rana pipiens) is distributed in a north-south gradient in the eastern part of the United States. The vernacular name refers to the coloration of the frog which is green with yellowish spots, while the scientific name refers to the sound of the song they produce. Being an amphibian, the leopard frog is bound to many isolated pockets of water with a somewhat reduced rate of migration between local populations. This fact allows for genetic diversification to develop between different localities. It is interesting to see that adjacent populations show the features of primary hybridization along the entire length of the distribution, but if very distant members of the distribution are brought together artificially, they may not even intergrade at all. To put it simply, populations of the same species which are geogrphically close will intergrade well, while very distant populations will not intergrade at all. The extremes of the distribution are reproductively isolated as if they were not members of the same species. The explanation is that genetic differentiation of adjacent populations are small, but they do add up through distance to a sufficient degree to result in hybrid sterility. We look upon the extreme forms of distribution as belonging to two semispecies of the same species. The concept reflects the dynamic nature of the biospecies. It is a process term, not like the static morphospecies. The distribution of rosella parrots of Australia is the following: Platicercus venustus, north-west; P. icterotis, south-west; P. adscitus, north-east, and P. eximius, south east, including Tasmania. The ranges of these four species of rosella parrots are distinct except for the ranges of P. adscitus and eximius which overlap around Ipswitch and Brisbane. They, however, do not inergrade in this sympatric area but behave as two distinct species. The others do not intergrade because of geographical isolation separated by deserts. Relying on morphological similarities, it may be concluded that the four rosella parrot species are the end of a speciation process and so they are classified into the same Superspecies, the first taxonomic rank above the species. The fruit flies, Drosophila pseudoobscura and D. persimilis are called sibling species because they are close to identical in outward appearance and yet they are repro- ductively isolated in sympatric areas. The isolating mechanism is most likely to be physio- logical and behavioral. There are many examples of sibling species among fruit flies, notably in the D. willistoni group. Other well studied examples are among the mosquitoes in the Anopheles maculipennis and A. gambiae complexes. Considering the above examples, it is concluded that the rank, species, is a process term, it is polytypic, dynamic, and is not the lowest taxonomic rank becasue the processes of speciation require such terms as subspecies or geographical races, semispecies, and sib- ling species, marking the end of speciation by the term superspecies. We call this species concept the biospecies. The primary criterion of specific status is this matter of inter- breeding and producing viable hybrids, or in other terms, it is a matter of reproductive isolation from all other species. Here we do not consider morphology alone but everything living organims provide from genetics to behavior. The best definition to date is: Members of the same biological species are actually or potentially intergrading popula- tions which are reproductively isolated from others. The idea of "potentially" is added because in some instances the isolating mechanims are purely geographical and not genetic. They would intergrade if they could meet. It seems to be logical to say then that to test specific status all we need to do is to bring together in a lab setting the members of geographically isolated groups and see whether they will mate or not, and whether they produce viable hybrids or not. Unfortunately, bringing animals together in artificial setting as in a zoo or in a laboratory is not very relevant because often animals behave abnormally in captivity. The question of what contitutes an isolating mechanism is quite complex. One of the most common types of isolating mechanisms is geograpahical distance which reduces the probability of sharing in a common gene pool. The semiscpecies in Rana pipiens is a good example of that. Once sharing in the same gene pool is limited the probability of genetic differentiation is enhenced by specific, local selection demands. Once the genetic differentiation reaches the point of hybrid sterility, the process becomes irreversible. Of course, the whole concept of reproductive isolation is a process term, and as such it will reflect the various degrees of genetic differentiation. In some cases sterility emerges in the F2, in other cases only one of the sexes is effected while the other remains viable. F1 sterility as in the case of the mule effectively establishes complete isolation of two different but yet somewhat related species. It is customary to classify the various mechanisms of reproductive isolation as pre- zygotic and postzygotic. The prezygotic mechanisms are ecological, seasonal, ethological, mechanical, and gametic. The postzygotic mechanisms are hybrid inviability, hybrid sterility, and hybrid breakdown. Prezygotic mechanisms. Ecological or habitat isolation occurs when species occupy different habitats in the same territory. Examples are the foraging behavior of warblers using statitically different regions of the same pine tree. (MacArthur, 1958) The Cape May warbler forages on tree tops, the Bay-breasted warbler around the mid portion of the trees, and the Myrtle warbler occupies the lower branches and the ground under the tree. In the human situation, the circadian dimorphism of "day" and "night" people with a clar shift in peak activity may be a mild, ecological isolating mechanism. Seasonal or temporal isolation is found between populations in which the members reach sexual maturity, or flowering at different times of the year. This is a common form of isolating mechanism among plants. Ethological isolation may imply a numbr of different mechanisms. Sexual isolation is the breakdown of attraction between the female and the male of related species. The case of sibling species is a good example of that. Initial phases of such sexual isolation can be seen in various mutant strains of fruit flies with reduced reproductive success as illustrated by the loss of attraction between the wild type and the yellow mutant in Drosophla melanogaster. Another ethological isolating mechanism may be presented by the behavior of vectors (such as pollen transferring insects) or the behavior of closely associated symbiotic organisms. The adaptive coevolution of plants and insects is a good example. Mechanical isolation occurs when flower structures develop and prevent pollen transfer, and when structural modifications of genitalia render sperm transfer impossible. Among flowering plants, different species may become specialized to attract different in- sets as pollinators. Gametic isolation occurs when the male and the female gametes fail to attract one another or when the sperm or pollen of one species becomes non viable in the sexual ducts or stigmas and styles of flowers of another species. Postzygotic mechanisms. Hybrid inviability simply means that the hybrid of interspecific crosses fails to develop, is aborted spontaneously, or that it is weak to survive after birth. An example is the sheep x goat crosses where the offsping dies early during embryonic development. In some instances the hybrids, although sterile, exhibit vigor as in the case of mules from horse x ass crosses. Hybrid sterility in interspecific crosses occurs because of disturbances in the pro- cesses of germ-cell formation. The two parental sets of chromosomes often fail to pair during the prophase of the first meiotic division. In some instances the chromosomes assort randomly during meiosis resulting in segregational sterility. Hybrid breakdown. In other instances the "allelic" pairs don't seem to be able to function harmoniously during development resulting in genic or developmental sterility. The former is more common among plants, the latter among animals. End of section. @CARDd4n p? Main Menuon mouseUp set scroll of card field 1 to 0 go to Card 2 end mouseUp0 8? Special Studiesn ? Sub Menuon mouseUp set scroll of card field 1 to 0 go to Card 73 end mouseUp,9v? Molar teethPu? Diagram 1on mouseUp go to card 111 end mouseUp"H q Ptؠ? Diagram 2on mouseUp go to card 112 end mouseUp%BC SPECIAL STUDIES: MOLAR TEETH. The teeth are rather hard parts of the bone structures of vertebrates, and so they are the most likely to remain in the fossil record. In some instances they are the only part we have in the fossil record of a given species. The shape, structure, hight, and cusp patterns of teeth are all relevant to give us some clues about the mode of life, and diet of the animals who had them. Insectivores have sharp needle-like teeth. Primates have short, low cusped molars (bunodont) characteristic to omnivorous diet. Flesh eaters usually have carnassials or modi- fied molars with scissor-like sharp cutting edges. Fish eating aquatic vertebrates have peg shaped molars to catch and hold the prey which they swollow it whole as illustrated by the dentition of alligators, crocodiles, toothed whales and porpoises. Herbivores need a rough tooth surface resisting abrasion caused by the tough cellulose in vascular plants. The typical arrangement is the lophodont teeth where the cusps are high and they fuse into intricate ridges. The simple lophodont dentition of Dinotherium of the Miocene is a good example of such molars. The appearance of complex lophodont arrangement is more recent and it sometimes involves the fusion of several molars into one larger tooth. The com- plex lophodont of modern elephants is an example. Another form of complex lophodont dentition is shown by Artiodactyls (ruminants) and Perissodactyls (horses). Here the arrangement is given by specialized fusion of cusps and by the rearrangement of tooth materials. The outer layer of the tooth is not enamel but cement, a semi hard bone-like material. Underneath the cement is a layer of much folded hard enamel, and below this is the less hard dentine. As the surface wears down by chewing the three materials, enamel, dentine and cement wear at different rates resulting in a very rough grinding surface well suited to break up tough, fibrous plant tissues. In addition, the teeth of these herbivores are tall (hypsodont) and even against heavy wear they last the lifetime of these animals. Click on the buttons, Diagram 1 or Diagram 2, to see the various arrangements. End of section.  ɀ`CARD1{ix ? Submenuon mouseUp set scroll of card field 1 of card 33 to 0 go to Card 21 end mouseUpx p? Main Menuon mouseUp set scroll of card field 1 of card 33 to 0 go to Card 2 end mouseUp6 8? Chromosome MutationsRt? Back to Texton mouseUp go to Card 33 end mouseUpNsנ? Figure 2on mouseUp go to Card 35 end mouseUpN:? Figure 3on mouseUp go to Card 247 end mouseUp BMAPiTh_u 0) " *Ǟ|s>x {n {3f<` {f` n {ϳ>|9 0 9ǟ h  + 4    / |3 /h 3' 3>4+ ! @@D|@|)9⤅~340" 4H" d` %W 1 &04 0(0H2`G<|Hd82a Q3vfv Cz2€ #`@(8 R aqp+("(P'@Sy @-aiih`Z,423@ ?x 4 0( 4`8` 4(0 4( 9# 9J?E(]?Sh4]p8SZ 0S 0h4|?p<``1h4B<Z@y  (00B@h4 B (@n2B(T$24xEh @D0x - m00E$0-)jc``Y 0S 0-[4S @, E\?ST0 0 9995H { )* q 999( :l%C(A (#)10 Wfpp?H&(UU)UTP*(*9[f0`0030009Z`,...$SWDeBf$D`0050E($)8 @`h,---, @$D0f M  ((E0$ WDf 9D⥅HDXD>M?'pP?S?]O? 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Main Menuon mouseUp set scroll of card field 1 of card 39 to 0 go to Card 2 end mouseUp8 :Ӏ? Environmental Variation"Jn N|? Figure 1on mouseUp go to card 211 end mouseUpN{ߠ? Figure 2on mouseUp go to card 248 end mouseUp}J=7C    K\Wpgr$ ENVIRONMENTAL VARIATION. We should never underestimate the importance of the environment in the development and performance of the phenotype. The correlation between the genetic endowment of any organism and its phenotype is never complete. It is true that some traits are more responsive to environmental conditions than others but the image that "It is all in our genes" is both, false and dangerous. To establish the premises, let us first consider a couple of examples of environmental effects. The plant Ranunculus or buttercup grows in marshy areas where often part of the stem and the leaves develop under water. The leaves which grow under water are finely serrated into deep lobes, an arrangement that much increases the relative surface of the leaf and allows for more efficient exchange of carbon dioxide and oxygen between the photosynthetic cells and water. In the air, on the other hand, gaseous exchange is more efficient to start with and the leaves develop as only slightly lobed broad structures with a lesser survace to volume ratio. (See Figure 1) The other example is the coloration of the Himalayan rabbit. The enzyme involved in the production of the pigment melanin is temperature sensitive and functions at temperatures below that of the main mass of the body. Consequently, only the colder parts of the body will become black such as the nose, the ears, the tip of the legs and the tail. The other warmer parts remain white. In both examples the given particular genotype produces different phenotypes purely because of different environmental conditions. In some instances the genetic make-up sets only the limits to a range of variation. The variation of the trait is otherwise environmental. This range of a given genome is known as the "norm of reaction" Here is an examaple. In a study, seven individual plants were collected at random from the same species of the genus Achillea. Each plant was cut into three pieces and the pieces were planted at three different altitudes, one at sea level, another at moderate elevation, that is at 1,400 meters, and the third at high altitude at 3050 meters. Figure 2 shsows the results of this study. The phenotypes of the same genotype are printed one under the other showing a pictorial presentation of the norm of reaction for each of the seven genotypes. It is interesting to see how much variation there is between the genotypes of the same species as to the three environmental conditions. Some people place too much emphasis on the importance of the genetic endowment of individuals or groups of individuals while at the same time play down the importance of the environment. Although genes are important in the production of all inherited aspects of the phenotype, it is not correct to say that they are working alone and independently during development and growth. The phenotype is the result of the interactions between both, genetic and environmental factors, and in some instances it is also clear that these two factors are not independent of each other. (See Submenu/Genetic Variation/Variation and Selection/ last paragraph and Figure 4.) For these reasons a recent book, The Bell Curve, written by Richard Herrnstein and Charles Murray, and published by The Free Press (1994) received rather negative criticism from many scientists. There was an article about this in The Scientific American with the title: For whom the Bell Curve really tolls," meaning the authors of the book. The idea is that emphasis on one of the factors with the neglect of the other leads to serious errors such as racism, a false sense of susperiority, foolish phantasies about a pure gene pool with no genetic load, and so on. There is nothing new about this. Earlier there was the infamous Jensen's Report from Harvard causing a lot of damage in terms of cut goverment supports for education. This report also merited the scorn of the scientific community and resulted in a magnificent response in a book by Richard Lewontin, one of the best population geneticist in the United States, with the title: Not in our Genes! These literary events are the modern expressions of the age old Nurture vs. Nature contorversy. I believe that the best approach to a balanced position in the nature-nurture interactions is what Verle E. Headings has stated: The best results are obtained if we optimize the performance of human genes by providing a rich environment to grow in and thus enhancing all developmental opportunities. (Address to Symposium on Ethical and Social Problems in Human Biology. April 21, 1972. State University of New York, Buffalo. Also see stack: Perspectives on Human Life/Submenu Essays/Genetic Engeneering.) Environmental effects are clearly shown in the following examples: 1. The expression of the mutant gene vestigial (vg) of Drosophila melanogaster is temperature sensitive during development. In higher temperatures (25 - 30C) the expression of the trait strongly overlaps the wild type wings, while in lower temeratures (15 - 20C) the trait is strongly vestigial. 2. In human genetics it is well known that the expression of intellectual impairment in Downs syndrome or 21 trisomy responds considerably to a loving, caring and rich, stimulating environment. The degree of mental retardation is strongly reduced in such environments. 3. Many inherited metabolic disorders respond well to proper environmental modification. Such is the case of galactosemia, phenylketonuria, alkaptonuria, and many others. Take, for instance, glactosemia. A child with this disorder cannot ingest milk which contains the natural milk sugar, galactose. If this sugar is removed from the milk and is replaced by any other sugar such as glucose, fructose, sucrose and so on, the disorder is not expressed at all and the child thrives with no ill effects. Similar are the other two cases related to harmful metabolic effects of phenylalanine. 4. In certain metabolic disorders the harmful effects may be lessened, and some measure of protection may be obtained through appropriate environmental design. Wearing dark glasses, and protecting the body from direct sunlight helps those who suffer from alninism, the lack of formation of the protective pigment melanin. End of section.FREEFree Object eles. Take, for example, the situation in which the threshold of expression of some gene product depends on a polygenic system of modifier. Suppose that in an allelic pair the a1 allele produces four units of gene products while the a2 allele produces only 1 unit. The production of the homozygous a1a1 genotype will be eight units, that of the heterozygous (a1a2) genotype will be five units, and the homozygous a2a2 genotype will produce only two units. If a polygenic system determines the threshold of sufficiency as four or more units then the a1 allele will be dominant over the a2 allele. On the other hand, if the threshold is at six units then the a2 allele will be dominant over the a1 allele. This statement is based upon the definition of dominance as given below: PH (a1a1) = PH (a1a2) PH (a2a2) which reads: If the phenotype of the (a1a1) genotype is the same as the phenotype of the (a1a2) genotype, and they are both different from the phenotype of the (a2a2) genotype, then the allele a1 is dominant over the allele a2. In case of no dominance all three phenotypes are different. In case of chanbge in teh threshold of sufficiency as indicated in the above examaple, the phenotypic equation will be: PH (a2a2) = PH (a1a2) PH (a1a1) and the dominance relationship will be reversed for the two alleles. See Figure 1 for these relationships. End of section.CARD4N p? Main Menuon mouseUp go to Card 2 end mouseUp< 8? Probability and StatisticsR? Probabilityon mouseUp go to card 165 end mouseUpP? Variationon mouseUp go to card 167 end mouseUp\? Tests of Significanceon mouseUp go to card 166 end mouseUp@CARD(\N p? Main Menuon mouseUp go to Card 2 end mouseUpn ? Sub Menuon mouseUp set scroll of card field 1 to 0 go to Card 38 end mouseUp"G q * 8? VariationWR9Be   j  m  % VARIATION. Analysis of Variance: The F-Test. Variation is a fundamental characteristic of all groups of living things. Variation between individuals in a population represents the raw material for natural selection whose operation results in evolutionary changes. The rule is that without variation there is no natural selection, and without natural selection there is no adaptive evolutionary process. That is why in studying evolution the assessment of variation is of importance. What is variation? In mathematical terms, variation is the sum of the squared deviations from the mean divided by the number of degrees of freedom. If there are N data in a sample then the variance equation is like this: s^2 = (x - x bar)^2 / N-1 where s^2 is variance, the sum includes all the measurements from x1 to xn, N is the number of all measurements, x bar is the average x / N, and N-1 is the number of degrees of freedom, one less then all the measurements. The square root of variance is the standard deviation of the distribution. To see the method of measuring and comparing variations, go to Main Menu/In the Laboratory/Study of Variation/Analysis of Variation and F-Tables. Variation in Nature. It should be noted that in evolution studies we are not just concerned about a given variance in a sample but we also need to investigate variation in dynamic terms, that is, changes of variation characteristics of populations in time. We should be also able to assess the adaptive values of amounts of variation in a given changing environment. If the conditions of the environment change rapidly, the amount of variation should be relatively large to be adaptive. If the conditions of the environment are stable, then smaller amounts of variation may proove to be more adaptive. There must be, therefore, some means by which populations may control their variation and achieve and maintain the best value in changing conditions. That is what happens in natural populations. The sources from which variation is increased are mutations and recombination. The mechanisms which decrease variation are natural selection against nonadaptive mutations, and chromosome inversions, which render in inversion heterozygotes the crossing over products non viable. As populations respond to environmental changes, the responses may show a number of general features. In a stable environment the response is often selection against new mutations which represent deviations from the stable conditions. As a result, the tail ends of distribution are pushed toward the mean, variation is reduced, and the population average is the favored phenotype. This situation is called normalizing selection. When the environment changes along the same characteristics for a long time, the populations strive to keep up with the environmental trend and selection favors all new mutations which respond to the changing trends. This is known as directional selection. Of course, the populaltions can only keep up with the environmental changes if they have enough variation to respond. The faster the changes the more there is need for variation. In certain circumstances it is the heterozygote which has selective advantage, as in case of sickle cell anemia. In sickle cell anemia both homozygotes fair less well than the heterozygotes. The homozygous dominants will succomb to malaria, while the homozygous recessives are debilitated by anemia. The heterozygotes, however, are resistant to malaria and at the same time they do not show sickling of erythrocytes under normal circumstances. In such situations the populations predominantly consist of heterozygotes, the frequencies of both alleles will remain high, and many mutations may accumulate being harbored by the heterozygous condition resulting in an increase in genetic load. This condition is known as balancing selection. Finally, if selection is against the heterozygotes, as in the case of Rh incompatibility, we have a genetic mechanism that may lead to the fregmentation of a species into two new species represented by the two homozygotes. This is called disruptive selection. In the human situation, the Rh incompatibility is far from being total as it occurs only in Rh negative women with heterozygous fetuses because the father is Rh positive. Even then the first child will be born without ill effects for the child, but the mother becomes sensitized and the second or third child may be of a problem. Today, by chemical means, we prevent the mother to become sensitized and none of the children will experience any ill effects. End of section.e heterozygotes, there is a tendency toward reduction in variation due to the reduced success of genetic exchange between the homozygotes. End of section.BMAPBM6F]+\# #8 #& 2 B"# B B""@ B B "" B B +E""@ :E J""D"# J4 J2""8%& JH%8 J"""% YY"""#ii""""i$? i""""@3 iC i""""@C> ixx Q ! T" J" #@ Y"""#"0 Y"` """ 00 Hp8 2""8 `  ""  :2 +0# + # +@# + +@ +x J J  <<c c )0" ] )B D Dp  D0 D 8 0  p` `p8 00 `  # HB# !"w? !`xw~wx !fȈ BF"!""%` BwWg" B ? 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L XTxMP. $r.J $T=/ 4#"-/$ "@4 x#".r 4@#".0B5"03" 54\"F "0 E9KI|R@@ T`z4` 9 ft^= d`3` fx W W@ H^ H@ 8 p X X< `x (a # 0\ Z Zp`7t^$cv@ $pvp@E`rg%R@ %8%7F`F`*8`8` ` 8c` `c` :@B  *B  *#p`.⋢8%@a,b>@ y|CAC`gAb&^ "R8DqC,< j,`@R>|yGǟxD R@ 2p@R Cdß<|s" R D$DH"""D)@ @(2&$02t\2R !8#HéAk $yQD "<R R DR` 80` `s  (x@ (~p#<8OQ><(: @"<: Pc<#<pS,x0 8"b#R9>f€ "DD"|BH$H"D 2H &@&p9<x'96l  6s<"xˆ"8B"A?π>ρA2" *p2# H ?UXpB HÀU><e@ )8 Ex>>r(W"D(W"D$(W"D(WDx(FREEFree Object y. It can be shown experimentally that under condi- tions of blending variation between individuals would become soon eroded. Blending leads to sameness. This idea is incompatible with the rich variation we encounter in nature. Materials and methods. Prepare the following items: Two dice of different colors (say red and white); a pocket cal- culator; a few sheets of letter size paper; pen or pencil. On one sheet of paper write Red and the numbers 1 through 6. On another sheet write White and the numbers 1 through 6. The numbers represent the six sides of each die. They also represent the traits of six individuals in each of two groups, reds and whites. The headings of the two sheets of paper would look like these: Red White 1 2 3 4 5 6 1 2 3 4 5 6 Next, throw the two dice one hundred times. Suppose the first throw was 4 on the red and 2 on the white die. Add 4 and 2 and divide the sum by two obtaining the number 3. Write the number 3 under the numbers 4 on the red page and under 2 on the white page. You will have then: Red White 1 2 3 4 5 6 1 2 3 4 5 6 3 3 Suppose the next three throws were 2-5, 4-6, and 6-6. Following the procedures given, and always taking the last entries, these throws will produce the following new values: Red White 1 2 3 4 5 6 1 2 3 4 5 6 3 3 3.5 3.5 4.5 4.5 5.25 5.25 As you can see, the original valaues ranging from 1 to 6 change as the results of blending unfold. When 2 -5 were thrown the calculation is 2 + 5 = 7 and 7/2 = 3.5. So 3.6 is given to the original 2 and 5. When 4 - 6 were thrown the calculation is 3 + 6 = 9, and 9/2 = 4.5. This is because the value of position 4 has already changed to 3 on a previous throw. The 5.25 comes about as the half of the sum of 10.5 from 6 + 4.5. And so on. After a hundred throws, the values will tend to settle close to 3.5. It is a good idea to decide at the very outset of this experiment how many decimal places you are willing to include in the calculated values. Three digits after the decimal point are recommended, with or without rounding off the fourth digit. Thanks to Mendel's discoveries, we know today that the whole idea of blending inheritance is incorrect. The well proven laws of segregation and independent assortment demonstrate the interaction of particulate hereditary factors which definitely remain separate and distinct through the generations. This view of interacting and separate genetic factors became fundamental to our understanding of the genetic sources of variation. Make a graph to show the changes in the phenotypes (numbers). Are the dice really random? End of section.`CARD8 4 ??Study of VariationN p? Main Menuon mouseUp go to Card 2 end mouseUpL ? Sub Menuon mouseUp go to Card 3 end mouseUpX? Variation in Beanson mouseUp go to card 64 end mouseUpR? Draw a Circleon mouseUp go to card 65 end mouseUpZr? Analysis of Varianceon mouseUp go to card 66 end mouseUpNN? F Tableson mouseUp go to card 67 end mouseUp#@CARDq">n p? Main Menuon mouseUp set scroll of card field 1 to 0 go to Card 2 end mouseUp"CU2 .:? Introduction"9 hj+,2   ( ) - . : S l     6Yq`rYKTEN"(\a6<>EGN!!. EVOLUTION. BIOLOGY 245. SYLLABUS AND PROCEDURES. SPRING 2001. General remarks. Bio 245 is a 4 credit course and can only be taken with lab. Classes are TTh 8:30-9:45 Sc.209. Attendance is taken every time we have class. The 4 hours/week lab is to be done M through F in room Sc.310. You should arrange the time of the lab work at your convenience. The lab is kept locked at all times. You will have a key. The lab keys are to be returned by last day of classes. Lab reports should be completed as scheduled. Tests will be announced a week before they are given. There are no makeup tests or early tests. A final paper takes the place of the final exam in this course. This paper is due on the last day of classes. Evaluation of your work. There are four sources to evaluate your work. These are: attendance, tests, lab reports, and final paper. Each test and each lab report are equal in weight with attendance and final paper. Attendance is evaluated as follows: if less than 1/9th of all classes given the semester have been missed an A is given for attendance; if more than 1/9th but less than 2/9th have been missed, the mark is B+ and so on. The evaluation of lab reports is also simple: If everything is OK, but there is nothing special, the mark is B. If something is missed or is unaccurate or is carelessly poresented the mark is C+, C, and so on, depending on the situation. If there is something special, such as extra work that may be relevant to the data and to the conclusions, or the presentation of materials is really impressive, the mark may be raised to B+ or A. As to extra work, a study of the statitical accuracy of data is always welcome. Note. The textbook used in previous years for this course is out of print, and no other is available at this time. Therefore, instead of a textbook, you will be supplied with ample Xeroxed materials. In addition, the entire course has been compiled onto a Hypercard stack named "Evolution" and has been downloaded onto all Macintosh computers in Sc.210. How to access this source from the computers will be shown in class. At the same time, this material is in the process of being transfered from Hypercard to Blackboard. Keep an eye on Blackboard under evolution, Bio 245 to follow the progress. Blackboard is, of course, accessible to all computers via the Internet, including your computer at home. SYLLABUS OF CLASS MATERIALS. 1. Introduction: The scientific method. 2. Historical overview. a. Introduction b. Static World View: Biblical sources: Genesis and Ecclesiastes. Greek philosophical sources: Plato, Aristotle, Ptolemy. Scholastic Medieval sources: St. Thomas Aquinas. The classical renaissance sources. c. Dynamic World View: Copernicus, Kepler, Galileo, Newton, Lamarck, Darwin. d. Darwin: Biography up to the Voyage. Biographical notes of the Voyage. e. The Origin of Species and its statement. Recent advances: Sources of variation. Dedegrees of survival. Random factors. f. Two essays: 1. Macroevolution. 2. The creation/evolution controversy. 3. The genetic structure of populations. a. Historical overview b. The hereditary materials: Proteins and nucleic acids. Chromosomes. Mitosis and meiosis. Genetic code. Genotype and phenotype. c. Genetic variation: Variation and selection. Allelic variation. Concealed genetic variation and fitness. Measuring the amount of genetic variation. Populations and gene pools. d. Sources of genetic variation: Gene mutations. Recombination. Chromosome mutations. Mutation rates. Effects of mutations. Mutation and selection. Evolution of dominance. 4. Natural selection. a. Conceptual overview: Differential survival of variants. Survival of the fittest. Artificial selection. b. The population model: Gene frequencies and genotype frequencies. Hardy-Weinberg equilibrium. Adaptive values. Six selection models. c. Selection and evolution: Directional selection. Normalizing selection. Balancing selection. Disruptive selection. Examples. 5. The processes of speciation. a. The species: Biospecies vs. morphospecies. Agamospecies. Paleospecies. b. The speciation process: Reproductive isolation. Geographical distance. Adaptive radiation. Extinction. c. Trans-specific evolution: The taxonomic hierarchy. Macro vs. micro evolution. Chromosome phylogenies. Protein phylogenies. Mitochondrial RNA. 6. Comparative anatomy. a. Conceptual overview: Homology. Analogy. Chronoclines and morphoclines. Polarity. b. Chordate and vertebrate classification. c. Special studies: Cephalization: jaw suspension, aortic arches, and temporal fossae. Hearts. Kidneys. Fins and limbs. Dentition. 7. The geological record. a. Geochronology: The processes of sedimentation. Relative and absolute time. Correlation of deposits. Index fossils. b. The fossil record: Processes of fossilization. Types of fossils. The nature of the fossil record. c. Overviews: Plants. Vertebrates. Climates. Geological events. Continental drift. 8. Human evolution: The primate connection. Stages of human evolution. Trends in human evolution. FINAL TERM PAPER: Stages and trends in Human Evolution. SYLLABUS OF LAB MATERIALS. 1. Study of variation: Beans Draw a + The human hand. 2. Blending inheritance (simulation). 3. Six population models of selection (Beanetics). 4. Random drift (simulation). 5. Morphoclines (the alphabet, a simulation). 6. Chromosome phylogenies (overlapping inversions, a simulation). 7. Trends in human evolution (skull proportions and projections). ABOUT THIS STACK. The course, Evolution, Bio 245, is presented in this Hypercard stack. It is very simple to navigate the stack by clicking on buttons like the one in the lower right corner labeled Main Menu. Click the button to see how it takes you to the Main Menu, then, once you are there, click the button named Introduction to come back to this card. You will note that as you come back to this card you will be placed at the beginning of the field. On the right of the field you can see a shaded strip called the scroll bar with an up-arrow and a down-arrow at the two ends. Place the cursor (a hand) over the strip where it becomes an arrow pointer. Move the arrow right above the white down-arrow and click the mouse. This will advance the field down by one screen amount of writing. Clicking on the white arrow itself will advance the field by one line. The Main Menu consists of three parts. The ten buttons of the upper stack take you to all the materials we cover in class during the semester. Below this stack are two larger buttons, one named In the Laboratory, the other Self Test. The former takes you to all the lab exercises to be done in this Evolution course. The other button named Self Test opens another Hypercard program for you with test questions and help to find the correct answers. (The self-test program is not finished yet.) There are two more buttons on the Main Menu card. The one named Index takes you to an alphabetical index, the other named Quit exits the program. (The Index is not finished yet). There are also a number of submenues in this stack. They serve to branch out the program into subdivisions of the presented materials. Other buttons, such as Figure, Diagram, Picture etc, help you to find supporting materials. You may print all text from the Hypercard stack. To print, first make sure that the page setup under File is using landscape orientation. Then click on Print Field under File and select the correct field you want. The Blackboard. You need to have an account and a password to get onto Blackboard. Select Evolution, Bio 245, and this will take you to a hierarchy of folders and subfolders. These correspsond to the Menu items in the original Hypercard program. Click on the topic you want to read about, and proceed from there. You may print out any text from this program. Good Luck, and enjoy! PFREEFree Object us, with two allelic alternatives A1 and A2. We call the frequency of the A1 gene p and that of the A2 gene q. In this framework, the value of p is the number of A1 genes in the population relative to the total number of genes at the A locus. Since the homozygous A1A1 genotype has two A1 genes and the heterozygous A1A2 genotype has one A1 gene, the total number of A1 genes in the population is the sum of all homozygous A1A1 genotypes multiplied by two, and all the heterozygous A1A2 genotypes. Similarly, q is the sum of all the A2A2 genotypes times two, plus all the heterozygotes. Since each individual in the population carries two genes at the A locus, the total number of genes at the A locus is twice the number of individuals in the population. Let us call the homozygous A1A1 genotypes D, the heterozygotes H, the homozygous A2A2 genotypes R, and the number of individuals in the population N. Then in an equation: p = (2D + H) / 2N , or p = (D + 1/2H) / N. and q = (1/2H + R) / N The relationship of p and q here is such that p + q = 1 This laboratory exercise is designed to show in a simple manner the fate of genes which are subjected to random genetic drift. The demostration needs some preparation. Nine containers are set up with gene pools of 100 plastic marbles in each. The marbles are of two different colors such as red and white, representing the two different alleles at the studied locus. The gene pools represent a range of gene frequencies from 0.1 to 0.9 with increments of 0.1. This means that the first container will have 90 red marbles mixed with 10 white marbles, the second container will have 80 red and 20 white marbles, the third 70 red and 30 white marbles and so on. If we associate white with gene frequency q, then the frequency of q in the first container is 0.1, in the second container 0.2 and so on. The marbles are now thoroughly mixed in each container. Starting with the container which has q = 0.5, pick 10 marbles at random (without looking). Write down the value of q shown by the sample. Put the marbles back into the container and pick 10 marbles from the container which has the value of q of the previous pick. Repeat this operation as long as it takes to pick a sample of ten marbles of the same color. This means that then q is either equal to 0.0 or to 1.0. Once these values have been reached no further change can take place in the absence of mutations. Plot the changing values of q versus generations on a graph paper. Repeat the experiment a number of times. Press the To Graphs button below to see the results of random drift in four different trials. It may be relevant to repat the experiment with different sample sizes to see the effect of sampling error on the number of generations needed to reach the value of either 0.0 or 1.0 for q. In addition to sample size 10, used in the above experiment, the two other sample sizes were 5, and 15. The following table shows the results: Size of sample Number of generations: from population of 100. (Average) * 5 12 10 14 15 20 * Just for the completeness of the record, the results of the experiments with sample sizes 5. 10, and 15 were the following: Samples of 5 Values of q/generation: 0.5, 0.4, 0.4, 0.4, 0.4, 0.4, 0.8, 0.8, 0.8, 0.6, 0.8, 1.0 0.5, 0.8, 0.8, 0.6, 0.6, 0.6, 0.8, 0.8, 0.6, 0.6, 0.8, 0.8, 1.0 Samples of 10 Values of q/generation: 0.5, 0.4, 0.3, 0.1, 0.1, 0.2, 0.3, 0.2, 0.0 0.5, 0.3, 0.3, 0.4, 0.5, 0.5, 0.6, 0.6, 0.7, 0.6, 0.6, 0.5, 0.4, 0.3, 0.3, 0.3, 0.1, 0.0 0.5, 0.5, 0.5, 0.3, 0.4, 0.6, 0.7, 0.9, 1.0 0.5, 0.4, 0.5, 0.5, 0.4, 0.2, 0.2, 0.3, 0.4, 0.5, 0.5, 0.6, 0.4, 0.3, 0.2, 0.2, 0.2, 0.1, 0.0 Samples of 15 Values of q/generation: 0.5, 0.8, 0.9, 0.7, 0.7, 0.7, 0.8, 0.7, 0.7, 0.7, 0.7, 0.4, 0.3, 0.3, 0.6, 0.4, 0.3, 0.1, 0.2, 0.1, 0.0 0.5, 0.4, 0.5, 0.7, 0.8, 0.8, 0.9, 0.9, 0.8, 0.9, 0.9, 0.9, 0.9, 0.9, 0.9, 0.9, 0.9, 0.9, 1.0 In conclusion, changes in gene frequencies can be introduced by random factors such as sampling error. The smaller is the sample the larger is the sampling error. Since changes in gene frequencies affect the genetic composition of populations, they are evolutionary changes. Natural selection is not the only factor of the evolutionary process. End of section.CARD< L ? Sub Menuon mouseUp go to Card 3 end mouseUp* ??BeaneticsN p? Main Menuon mouseUp go to Card 2 end mouseUpRpH? Introductionon mouseUp go to card 50 end mouseUp`pH? Hardy-weinberg Equilibriumon mouseUp go to card 51 end mouseUpbp H? Complete selection against Ron mouseUp go to card 52 end mouseUp`pSH? Partial selection against Ron mouseUp go to card 53 end mouseUpd G? Partial selection against D & Hon mouseUp go to card 54 end mouseUp` G? Selection against a2 alleleon mouseUp go to card 55 end mouseUp\ G ? Selection in favor of Hon mouseUp go to card 56 end mouseUpX GS? Selection against Hon mouseUp go to card 57 end mouseUpCARD= n : ??Trends in Human Evolutionn p? Main Menuon mouseUp set scroll of card field 1 to 0 go to Card 2 end mouseUp"O n l ? Sub Menuon mouseUp set scroll of card field 1 to 0 go to Card 3 end mouseUpN r? Stage 1on mouseUp go to Card 218 end mouseUpN qՠ? Stage 2on mouseUp go to Card 219 end mouseUpN 8? Stage 3on mouseUp go to Card 220 end mouseUpN 7? Stage 4on mouseUp go to Card 221 end mouseUp ߀B=)8Rp| 8 A  TRENDS IN HUMAN EVOLUTION. The fossil records of both, chordates and invertebrates, present many examples of evolutionary trends. Some well known ones are the increasing complexity of sutures of the nautiloids shells among the molluscs, or among vertebrates the evolution of the limbs and body size in horses. Because of the scarcity of human fossils, it is not an easy task to piece together trends, nonetheless, there are a number of suitable features. The evolution of erect walking and all the changes in the human skeleton associated with it is a good candidate for study. Another is the trend leading the human hand from its involvement in walking as it is seen today among the apes, toward an ever finer instrument of manipulation. There is definitely a trend of increase in brain size through the progressive stages of our evolution accompanied by a number of changes in the skull's relative proportions. This last topic provides us with some more easily accessable materials in the ever changing features of the human skull and gives us an opportunity to have a hands on experience with evolutionary trends. Check on the figures below and you will find the profiles of four human skulls, one from each of our major evolutionary stages. The skulls are Homo habilis, an advanced Australopithecus africanus, from 1.5 million years ago, Homo erectus, from about 0.5 million years ago, Homo sapiens neanderthalensis, dating back to 0.1 million years, and the skull of a modern human, Homo sapiens sapiens at the zero million years point on the evolutionary time scale. The skulls are not drawn to scale, which is of no problem, because we use proportions in this exercise. The only time we use absolute values is when we compare angles between three specific points. First study the skulls carefully in the pictures provided for the four stages below, and then decide on a dozen or so proportions to include in this study. Some of the most obvious proportions could be height versus length of various parts of the skulls, and the sizes of angles measured at three points of some specific parts of the skulls. Your study should also include the lower jaw. The procedure is simple enough. First check out the least square fit method for the straight line function by clicking on Main Menu below and then selecting Probability and Statistics/ Least Square Fit Method. Then take each set of your data and plot the individual entries on a graph with the X coordinate representing time. Fit a straight line function to your graph by the least square fit method and then extrapolate it to the year one million years from today. Note down the extrapolated (x, y) values and the proportions they refer to. Repeat this procedure for all the sets of data you have measured. Finally attempt to reassamble the human skull of the future according to the extrapolated proportions. End of section.ated proportions. End of section.`CARDp)  .  ??Random DriftR  o? Back to Texton mouseUp go to Card 46 end mouseUpL  ? Sub Menuon mouseUp go to Card 3 end mouseUpN  p? Main Menuon mouseUp go to Card 2 end mouseUp BMAP d$iar3KE %4@$%@B%@$%B@w@r@rr@r@r@r@(<%`8 %|$x<84L%x@%b0@& (%`8P%|$||.@$/%|@%b8 (P%`|%x4 -@$0$@%b :(#(##8 4 %`1 %<<4 4d  <  + $  %|  %b8k c( @"" % bH ""S( 9 2 )9 0`A@) `:01* "@:R`|: R< : $; *0:0 x:*` " ;R@*(:b|UmUZ(x( `b8"R9@C(hj41"`$ `sb0@( "%07 @ G @#  %' GP #0`(P" `e0#`&T0 `(0( G# 6` F4C4   'dt@R "@LC @%b(,2)(C("H8B  8)$x ()80`z(`8 ()8E|4@R<  ``  @|`8p88g( ` b "Š("@(@ @ (D%"DH"@D `Ł   `  @ @@K32H302"`0<a 0c$ < 2H 3x(P I@0  38` 0`& H&0@HL 0@ `C3>C<C3|Sxx|ρ<%!@0@ Ǐ8\< 0@DF(DDbB 0GHH$B@ 0@ODB< 0@HDB 0!DDĈDBB 0CC8B< @CARD>~n ? Sub Menuon mouseUp set scroll of card field 1 to 0 go to Card 47 end mouseUpn p? Main Menuon mouseUp set scroll of card field 1 to 0 go to Card 2 end mouseUp< >?Hardy Weinberg Equilibrium"Jl Pw? Chi-Squareon mouseUp go to Card 10 end mouseUpz"?5HI HARDY-WEINBERG EQUILIBRIUM. In a large, random mating population, in the absence of mutation, selection and migration, the gene grequencies remain constant from generation to generation. This is in brief the Hardy-Weinberg Equilibrium Law. It may seem to be trivial to say that if there is nothing to change the frequencies of genes, they remain constant. However, it is of great importance to see where the zero is on an evolutionary scale, because, then, we can measure the magnitude of changes. The first condition requiring a large population is to reduce sampling error. The second condition, random mating, is to exclude mating preferences, such as the advantage of the rare genotype in Drosophila populations. Mutation, selection, and migration are the principal factors producing changes in gene frequencies. The effect of selection can be measured if the other two factors are reduced to zero. In a laboratory setting this is quite possible, since mutations are rare, and migration can be totally eliminated. (See also Main Menu/Natural Selection.) Once tha data have been obtained, we compare the observed results with what we would expect in a Hardy-Weinberg Equilibrium situation. The statistical test will be the Chi-square test. The experiment. In this particular exercise, we take a large random sample of a popula- tion of 200 marbles, 100 blue and 100 red. (For setting up and sampling the population, see Sub Menu/Introduction.) Performing the experiment, the following results were obtained: Sample of 100 picks H H R D R D H H H H H D H R D H H H H H H R R H H R D H H D H D D H H H H H D H H D H H H H D H R R D H H R H R H R D H H D D H R H H R D H H R R R R H H D D H D H H H H H D D R D H H H H H D R D H D q = 0.50 Genotypes D H R Total Observed frequencies (o) 25 55 20 100 Expected frequencies (e) 25 50 25 100 Difference: o -e (d) 0 5 -5 Difference squared (d^2) 0 25 25 d^2/e 0 0.5 1.0 c^2 = d^2/e = 1.5 A Chi-square value of 1.5 with two degrees of freedom means that the differences between the observed and the expected are not significant. By the way, the expected values are computed as the theoretical probability of the three genotyes based exclusively on gene frequencies p and q. The expected genotype frequencies are then p^2, 2pq, and q^2. For the Chi-square table click on the button below. End of section.FREEFree Object D 28 H 58 R 14 5. Apply to this sample the proper conditions of dominance and selec- tion. For instance, if there is dominance and selection is complete against the homozygous recessives, subtract the 14 aa genotypes from the sample. Instead of 100 genotypes, the population total now will be 100 - 14 = 86. Calculating the frequency of q after one generation of selection we have: q1 = (1/2 H + R) / N = (29 + 0) / 86 = 0.34, and p1 = 0.66. Also calculate the change in gene frequency per generation: q = q1 - qo = 0.34 - 0.5 = - 0.16. q is negative because q is decreasing. 6. Adjust the population of 200 marbles according to the new value of q. There should be 68 blue marbles and 132 red marbles in the gene pool according to the new gene frequencies. 7. Repeat this procedure for four generations. Plot the values of q as given by the experiment together with a plot showing the theore- tical values of q under the same conditions. (See Main Menu, Popu- lation Genetics to see the theoretical values.) Plot the experimental and theoretical values of q. 8. Discuss briefly the evolutionary significance of the type of selec- tion presented by the model. (Do you know of any actual examples which correspond to this mode of selection?) 9. Repeat the same set of procedures for all six types of selection. The six types of selection are the following: 1. Complete selection against the homozygous recessive. 2. Partial selection against the homozygous recessive. 3. Partial selection against the homozygous dominant and the hetero- zygote. 4. Selection against the a2 allele when heterozygote is at midpoint. in adaptive value between the two homozygotes. 5. Selection favoring the heterozygote. 6. Selection against the heterozygote. In models 1-3 there is dominance, while in models 4-6 there is no dominance. To see an actual example of any of these selection models, go back to Submenu for choices. End of section. CARD>Ln ? Sub Menuon mouseUp set scroll of card field 1 to 0 go to Card 47 end mouseUpn p? Main Menuon mouseUp set scroll of card field 1 to 0 go to Card 2 end mouseUp< >?Hardy Weinberg Equilibrium"Jl Pw? Chi-Squareon mouseUp go to Card 10 end mouseUpHIn a large, random mating population, in the absence of mutation, selection and migration, the gene grequencies remain constant from generation to generation. This is in brief the Hardy-Weinberg Equilibrium Law. It may seem to be trivial to say that if there is nothing to change the frequencies of genes, they remain constant. However, it is of great importance to see where the zero is on an evolutionary scale, because, then, we can measure the magnitude of changes. The first condition requiring a large population is to reduce sampling error. The second condition, random mating, is to exclude mating preferences, such as the advantage of the rare genotype in Drosophila populations. Mutation, selection, and migra- tion are the principal factors producing changes in gene frequencies. The effect of selec- tion can be measured if the other two factors are reduced to zero. In a laboratory setting this is quite possible, since mutations are rare, and migration can be totally eliminated. (See also Main Menu/Natural Selection.) Once tha data have been obtained, we compare the observed results with what we would expect in a Hardy-Weinberg Equilibrium situation. The statistical test will be the Chi-square test. The experiment. In this particular exercise, we take a large random sample of a popula- tion of 200 marbles, 100 blue and 100 red. (For setting up and sampling the population, see Sub Menu/Introduction.) Performing the experiment, the following results were obtained: Sample of 100 picks H H R D R D H H H H H D H R D H H H H H H R R H H R D H H D H D D H H H H H D H H D H H H H D H R R D H H R H R H R D H H D D H R H H R D H H R R R R H H D D H D H H H H H D D R D H H H H H D R D H D q = 0.50 Genotypes D H R Total Observed frequencies (o) 25 55 20 100 Expected frequencies (e) 25 50 25 100 Difference: o -e (d) 0 5 -5 Difference squared (d^2) 0 25 25 d^2/e 0 0.5 1.0 c^2 = d^2/e = 1.5 A Chi-square value of 1.5 with two degrees of freedom means that the differences between the observed and the expected are not significant. By the way, the expected values are computed as the probability of picking up two marbles of the same color, or of two dif- ferent colors in a hundred trials when the frequencies of both, the blue and the red marbles are the same. For the Chi-square table click on the button below. End of section.+CARDA)0n ? Sub Menuon mouseUp set scroll of card field 1 to 0 go to Card 47 end mouseUpn p? Main Menuon mouseUp set scroll of card field 1 to 0 go to Card 2 end mouseUp> =?Complete selection against R"Jb Lw? Graphson mouseUp go to Card 58 end mouseUp),BM[a N ``r%&( Model 1. Complete selection against the homozygous recessive. Theory. qo = 0.50. Adaptive value of R is 0 Genotypes D H R Total Observed frequencies p^2 2pq q^2 1 * Adaptive values 1 1 0 Frequencies after selection p^2 2pq 0 p^2 + 2pq or 1-q^2 q1 = pq/(p^2 + 2pq) = q/(1+q) q = q1 - qo = -q^2/(1+q) * The Hardy-Weinberg equilibrium frequencies (See Menu/Population Genetics) First generation: H H R R R H H D R H H H R H H H H R D H R D D D D H H H H D D D H D D R H H D H H R H R H R D H H H H D H H R H D H H H D H H R R H H H R H H H H H H D D H R R R H H H R H H D H H H D R H R D H D D D qo = 0.50 Genotypes D H R Total Observed frequencies 24 54 22 100 Adaptive values 1 1 0 Frequencies after selection 24 54 0 78 q1 = (27 + 0)/78 = 0.346 q = q1 - qo = 0.346 - 0.5 = -0.154 The next generation is made of 69 blue and 131 red marbles. Second generation: H D H D H H H D H H R D H H H H R D H D H H D R H D H D H D R H H R R D H D H D H H H D H D D H H H H D H H H H H H D D R H D H H D D H H H H D H H D D R D R D H D D H H D D H D D D H D H H D H D R D q1 = 0.346 Genotypes D H R Total Observed frequencies 38 52 10 100 Adaptive values 1 1 0 Frequencies after selection 38 52 0 90 q2 = (26 + 0)/90 = 0.289 q = q2 - q1 = 0.289 - 0.346 = -0.057 The next population is made of 58 blue and 142 red marbles. Third generation H D D H H H H H D H H H H D D H D D D D D H D D D D D D R D H H D D D H D D H D D H H D H H H H H D D D D H H H H H R D D D D D H R H H H H H H H D D H H H H D R R D H H D D R D H D D D H H H D H D D q2 = 0.289 Genotypes D H R Total Observed frequencies 47 47 6 100 Adaptive values 1 1 0 Frequencies after selection 47 47 0 94 q3 = (23.5 + 0)/94 = 0.25 q = q3 - q2 = 0.25 - 0.389 = -0.039 The next generation is made of 50 blue and 150 red marbles. Fourth generation D D D D D D H H D D D D H D H D D H D D D H D H H H D H R D D H D H R D D D H H D D D H H H H H D D D H H H H D D H D D H D D D D H D H D D H H D D H D H R D R D D H D H H D H D D D H D D R D D D H D q3 = 0.25 Genotypes D H R Total Observed frequencies 57 37 6 100 Adaptive values 1 1 0 Frequencies after selection 57 37 0 94 q4 = (18.5 + 0)/94 = 0.197 q = q4 - q3 = 0.194 - 0.25 = -0.053 Next we compare the observed results with the theoretical values. For the theoretical values of q use the formula qn = qo / (1 + n qo) For the theoretical values of q use the formula q = -q^2/(1 + q), or simply take q = the difference between the values of q in two consecutive generations. For more on theory, see the section: Main Menu/Natural Selection Theoretical values of q and q. Observed values of q and q. qo = 0.50 q qo = 0.50 q q1 = 0.5 / 1.5 = 0.33 -0.17 q1 = 0.346 -0.17 q2 = 0.5 / 2.0 = 0.25 -0.08 q2 = 0.289 -0.08 q3 = 0.5 / 2.5 = 0.20 -0.05 q3 = 0.250 -0.05 q4 = 0.5 / 3.0 = 0.17 -0.03 q4 = 0.197 -0.03 The observed and the theoretical values of q and of q correspond fairly well as shown by the graphs. To see the graphs, click on the button below labeled Graphs. The significance of selection Model 1. The fact that the fitness of the homozygous recessives is zero results in the gradual elimination of the recessive gene from the popu- lation. This is the model of all the harmful recessive mutant genes in a population which are lethal when homozygous. The process of elimination is rapid at first when the initial frequency is high at 0.5, but then it becomes slower as the value of q gets closer to zero. Actually, the gene will not be reduced to zero because of the arrival of new mutations in each generation. It will be reduced to mutation level. As the value of q becomes smaller the H/R ratio increases. At very low values of q the recessive gene will be mostly in the heterozygous condition. End of section.*CARDBB(n ? Sub Menuon mouseUp set scroll of card field 1 to 0 go to Card 47 end mouseUpn p? Main Menuon mouseUp set scroll of card field 1 to 0 go to Card 2 end mouseUp< =?Partial selection against R"Je Lw? Graphson mouseUp go to Card 59 end mouseUp(ǀBKY_  $5&O&t(v Model 2. Partial selection against the homozygous recessive. Theory. qo = 0.50 Genotypes D H R Total Observed frequencies p^2 2pq q^2 1 Adaptive values 1 1 1-s Frequencies after selection p^2 2pq q^2 - sq^2 1-sq^2 because p^2+2pq+q^2 = 1 q1 = (pq + q^2 - sq^2)/(1-sq^2) = q(1-sq)/1-sq^2 q = q1 - qo = -spq^2/(1-sq^2) First generation: R H H H D R D H R R H H D H R H H H R H H H H D D R D H D D D H R H H R H R H R R D H H H H H H D D H H H D H H R H H H D H H D H H R H D R R R R H H D H H H H H R R R H R H R R H H D R H H H D D D R qo = 0.50 Genotypes D H R Total Observed frequencies 22 53 25 100 Adaptive values 1 1 0.5 Frequencies after selection 22 53 12.5 87.5 q1 = (26.5 + 12.5)/87.5 = 0.446 q = q1 - qo = 0.446 - 0.5 = -0.054 The next generation is made of 89 blue and 111 red marbles. Second generation: R H R R D H H D H D H H H D H D H H H D D D R R R H H H D H D D D D H R R H H R H R D D D H R H R D R D D H R H H D R H D H D H H H R D H H H D H D R H R D D H D R H D D H D H D D D H R D H H H H H H q1 = 0.446 Genotypes D H R Total Observed frequencies 35 45 20 100 Adaptive values 1 1 0.5 Frequencies after selection 35 45 10 90 q2 = (22.5 + 10)/90 = 0.361 q = q2 - q1 = 0.361 - 0.446 = -0.085 The next generation is made of 72 blue and 128 red marbles. Third generation D H H R H H H D H H H H H R D H D H H H H D R D H D R R H R H R D D D R H R D D H H D D H H D D H D H R H D H H H D D D H H H D H H D R H H D H H D H H H D D H D D R D R D H H H H H H H R H H D D H D q2 = 0.361 Genotypes D H R Total Observed frequencies 34 53 13 100 Adaptive values 1 1 0.5 Frequencies after selection 34 53 6.5 93.5 q3 = (26.5 + 6.5)/93.5 = 0.353 q = q2 - q3 = 0.361 - 0.353 = -0.008 The next generation is made of 71 blue and 129 red marbles. Fourth generation D H D H H H H H D H H D H D D H H H R R D H D H D H H R H R R H H H H H D D H R D D D D D D H D D H R H H H D D H D D H D D H D H D R H H H D D D D H D D H R H H D H D H H D D D R R D D H D D D D D D q3 = 0.353 Genotypes D H R Total Observed frequencies 46 43 11 100 Adaptive values 1 1 0.5 Frequencies after selection 46 43 5.5 94.5 q4 = (23.5 + 5.5)/94.5 = 0.307 q = q4 - q3 = 0.307 - 0.353 = -0.046 Next we compare the observed results with the theoretical values. For the theoretical values of q use the formula q1 = qo(1-sqo)/(1-sq^2). The formula for q is -spq^2/(1-sq^2), or simply take q = the difference between the values of q in two consecutive generations. Remember that each generation is calculated from the values of the previous generation. For instance, q2 = q1(1-sq1) and so on. For more about the theoretical values see the section: Main Menu/Natural Selection. Theoretical values of q and q. Observed values of q and q. qo = 0.500 q qo = 0.500 q q1 = 0.429 -0.071 q1 = 0.446 -0.054 q2 = 0.371 -0.058 q2 = 0.361 -0.085 q3 = 0.324 -0.047 q3 = 0.353 -0.008 q4 = 0.287 -0.037 q4 = 0.307 -0.046 The observed and the theoretical values of q and of q correspond fairly well as shown by the graphs. Click on the button below labeled Graphs to see the graphs. The significance of selection Model 2. The model represents the situation where the homozygous recessives are not lethal but there is selection against them. This is the case in many recessive mutant genes. In this particular model the adaptive value (1-s) is 0.5 which simply means that half of the homozygous recessives will survive. Otherwise the model is similar to the previous one except that everything happens a bit more slowly. Since q is negative, the frequency of the recessive gene will be eventually reduced to mu- tation level. End of section.+CARDC(n ? Sub Menuon mouseUp set scroll of card field 1 to 0 go to Card 47 end mouseUpn p? Main Menuon mouseUp set scroll of card field 1 to 0 go to Card 2 end mouseUp> ??Partial selection against D&H"Jb Lw? Graphson mouseUp go to Card 60 end mouseUp> ??Partial selection against D&H(JHV]bs  L]&&;''( Model 3. Partial selection against the dominants. Theory. qo = 0.50. Adaptive values of D and H are 0.5 Genotypes D H R Total Observed frequencies p^2 2pq q^2 1 Adaptive values 1-s 1-s 1 Frequencies after selection p^2(1-s) 2pq(1-s) q^2 1-sp(1+q) q1 = q(1-sp)/(1-sp(1+q)) q = spq^2/(1-sp(1+q)) First generation: H H D H R R D H H D H H H H H R H D D R H R D R R H H H D H H H H D H H H H D H D H R H R H D D H H R D H D D H H H D D H H D H H H H R H H H H D H H R H D H H H D D D H R R H R R R R H R H R H H H D qo = 0.50 Genotypes D H R Total Observed frequencies 24 56 20 100 Adaptive values 0.5 0.5 1 Frequencies after selection 12 28 20 60.0 q1 = (14 + 20)/60 = 0.567 q = q1 - qo = 0.567 - 0.5 = 0.067 The next generation is made of 113 blue and 87 red marbles. Second generation H H D D H R R H H H H H H D R D D R R H R H R H D H D R H H D R H D H H H H D H H D R D H R D R R D D H H R H H R H R R H H R D H H H H D D R H R R R H H R R H H H H R R H H H H H R D H R D H H H H D q1 = 0.567 Genotypes D H R Total Observed frequencies 21 51 28 100 Adaptive values 0.5 0.5 1 Frequencies after selection 10.5 25.5 28 64 q2 = (12.75 + 28)/64 = 0.637 q = q2 - q1 = 0.637 - 0.567 = 0.07 The next generation is made of 127 blue and 73 red marbles. Third generation: D D R R H R H H H H D R H R D R H R H H R D R R R R R R R H H R H R H D H H H R H D H D R R H R R R H H D H H H H H H R D H H R R D H H H H R H H H D D H R D D H H R R H R H H D R R H R H R R H R D R q2 = 0.637 Genotypes D H R Total Observed frequencies 17 46 37 100 Adaptive values 0.5 0.5 1 Frequencies after selection 8.5 23 37 68.5 q3 = (11.5 + 37)/68.5 = 0.708 q = q3 - q2 = 0.708 - 0.637 = 0.071 The next generation is made of 142 blue and 58 red marbles. Fourth generation R R R H D H H R D R H R R R H H H R H D H R R R R R H R R H R H R R H R D H R R H R H H H H R H R R H H R D R R R R R R H H R H H D H H H R R H R R H H R R H H D H H D H D R H H H H R D R H R H R H H q3 = 0.708 Genotypes D H R Total Observed frequencies 10 40 50 100 Adaptive values 0.5 0.5 1 Frequencies after selection 5 20 50 60 q4 = (10 + 50)/60 = 0.8 q = q4 - q3 = 0.8 - 0.708. = 0.092 Next we compare the observed results with the theoretical values. For the theoretical values of q use the formula q1 = q(1-sp)/(1-sp(1+q)). The formula for q is the same as given in section on theory. q = spq^2/(1-sp(1+q)), or simply take q = the difference between the values of q in two consecutive generations. Remember that each generation is calculated from the values of the previous generation. For instance, q2 = q1(1-sq1) and so on. For more about the theoretical values see the section: Main Menu/Natural Selection Theoretical values of q and q. Observed values of q and q. qo = 0.5 q qo = 0.5 q q1 = 0.6 0.1 q1 = 0.567 0.067 q2 = 0.706 0.106 q2 = 0.637 0.070 q3 = 0.804 0.098 q3 = 0.708 0.071 q4 = 0.881 0.077 q4 = 0.8 0.092 The observed and the theoretical values of q and of q correspond fairly well as shown by the graphs. To see the graphs click on the button below labeled Graphs. The significance of the selection Model 3. Dominant mutatins are rarer than reces- sive ones. While the recessive genes can be harbored in the heterozygous condition, the same cannot be said of dominant mutations. Since most of the dominant mutations are harmful, many of them are found at mutation levels. Some dominant mutants are lethal when homozygous. (The CPDS stock in Drosophila genetics is an example.) Since selection involves both, the homozygous dominants and the heterozygotes, the gene frequency p is decreasing quite rapidly, and q is increasing. The erosion of harmful mutants is a form of normalizing selection. End of section.*CARDD(n ? Sub Menuon mouseUp set scroll of card field 1 to 0 go to Card 47 end mouseUpn p? Main Menuon mouseUp set scroll of card field 1 to 0 go to Card 2 end mouseUp< ??Selection against a2 allele"Jb Lw? Graphson mouseUp go to Card 61 end mouseUp(ˀB . ? 1&o&(z Model 4. Selection against the a2 allele when heterozygote is at midpoint in adaptive value between the homozygotes. Theory. qo = 0.50. Adaptive values of H is 0.75 and of R is 0.5. Genotypes D H R Total Observed frequencies p^2 2pq q^2 1 Adaptive values 1 1-s 1-2s Frequencies after selection p^2 2pq(1-s) q^2(1-2s) 1-2sq q1 = (q-sq(1+q)/(1-2sq) q = -spq/(1-2sq) First generation: H H H D D H D D H H H D R D D R H H H R D H H H H D H H H R R H H H D H H H D R D D H H H H H H D R R D D D D H H D D H H H D R H H D R H R H H H R H R H H H H R D H H H H H R H H H R D H R D H H H R qo = 0.50 Genotypes D H R Total Observed frequencies 25 57 18 100 Adaptive values 1 0.75 0.5 Frequencies after selection 25 43 9 77 q1 = (21.5 + 9)/77 = 0.396 q = q1 - qo = 0.396 - 0.5 = -0.104 The next generation is made of 79 blue and 121 red marbles. Second generation H H H H H D H R D D H D H H D H D H R D H H H R R R D R R H D D H H D H H H H R D D H D D H D R D D H D D R D R H H R H H H H H H D R H D H D H D H D H H D D H H R H H D H D H H D H D D H D D H D D H q1 = 0.396 Genotypes D H R Total Observed frequencies 37 49 14 100 Adaptive values 1 0.75 0.5 Frequencies after selection 37 37 7 81 q2 = (18.5 + 7)/81 = 0.315 q = q2 - q1 = 0.315 - 0.396 = -0.081 The next generation is made of 63 blue and 137 red marbles. Third generation D H D D D R R D D D D H D D H H H D H H D D H D D H D D H D H R D H D R H R D D H R D H D D H D H H H D D D H H H H D H D D H R D D H D R H D D R D D D H D D D D H H H H D H D R D H H D H H D R D H H q2 = 0.315 Genotypes D H R Total Observed frequencies 50 40 10 100 Adaptive values 1 0.75 0.5 Frequencies after selection 50 30 5 85 q3 = (15 + 5)/85 = 0.235 q = q3 - q2 = 0.235 - 0.315 = -0.08 The next generation is made of 47 blue and 153 red marbles. Fourth generation H H H D D D D D D D H D H D H D D H H D D D H D H D D D D D D D D D D D H D R D D H D H D D D D D H H D H D H D H D D H H H D H H H D D D D H D H R D D D H D D H H H D D H D D D H D D D H D R D D D H q3 = 0.235 Genotypes D H R Total Observed frequencies 63 34 3 100 Adaptive values 1 0.75 0.5 Frequencies after selection 63 25.5 1.5 90 q4 = (12.75 + 1.5)/90 = 0.158 q = q4 - q3 = 0.158 - 0.235 = -0.077 Next we compare the observed results with the theoretical values. For the theoretical values of q use the formula q1 = (q - sq(1+q))/(1-2sq). The formula for q is the same as given in the section on theory. q = -spq/(1-2sq), or simply take q as the difference between the values of q in two consecutive generations. Remember that each generation is calcul- ated from the values of the previous generation. For instance, q2 = q1(1-sq1) and so on. For more about the theoretical values see the section: Main Menu/Natural selection Theoretical values of q and q. Observed values of q and q. qo = 0.5 q qo = 0.5 q q1 = 0.396 -0.104 q1 = 0.417 -0.083 q2 = 0.315 -0.081 q2 = 0.333 -0.084 q3 = 0.235 -0.08 q3 = 0.266 -0.067 q4 = 0.158 -0.077 q4 = 0.209 -0.057 The observed and the theoretical values of q and of q correspond fairly well as shown by the graphs. To see the graphs click on the button below labeled Graphs. The significance of the selection Model 4. In this model there is no dominance, which means that the heterozygotes are different in phenotype from both homozygotes and can become subjects of natural selection in their own ways. The a2 allele is not protected in the heterozygotes by dominance. As a result, selection becomes more effective and the resulting changes are brought about faster. The model represents the additive gene effect, and as such it is suitable to be extended to more complex polygenic systems. End of section.3 CARDE1Xn ? Sub Menuon mouseUp set scroll of card field 1 to 0 go to Card 47 end mouseUpn p? Main Menuon mouseUp set scroll of card field 1 to 0 go to Card 2 end mouseUp8 ?Ԁ?Selection in favor of H"Jb Lw? Graphson mouseUp go to Card 62 end mouseUp1SZGU\    #!!..-0 Model 5. Selection favoring the heterozygote. Theory. qo = 0.50. Adaptive value of both D and R is 0.5, (s1=s2) Genotypes D H R Total Observed frequencies p^2 2pq q^2 1 Adaptive values 1-s1 1 1-s2 Frequencies after selection p^2(1-s1) 2pq q^2(1-s2) 1-s1p^2-s2q^2 q1 = (q-s2q^2)/(1-s1p^2-s2q^2) q = pq(s1p - s2q)/(1-s1p^2-s2q^2) First generation: H H H H H R D H D H H R D H H H H D D H H D D H H D R H H D H H R R D D D D D H D H H D D H D H H D D H H D D R R D H H H H D H H H D D R D H H H H H H D H H H R H D R R R H H R D D R H D H D H H D D qo = 0.50 Genotypes D H R Total Observed frequencies 34 52 14 100 Adaptive values 0.5 1 0.5 Frequencies after selection 17 52 7 76 q1 = (26 + 7)/76 = 0.434 q = q1 - qo = 0.434 - 0.5 = -0.066 The next generation is made of 87 blue and 113 red marbles. Second generation: D H D R H R D R R R H R D D D R D R D H D R H H D D D D H R H D H D H D H H R H H D D D H D D H H D D H H D D H H H R D H D D R H D H D H H R D R H D H H R R R R H H D H D R D D H R R D D H D H R H D q1 = 0.434 Genotypes D H R Total Observed frequencies 39 38 23 100 Adaptive values 0.5 1 0.5 Frequencies after selection 19.5 38 11.5 69 q2 = (19 + 11.5)/69 = 0.442 q = q2 - q1 = 0.442 - 0.434 = 0.008 The next generation is made of 89 blue and 111 red marbles. Third generation: H D H R D D D H H H H H H H D D R H D H H D D H R H H R D R D D D D H R D D D D R H D H H H D H D D D H D R H H D H R H H H H H D H H H H D H R R R D R D H D D H R D D D H H H R R H D D H H H H R D R q2 = 0.442 Genotypes D H R Total Observed frequencies 37 45 18 100 Adaptive values 0.5 1 0.5 Frequencies after selection 18.5 45 9 72.5 q3 = (22.5 + 9)/72.5 = 0.434 q = q3 - q2 = 0.434 - 0.442 = -0.008 The next generation is made of 87 blue and 113 red marbles. Fourth generation H H R D D H D H H D R H D H D R H H H D D H D D H H H R H D R R D H H H H H H H D H R D H R H D R R H H D R D H H H R D D H D R H H H H H H H H D H D H R D D D H R H D H H H H D D H H D D H H H H H H q3 = 0.434 Genotypes D H R Total Observed frequencies 29 55 16 100 Adaptive values 0.5 1 0.5 Frequencies after selection 14.5 52 8 74.5 q4 = (26 + 8)/74.5 = 0.456 q = q4 - q3 = 0.456 - 0.434 = 0.022 The next generation is made of 91 blue and 109 red marbles. Fifth generation: R R R H R D D H R D D R H H R H D H H H R H D H H H H H R R H D R H H R R H H R H H H D D R H H R H R H H H D H R D H H D D H R H H D R D H H H H R D H H R D D D D H H D D D H H D R D H D H D H R R H q4 = 0.456 Genotypes D H R Total Observed frequencies 26 49 25 100 Adaptive values 0.5 1 0.5 Frequencies after selection 13 49 12.5 74.5 q5 = (24.5 + 12.5)/74.5 = 0.497 q = q5 - q4 = 0.497 - 0.456 = 0.041 Next we compare the theoretical values of q and q with the observed values and construct two graphs, one for q and one for q. For the theoretical values of q use the formula q1 = (q-s2q^2)/(1-s1p^2-s2q^2). The formula for q is the same as given in section on theory. q = pq(s1p-s2q)/(1-s1p^2-s2q^2), or simply take q as the difference between the values of q in two consecutive generations. For these theoretical values of q ands q see Main Menu/Natural Selection. To see the graphs, click on the Graphs button below. The graphs show that q is approaching the equilibrium value which is in this case 0.5. Theoretical values of q and q. Observed values of q and q. qo = 0.5 q qo = 0.50 q q1 = 0.5 0 q1 = 0.434 -0.066 q2 = 0.5 0 q2 = 0.442 0.008 q3 = 0.5 0 q3 = 0.434 -0.008 q4 = 0.5 0 q4 = 0.456 0.022 q5 = 0.5 0 q5 = 0.497 0.041 The significance of selection Model 5. Selection favoring the heterozygotes assures that both alleles remain in the population at a high value in a stable equilibrium. The point of equilibrium depends on the strengths of the selection coefficiens. In this example, since the selection coefficients are equal, the equilibrium point is at q = 0.5. For this reason, this type of selection is called balancing selection. An actual example would be sickle cell anemia. In places where malaria is endemic, the two homozygotes are selected against either by malaria or by anemia. The heterozygotes, however, are neither anemic, nor do they suffer from malaria. Heterozygous superiority is a fairly common feature in natural populations. End of section.+CARDF&~*n ? Sub Menuon mouseUp set scroll of card field 1 to 0 go to Card 47 end mouseUpn p? Main Menuon mouseUp set scroll of card field 1 to 0 go to Card 2 end mouseUp4 ??Selection against H"Jb Lw? Graphson mouseUp go to Card 63 end mouseUp*BGV]o  _o&') Model 6. Selection against the heterozygote. Theory. qo = 0.50. Adaptive value of H is 0.5 and of R and D is 1. Genotypes D H R Total Observed frequencies p^2 2pq q^2 1 Adaptive values 1 1-s 1 Frequencies after selection p^2 2pq(1-s) q^2 1-2spq q1 = (q-spq)/(1-2spq) q = spq(2q - 1)/(1-2spq) First generation: H R H R D R R D R D H H H R H H H D H H H H H H H H D H D R H R H H D D H H R R H D D H H H H H H R H D D H D H H R D H R H D D D H H H H H D D H D R H H H H R H D R H D D H D H R H R R R H D R H D R qo = 0.50 Genotypes D H R Total Observed frequencies 26 52 22 100 Adaptive values 1 0.5 1 Frequencies after selection 26 26 22 74 q1 = (13 + 22)/74 = 0.473 q = q1 - qo = 0.473 - 0.5 = -0.027 The next generation is made of 95 blue and 105 red marbles. Second generation: R R H D R D D R D R D H H D H H D R D D H H H R H D R H H H H D H D H D H R H R R D H R H D R H R H D D H R H R H H R R D D D D D R D D D H H D H H H R H D H H R H H D R R D R D H D R H D H H H R H H q1 = 0.473 Genotypes D H R Total Observed frequencies 31 43 26 100 Adaptive values 1 0.5 1 Frequencies after selection 31 21.5 26 78.5 q2 = (10.75 + 26)/78.5 = 0.468 q = q2 - q1 = 0.473 - 0.5 = -0.005 The next generation is made of 94 blue and 106 red marbles. Third generation D H D D R H H H D H D H R H H H H R R R D D R D H H H R H R D H H H D R D H D R H R H H H D H D H H H H D D H H H H R H R H D H R H H D H D H H R D D H H D H R R D D H D D R R D H H R R D D R H H H D q2 = 0.468 Genotypes D H R Total Observed frequencies 30 48 22 100 Adaptive values 1 0.5 1 Frequencies after selection 30 24 22 76 q3 = (12 + 22)/76 = 0.316 q = q3 - q2 = 0.316 - 0.468 = -0.152 The next generation is made of 63 blue and 137 red marbles. Fourth generation D D R H D R H D D D D D H R D D H D D H H H H D H D D D D D H R D H H R D D R D R D H R H D D R H H D H D H D D H D D H D H R D D D D D H D D D H D D D H D D R R D D H H H D D D D D D D D H R D H D D q3 = 0.316 Genotypes D H R Total Observed frequencies 58 29 13 100 Adaptive values 1 0.5 1 Frequencies after selection 58 14.5 13 85.5 q4 = (7.25 + 13)/85.5 = 0.237 q = q4 - q3 = 0.237 - 0.316 = -0.079 Next we compare the observed results with the theoretical values. For the theoretical values of q use the formula q1 = (q-spq)/(1-2spq). The formula for q is the same as given in section on theory. q = spq(2q - 1)/(1-2spq), or simply take q as the difference between the values of q in two consecutive generations. Remember that each generation is calculated from the values of the previous generation. For instance, q2 = q1(1-sq1) and so on. For more about the theoretical values see the section: Main Menu/Natural Selection. Theoretical values of q and q. Observed values of q and q. qo = 0.5 q qo = 0.5 q q1 = 0.5 0.0 q1 = 0.473 0.027 q2 = 0.5 0.0 etc. q2 = 0.468 0.005 in unstable equililbrium q3 = 0.316 0.152 q4 = 0.237 0.079 The differences between the observed and the theoretical values of q and of q are due to random factors of sampling. The equilibrium at q = 0.5 is not stable. The moment the gene frequencies move from the equilibrium value they have the tendency to run to 0 or to 1, as shown by the observed data. To see the graphs click on the button below labeled Graphs. The significance of the selection Model 4. Selection against the heterozygote is also called disruptive selection. Heterozygotes are produced by mating between the two homozygotes. If the heterozygous offspring has reduced viability, the population will be eventually split into two reproductively isolated populations. Model 4 provides a genetic mechanism of speciation. In the human situation Rh incompatibility is an example of selection against the heterozygote. If the incompatibility were absolute, this mechanism would split the human race into two distinct, reproductively isolated species. Fortunately, the incompatibility is only partial, and it can be further lessened by medical intervention. End of section.CARDG.M9x ? Sub Menuon mouseUp set scroll of card field 1 of card 52 to 0 go to Card 47 end mouseUpx p? Main Menuon mouseUp set scroll of card field 1 of card 52 to 0 go to Card 2 end mouseUp> =?Complete selection against RRw? 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Back to Texton mouseUp go to Card 57 end mouseUp BMAPRUNAKl`!~0 @K0@;$0|;B0;B0KB0KB.0 BKB.P~####5f@Ec.#!@$@#####$(####$)$)>@@J0@`Jx"0J"`""z@`@J@JxJ0 $@3`>3`>.1~@zJ` ?@0 J".Y3",",?@0F@|Y3 18J? $@>a 8x(l$`'}'p>>$`##J0@8Jx@|J@`)` "" ""0J$@(@3@0DK3 $ #$@F $ 0PK<0##3$@#@#@3@>@@ J` ?@` JY3,"?@`@Y3  EQ$@0;!>@0J0@xJx@`J||@`J@xJx $@00;0-@#$##$#@$ @) ## #`)0` `#0 `#@`03-(@8#`$`-0(#0#$###8'ρ18$A!1!8$B!) 6'ρ19??iq" >'""YaK hq" >< WahC2??I 9d!!#!9'H!!}$@3lc)N8}$@8b|l#@(#Pzc)N9l@  8bQ2 QD{Q"$QE'#P8bXk@  |Q"$QE|!N=+ I| k1c+ \9| \Sk1cM\ |1@p!\SkM|2H")|,c!ƀFREEFree Object 23n ? Sub Menuon mouseUp set scroll of card field 1 to 0 go to Card 43 end mouseUpn p? Main Menuon mouseUp set scroll of card field 1 to 0 go to Card 2 end mouseUp4 ??Variation in Beans"Jl 3 { G ^   *!?    !6!J!!$5$T((**.T.[2`The purpose of the experiment is to become familiar with handling the mathematics of variation. This is achieved by measuring the amount of phenotypic variation in three samples of beans. If it can be shown that the variation between samples (or between individuals) is greater than the within sample variation, we have established the presence of a situation in which natural selection can be effective, provided some of the phenotypic variation is due to genetic causes. This is a simple exercise in the study of phenotypic variation. The amount of genetic effect which contributes to this variation is not investigated here. Materials and methods. In this experiment we measure the weights of three types of beans, 100 in each of three samples. The beans were Lima beans, Kidney beans, and Black- eyed peas. It is convenient to use an electronic balance with digital read-out in grams to three decimal places. First, the balance should be zeroed out. Then each bean is weighed and the weight is recorded rounding off the third digit to two figures after the decimal point. Before you begin measuring the beans, select one hundred at random from a given type. Put the beans on the table and do not hold them in your hand. It is a good idea to remove the beans from the balance by the use of a brush or a strip of paper. Instead of picking them up by hand, simply push the beans off the pan of the balance. It takes about 20 minutes to measure 100 beans. The raw data from an actual experiment are tabulated below. Data: 100 KIDNEY BEANS (Weights in grams.) x = 54.90 g 0.63 0.82 0.59 0.72 0.60 0.54 0.60 0.62 0.41 0.59 0.58 0.63 0.62 0.53 0.46 0.66 0.39 0.57 0.54 0.44 0.40 0.43 0.67 0.46 0.48 0.63 0.63 0.50 0.57 0.51 0.47 0.60 0.57 0.55 0.56 0.47 0.62 0.50 0.50 0.59 0.55 0.58 0.68 0.43 0.61 0.49 0.60 0.55 0.69 0.69 0.53 0.51 0.42 0.72 0.48 0.37 0.57 0.58 0.52 0.38 0.49 0.64 0.49 0.55 0.67 0.49 0.66 0.38 0.51 0.43 0.47 0.42 0.42 0.53 0.59 0.47 0.52 0.65 0.42 0.58 0.71 0.50 0.59 0.64 0.53 0.35 0.51 0.50 0.52 0.54 0.75 0.63 0.57 0.63 0.59 0.53 0.45 0.61 0.54 0.70 100 LIMA BEANS (Weights in gram) y = 92.82 g 1.39 1.17 0.75 0.86 1.25 1.24 1.07 0.61 1.22 0.94 0.90 0.81 1.08 0.78 0.87 1.18 0.89 1.02 0.95 0.95 0.79 0.71 0.83 0.72 0.81 1.07 1.06 0.80 1.07 0.74 1.12 0.66 0.70 1.02 1.13 0.76 0.98 1.14 0.68 0.92 0.93 0.90 0.80 0.52 1.00 1.08 1.16 0.82 1.07 1.03 1.09 1.00 1.24 0.90 0.81 0.92 0.96 0.73 1.08 1.00 0.70 0.85 0.93 0.81 0.58 0.92 0.71 1.01 0.93 0.77 0.78 0.89 0.78 0.97 1.04 1.20 1.02 0.89 0.59 0.91 1.18 0.84 0.95 1.10 1.09 0.65 0.96 1.18 0.73 1.04 0.79 0.62 0.49 1.09 1.28 0.89 0.94 1.00 0.97 1.04 100 BLACK-EYED PEAS (Weights in grams) z = 22.75 g 0.21 0.10 0.13 0.17 0.26 0.12 0.24 0.21 0.17 0.30 0.17 0.24 0.29 0.20 0.25 0.21 0.23 0.27 0.22 0.25 0.21 0.33 0.27 0.13 0.29 0.13 0.25 0.24 0.20 0.28 0.20 0.16 0.26 0.33 0.27 0.25 0.30 0.23 0.20 0.29 0.20 0.26 0.21 0.22 0.23 0.29 0.20 0.19 0.22 0.23 0.27 0.26 0.30 0.18 0.24 0.24 0.27 0.25 0.18 0.25 0.26 0.14 0.25 0.20 0.17 0.12 0.24 0.17 0.25 0.18 0.26 0.19 0.31 0.16 0.18 0.17 0.35 0.31 0.34 0.28 0.18 0.21 0.26 0.24 0.26 0.26 0.23 0.19 0.12 0.22 0.16 0.24 0.22 0.23 0.23 0.21 0.22 0.19 0.24 0.27 Next, I squared each entry and calculate the sum of the squared items in each sample. I arranged the individual entries according to magnitude and frequency to avoid the repeated squaring of the same numbers. KIDNEY BEANS: x2 = 30.712 0.123 0.137 0.289 (0.144 x 2) 0.152 0.168 0.353 (0.176 x 4) 0.555 (0.185 x 3) 0.194 0.203 0.423 (0.212 x 2) 0.884 (0.221 x 4) 0.461 (0.230 x 2) 0.960 (0.240 x 4) 0.160 1.040 (0.260 x 4) 0.811 (0.270 x 3) 1.405 (0.281 x 5) 1.166 (0.292 x 4) 1.210 (0.302 x 4) 0.314 1.625 (0.325 x 5) 1.346 (0.336 x 4) 2.089 (0.348 x 6) 1.250 (0.250 x 5) 0.744 (0.372 x 2) 1.922 (0.384 x 5) 1.588 (0.397 x 4) 0.819 (0.410 x 2) 0.423 0.872 (0.436 x 2) 0.898 (0.449 x 2) 0.462 0.952 (0.476 x 2) 1.440 (0.360 x 4) 0.504 1.037 (0.518 x 2) 0.563 0.490 0.672 LIMA BEANS. y2 = 89.413 0.240 0.270 0.336 0.348 0.372 0.384 0.423 0.436 0.462 0.980 (0.490 x 2) 1.008 (0.504 x 2) 1.066 (0.533 x 2) 0.598 0.563 0.578 0.593 1.217 (0.608 x 2) 1.872 (0.624 x 2) 1.280 (0.640 x 2) 2.624 (0.656 x 4) 0.672 0.689 0.706 0.723 0.749 3.961 (0.792 x 5) 2.430 (0.810 x 3) 0.828 2.539 (0.846 x 3) 2.595 (0.865 x 3) 1.767 (0.884 x 2) 2.708 (0.903 x 3) 1.843 (0.922 x 2) 1.882 (0.941 x 2) 0.960 4.000 (1.000 x 4) 1.020 3.121 (0.040 x 3) 1.061 3.245 (1.082 x 3) 1.124 4.580 (1.145 x 4) 3.499 (1.166 x 3) 3.564 (1.188 x 3) 1.210 1.254 1.277 1.300 1.346 1.369 4.177 (1.392 x 3) 1.440 1.488 3.075 (1.538 x 2) 1.563 1.638 1.932 BLACK-EYED PEAS. z2 = 5.476 0.010 0.043 (0.014 x 3) 0.051 (0.017 x 3) 0.020 0.077 (0.026 x 3) 0.073 (0.029 x 6) 0.162 (0.032 x 5) 0.144 (0.036 x 4) 0.240 (0.040 x 6) 0.309 (0.044 x 7) 0.288 (0.048 x 6) 0.370 (0.053 x 7) 0.518 (0.058 x 9) 0.504 (0.063 x 8) 0.608 (0.068 x 9) 0.437 (0.073 x 6) 0.157 (0.078 x 2) 0.421 (0.084 x 5) 0.270 (0.090 x 3) 0.192 (0.096 x 2) 0.218 (0.109 x 2) 0.116 0.123 Finally, I obtained the between and the within sample variance estimates as the ratios of the corresponding sum of squares and degrees of freedom. I obtained a calculated F number as the ratio of the greater and the lesser variance estimates. Then I compared this F number with the corresponding value in the F table. As a rule, If the calculated value is less than the one in the table at 0.05 probability than the difference between the between and within samples variations is not significant. Otherwise, it may be significant or highly significant. (To check up on statistical concepts and procedures select Sub Menu / Analysis of Variance. To see the F Tables, select Sub Menu / F Tables.) Finally, I performed the following calculations: Correction Factor (CF) = Grand total squared (T2)/N where N is the total number of items in all samples, i.e. 300. T = 170.47 g, and T2 = 29060.02.. CF = 86.867 Total sum of squares = total of squared items - CF = 125.601 - 86.867 = 28.73. Total degrees of freedom = 299. Between samples sum of squares = sum of the squared sample totals divided by 100 (the number of items in each sample) - CF = 517.563 + 8615.552 + 3014.010 = 12147.125 12147.125/100 = 121.471 and 121.471 - CF = 24.604. The between samples degrees of freedom is one less than the number of samples = 2. The within samples sum of squares and the within samples degrees of freedom is the difference between the total and the between samples sum of squares and degrees of freedom. Thus: 4.126 and 297 respectively. Putting all these calculations together, I obtained the following table of analysis of variance: TABLE OF ANALYSIS OF VARIATION. _________________________________________________ Sources of Sum of Degrees of Variance variation squares freedom estimate _________________________________________________ Total 28.730 299 - _________________________________________________ Between 24.604 2 12.302 samples _________________________________________________ Within 4.126 297 0.014 samples _________________________________________________ The calculated F number is the ratio of the greater and lesser variance estimates = 12.302/0.014 = 878.714. The corresponding numbers in the F table are 3.23 and 5.18 at 0.05 and 0.01 probabilities respectively. It follows that the difference between the two variations is highly significant. (To see the F table, select Sub Menu / F Table.) Conclusion. Beans are agricultural products and as such they must be maintained at an ex- pected quality for marketing. As a result, the within samples variation is kept at minimum while the between samples variation is large. This large variation is an expression of the natural genetic richness of the genus and has its source in the evolution process. Human intervention enhances and maintains the already given natural diversity. Further considerations.. I was wandering, how accurate are the measurements using the electronic balance. To test accuracy, I first measured the same bean ten times in the same way as I did in the experiment by rounding off the digit at the third decimal place. The se- lected bean was a medium sized Lima bean. All ten measurements were the same at 0.96 g. Next I measured the same bean, again ten times, without rounding off the third digit. The following set of measurements were obtained: 0.963 0.957 0.959 0.957 0.959 0.963 0.960 0.960 0.964 0.965 In this last set of repeated measurements the third digit seems to float freely. Nonetheless, it became clear that by using the rounding off process these seemingly random fluctuations of the third digit are most effectively eliminated resulting in a set of well repeatable and accurate measurements. Finally, I investigated the nature of the random fluctuations of the third digit by first closing the lid of the balance to eliminate all movements of the air, and then zeroing out the balance. For the balance I was using, a star on the digital readout panel showed that the balance was zeroed out. When this star appeared the readout was 0.000 and it did not disappear all through the observation, which lasted 2 minutes. The third zero after the decimal point, however, changed approximately eight times per minute giving the following sequence of values: 0, -1, 0, +1, 2, 3, 4, 5, 6, 7, 6, 5, 4, 3, 4, 5, 6, 7, 6, 5, 4, 3, 2, 1, 0, -1, -3, -4, -3, -2, -3, -4. The nature of the drifting seemed to be random and the range remained within one hundredth of a gram. Consequently, the .rounding off method used in the experiment effectively neutralizes this random effect. In conclusion, the data in the experiment may be considered as satisfactorily accurate. End of section.v CARDTtn ? Sub Menuon mouseUp set scroll of card field 1 to 0 go to Card 43 end mouseUpn p? Main Menuon mouseUp set scroll of card field 1 to 0 go to Card 2 end mouseUp. ??Draw a Circle"J{ Ns? Figure 1on mouseUp go to Card 68 end mouseUpTr? SampleSummaryon mouseUp go to card 222 end mouseUpt     % + , z  q %:"@Fc'  7 = X _ {     !A%B%^%f%%%& &b*a*|****+&+[.../34555566889E9d>>@AJKaPOPUVZ[Z\F\M\\`` `b`d``ddj<jAr= Materials and methods. Each data entry is a circle drawn on an 8 1/2" x 11 " piece of white paper, held in the portrait position. At least ten to twelve willing individuals are selected for this experiment. Each is asked to draw a circle on the paper on ten different occasions, let us say on every other day. It will take over three weeks to collect all the data. Some people may feel creative, others may want to break the monotony and will draw large and small circles in many different places within the area of the paper. Consequently, the areas of the circles or the points of origins (where the pen or pencil first touches the paper) may be too much under conscious control and may not suitable to measure a spontaneous, within sample variation. The participants should be asked, therefore, to close their eyes prior to drawing and make their minds blank. Then opening their eyes look at the paper and fraw whatever comes immediately without much conscious reflection. Once all the data have beena collected the method of analysis of variance is applied to the sets of data. (See Sub Menu / Analysis of Variance.) It should be noted that this exercise simnply provides the materials for a study of variation and is meant to be a means to acquire the skills of analysis of variance. For any variation to be meaningful in terms of genetics and evolution, there must be variation between individuals and that variation must have a genetic component. Here we simply study phenotypic variation for the sake of exercise. The variants in this study are the Draw a Circle exercise are the points of origin of the circles and the areas of the circles in cm^2. The point of origin of a circle is determined as an (x, y) pair of numbers as distances in centimeters measured from the left margin of the paper (the x value) and from the bottom of the patper (the y value). As to the areas of the circles there is a relatively precise way to mesure them. Make a Xeroxed copu of the original circle on teh 8 1/2 x 11 inch paper and cut it out from the copy with scissors as accurately as you can. Then weigh the cut out circle on an analytical balance and using the weight of a known area of the same paper calculate the weights in square centimeters. A somewhat simplified method would be to mesure the vertical and the horizontal diagonals of each circle and take the average of the two measurements. Dividing this by two an estimated radius of the circle is given. From this the area may be calculated in square centimeters as 3.14 x r^2. Click the Figure 1 button below to see an examples of data sheets for the Draw a Circle exercises. PART I: ANALYSIS OF VARIATION IN AREAS (WEIGHTS IN g) OF CIRCLES. Here is a completed study of variation in the Draw a Circle exercise. There were 20 people in this study, and each contributed 10 drawings. This means that the total number of data is N = 200, the number of samples is 20, and each sample has n = 10 entries. The data are given below. The first two numbers are the (x, y) values in centimeters. The third figure is the weight of the cut out circles in gramms. Anthony, Thomas Apa, Michael Archibold, Smitha x y g g^2 x y g g^2 x y g g^2 15.7 17.2 1.444 2.09 13.2 19.3 0.487 0.24 7.5 18.2 0.508 0.26 16.9 17.6 1.280 1.64 11.3 19.0 0.554 0.31 8.7 18.7 0.316 0.10 16.6 17.2 1.211 1.47 12.9 20.7 0.577 0.33 9.1 18.5 0.559 0.31 15.6 14.4 1.177 1.39 13.3 19.5 0.600 0.36 8.3 19.5 0.720 0.52 15.7 17.7 1.111 1.23 14.2 20.7 0.753 0.57 9.1 18.4 0.631 0.40 16.7 20.5 1.144 1.31 14.1 20.7 0.815 0.66 8.1 19.4 0.384 0.15 15.4 17.8 1.280 1.64 12.1 20.7 0.700 0.49 7.5 19.2 1.289 1.66 13.1 18.3 1.461 2.13 13.5 20.5 0.720 0.52 11.3 19.7 1.135 1.29 14.0 18.9 1.177 1.39 14.1 20.8 0.662 0.44 9.4 19.6 0.231 0.05 16.5 18.3 1.046 1.09 13.5 18.9 0.503 0.25 9.8 19.6 0.637 0.41 156.2 177.9 12.331 15.38 132.2 200.8 6.371 4.17 88.8 190.8 6.410 5.15 Ash, Trinitia Buchakjian, Michael Burnell, Maura x y g g^2 x y g g^2 x y g g^2 11.7 21.9 0.508 0.26 10.2 18.5 0.497 0.24 9.3 17.7 0.439 0.19 11.6 20.1 0.315 0.10 11.0 17.8 0.727 0.53 6.6 18.6 0.333 0.11 12.3 19.3 0.414 0.17 10.2 17.2 0.503 0.25 10.7 18.7 0.508 0.23 11.2 20.1 0.389 0.15 9.8 16.5 0.694 0.48 8.6 18.6 0.429 0.18 12.1 19.5 0.465 0.22 10.0 18.2 0.583 0.34 10.0 19.3 0.656 0.43 10.5 19.9 0.769 0.59 10.6 18.3 0.601 0.36 6.5 16.8 0.619 0.38 12.3 21.1 0.774 0.60 10.3 16.6 0.553 0.31 8.9 19.7 0.370 0.14 13.6 20.6 1.095 0.20 9.2 18.3 0.548 0.30 9.9 18.8 0.449 0.20 12.0 20.2 0.368 0.14 10.1 18.2 0.681 0.46 8.1 18.4 0.460 0.21 13.5 20.6 0.643 0.41 10.7 18.5 0.465 0.22 9.2 20.5 0.681 0.46 120.8 203.3 5.740 3.84 102.1 178.1 5.852 3.49 87.8 187.1 4.954 2.53 Carr, Brian Cunningham, Danielle Dougan, Molly x y g g^2 x y g g^2 x y g g^2 9.3 18.9 0.662 0.44 10.9 18.7 0.333 0.11 9.6 20.2 0.508 0.26 9.0 17.4 0.631 0.40 10.4 19.5 0.231 0.05 11.1 20.2 0.465 0.22 9.2 18.7 0.740 0.55 10.0 18.2 0.286 0.08 9.2 19.8 0.727 0.53 9.3 17.7 0.399 0.16 9.8 18.7 0.294 0.09 10.1 20.5 0.531 0.28 9.7 17.5 0.286 0.08 10.4 18.3 0.282 0.08 10.8 20.5 0.553 0.31 9.1 17.1 0.298 0.09 10.4 18.5 0.202 0.04 9.2 19.1 0.465 0.22 9.7 17.6 0.324 0.10 9.8 19.3 0.294 0.09 9.2 19.0 0.794 0.63 9.2 18.2 0.514 0.26 10.4 17.8 0.231 0.09 9.7 20.5 0.650 0.42 9.8 18.5 0.548 0.30 11.8 18.3 0.307 0.09 10.9 20.5 0.858 0.74 9.5 19.6 0.531 0.28 10.3 19.3 0.356 0.13 9.4 19.5 0.389 0.15 93.8 181.2 4.933 2.66 104.2 187.6 2.916 0.86 99.2 199.8 5.940 3.76 Doyle, Lisa Endres, Tracy Grenga, Jessica x y g g^2 x y g g^2 x y g g^2 12.3 20.0 0.747 0.56 11.8 17.8 0.455 0.21 14.4 19.9 0.643 0.41 12.0 20.5 0.311 0.10 12.1 18.7 0.351 0.12 12.7 21.0 0.854 0.73 11.8 20.5 0.316 0.10 15.2 17.6 0.429 0.18 14.2 25.0 0.727 0.53 12.7 20.5 0.938 0.88 12.7 16.5 0.449 0.20 14.0 19.0 0.857 0.73 11.0 19.3 0.519 0.27 12.0 18.0 0.380 0.14 13.2 20.5 0.784 0.61 10.0 19.5 0.669 0.45 12.2 17.8 0.380 0.14 14.2 19.6 1.143 1.31 11.0 20.3 0.449 0.20 14.0 18.9 0.707 0.50 13.5 23.0 0.953 0.91 11.5 19.0 0.306 0.09 13.5 17.4 0.961 0.92 12.5 22.0 0.707 0.50 11.5 20.0 0.822 0.68 13.5 18.7 0.320 0.10 13.6 19.3 0.707 0.50 12.6 19.4 0.699 0.49 13.4 16.7 0.455 0.21 13.7 22.0 0.753 0.57 116.4 199.0 5.773 3.82 130.5 178.1 4.887 2.72 136.0 211.3 8.128 6.80 Matthew, Ilardi Leo, Paul Olby, Aleisha x y g g^2 x y g g^2 x y g g^2 8.0 18.3 0.439 0.19 9.0 20.0 0.408 0.17 11.0 20.0 0.619 0.38 7.0 18.8 1.031 1.06 7.7 18.4 0.409 0.17 10.4 19.9 0.399 0.16 8.2 17.5 0.342 0.12 9.5 17.5 0.433 0.19 11.2 20.5 0.286 0.08 8.0 19.0 0.338 0.11 8.5 18.9 0.465 0.22 12.4 19.4 0.384 0.15 7.6 18.6 0.379 0.14 10.5 19.8 0.536 0.29 11.0 19.9 0.338 0.11 7.2 17.9 0.399 0.16 11.0 18.5 0.548 0.30 11.5 19.5 0.320 0.10 7.2 20.2 0.480 0.23 10.3 19.4 0.499 0.15 11.7 22.5 0.707 0.50 5.5 17.5 0.780 0.61 9.2 17.8 0.499 0.25 10.6 21.0 0.909 0.83 9.5 19.5 0.408 0.17 10.6 22.0 0.542 0.29 11.1 24.0 0.865 0.75 10.0 24.0 1.397 1.95 9.0 18.6 1.038 1.08 10.6 20.0 0.338 0.11 78.2 191.3 5.993 4.74 95.3 190.9 5.377 3.21 111.5 206.7 5.175 3.17 Paddock, Tracy Rohr, Jessica Szurek, Patrick x y g g^2 x y g g^2 x y g g^2 10.5 19.0 0.486 0.24 8.8 21.0 0.706 0.50 11.0 18.1 0.108 0.01 19.8 22.0 0.662 0.44 7.6 19.2 0.389 0.15 9.6 22.0 0.525 0.28 11.4 18.6 0.159 0.03 9.1 20.1 0.953 0.91 9.6 21.0 0.375 0.14 12.6 18.7 0.356 0.13 10.5 19.5 0.887 0.79 10.6 21.0 0.311 0.10 11.3 19.2 0.444 0.20 9.6 20.2 0.727 0.53 10.4 18.7 0.429 0.18 13.2 19.1 0.909 0.83 10.4 20.0 0.403 0.16 11.3 19.5 0.078 0.01 11.3 17.8 0.116 0.01 9.9 20.1 0.434 0.19 11.2 21.7 0.053 0.01 14.1 19.0 0.219 0.05 14.2 23.2 0.850 0.72 10.5 21.0 0.613 0.38 13.0 21.0 0.983 0.97 10.0 22.0 0.968 0.94 9.7 23.5 0.726 0.53 13.9 20.0 0.878 0.77 8.6 20.0 0.694 0.48 11.9 19.6 0.286 0.08 131.1 194.4 5.213 3.67 100.7 205.3 7.011 5.37 105.8 206.1 3.506 1.72 Zdep, Steven Szebenyi, Andrew x y g g^2 x y g g^2 The formula to change 11.4 17.5 0.298 0.09 13.7 21.0 0.909 0.83 weight to area is: 10.4 18.0 0.246 0.06 13.9 21.2 0.815 0.66 12.0 13.5 0.235 0.06 14.8 19.4 0.815 0.66 0.765 g = 100 cm^2 6.2 13.0 0.238 0.06 11.8 21.0 0.815 0.66 10.2 16.9 0.202 0.04 12.0 20.4 0.694 0.48 In practical terms, by divid- 10.0 18.0 0.459 0.21 11.5 19.9 0.794 0.63 ing the weights by 0.00765, 10.4 18.1 0.294 0.09 13.2 19.0 0.753 0.57 we get the areas of circles in 10.5 17.5 0.147 0.02 13.5 19.5 0.865 0.75 cm^2 10.4 18.0 0.133 0.02 13.6 19.4 0.649 0.42 11.4 18.0 0.150 0.02 12.1 20.0 0.700 0.49 102.9 168.5 2.202 0.67 129.9 200.8 7.809 6.15 The formula to change weight into erea was obtained by cutting out a piece of 10 cm x 10 cm, that is, 100 cm^2 piece of paper of the same kind as was used to collect the data, and weighing it on an analytical balance. The piece weighed 0.765 g. Note: It may be advisable to use the weight as coded data instead of the areas to avoid very large numbers. It should be remembered, however, if we code data by adding or subtracting the same number from each entry we will not effect variation, because variation is independent of origin. On the other hand, it we code data by multiplying or dividing each entry by the same numner we will change the overall variation. This cahnge will not effect the between and within samples variation relative to each another. To set up an ANOVA table we need the following. For each sample we need to calculate x, the column totals, x^2, the sum of the squared items, and (x)^2, the squared column totals; and from all the samples we need to calculate T, the grand total or sum of all column totals, and the correction factor CF = T^2/N where N is 200, the number of all entries in all the samples. x x^2 (x)^2 The correction factor CF = t^2/N = 719.31/100 = 3.597 12.33 15.38 152.03 Total sum of squares = (x^2) - CF = 83.88 - 3.597 6.37 4.17 40.58 Total sum of squares = 80.283 with 199 d.f. 6.41 5.15 41.09 Between samples sum of squares = ((x)^2/10) - CF 5.74 3.84 32.95 Between samples sum of squares = 72.74 with 19 d.f. 5.85 3.49 34.22 Within samples sum of squares = total - between ssq 4.95 2.53 24.50 Within samples sum of squares = 7.54 with 180 d.f. 4.93 2.66 24.31 2.92 0.86 8.53 5.94 3.76 35.28 5.77 3.82 33.29 4.89 2.72 23.91 8.13 6.80 66.10 5.99 4.74 35.88 5.38 3.21 28.94 5.18 3.17 26.83 5.21 3.67 27.14 7.01 5.37 49.14 3.51 1.72 12.32 2.20 0.67 4.84 7.81 6.15 61.00 26.82 83.88 763.44 TABLE OF ANALYSIS OF VARIATION. _________________________________________________ Sources of Sum of Degrees of Variance variation squares freedom estimate _________________________________________________ Total 80.283 199 - _________________________________________________ Between 72.74 19 3.828 samples _________________________________________________ Within 7.54 180 0.042 samples _________________________________________________ The calculated F number is the ratio of the greater and lesser variance estimates = 91.14 The corresponding numbers in the F table are 1.99 at 0.05 probability and 2.96 at 0.01 probability. Therefore, the difference between the two variations is highly significant in favor to the between sample variance. (To see the F table, select Sub Menu / F Table.) Conclusion. In this exercise we studied the variation in the performance of a behavior trait which may be under the influence of many factors, including some conscious control. Whatever be the source, the between samples variance was highly significantly greater than the within sample variance. It is the difference between the individuals in a population (the between sample variation in this case) which provides material for natural selection to work on. Of course, just from this result we cannot conclude that this particular range of differences in the size of drawn circles is of any actual selective significance. Still, the exercise is uselul to master the methematical technique of variation estimates. PART II: ANALYSIS OF VARIATION OF POINTS OF ORIGINS. The procedures of the analysis of variation of points or origin of circles are somewhat different from the previous analysis of areas (or weights) of circles. The areas are single values expressed in square centimeters, while points in a two dimensional space can only be described as (x,y) pairs of values in a coordinate system. I proceeded as described under Analysis of variance, Part II (Click on Sub Menu/Analysis of Variance, and then go down about two thirds of the section to Part II.) First I constructed the sample summaries. For each sample I plotted on a graph paper the ten points of origins of the circles, measured the corresponding (x, y) values in centimeters, and plotted the sample average as (x bar, y bar). I did this for each of the twenty samples. Finally I calculated the grand average and plotted it on each sample summary. Click on the button below called SampaleSummary to see the results of all this. Since variance estimate is the sum of squares divided by the number of degrees of freedom where the sum of squares is the sum of deviations from the mean squared, I could express these deviations as distances between the individual entries and the grand average and then square these distances. Going through all the sample summaries the following distances in centimeters were obtained. Anthony Apa Archibold Ash Buchakjian d d^2 d d^2 d d^2 d d^2 d d^2 6.6 43.56 0.4 0.16 0.4 0.16 1.2 1.44 2.2 4.84 2.3 5.29 2.5 6.25 1.4 1.96 1.0 1.00 1.3 1.69 5.1 26.01 2.1 4.41 1.8 3.24 2.9 8.41 1.6 2.56 5.9 34.81 2.3 5.29 2.3 5.29 2.7 7.29 1.5 2.25 4.9 24.01 3.4 11.56 3.0 9.00 1.2 1.44 0.9 0.81 4.6 21.16 3.3 10.89 3.6 12.96 0.8 0.64 1.1 1.21 6.1 37.21 3.4 11.56 2.5 6.25 1.0 1.00 2.3 5.29 5.5 30.25 2.8 7.84 3.8 14.44 2.2 4.84 3.1 9.61 2.9 8.41 2.2 4.84 2.2 4.84 2.8 7.84 2.8 7.84 5.7 32.49 1.7 2.89 2.3 5.29 0.9 0.81 1.5 2.25 49.6 263.20 24.1 56.69 23.3 63.43 16.7 34.71 18.3 38.25 Burnell Carr Cunningham Dougan Doyle d d^2 d d^2 d d^2 d d^2 d d^2 2.4 5.76 1.7 2.89 0.8 0.64 0.9 0.81 0.5 0.25 2.3 5.29 1.9 3.61 0.9 0.81 1.2 1.44 1.2 1.44 1.2 1.44 2.0 4.00 1.4 1.96 1.2 1.44 0.2 0.04 4.6 20.25 1.5 2.25 1.3 1.69 1.6 2.56 1.5 2.25 2.6 6.76 2.2 4.84 1.6 2.65 1.9 3.61 1.4 1.96 3.2 10.24 2.4 5.76 1.0 1.00 1.7 2.89 2.0 4.00 1.4 1.96 2.9 8.41 1.2 1.44 2.0 4.00 1.5 2.25 5.3 28.09 3.0 9.00 0.6 0.36 1.7 2.89 1.4 1.96 2.4 5.76 2.2 4.84 1.7 2.89 2.0 4.00 0.8 0.64 0.7 0.49 2.3 5.29 1.8 3.24 2.0 4.00 1.0 1.00 26.1 86.04 22.1 50.89 12.3 16.69 16.2 27.64 11.5 15.79 Endres Grenga Ilardi Leo Olby d d^2 d d^2 d d^2 d d^2 d d^2 1.6 2.56 3.0 9.00 4.9 24.01 2.7 7.29 0.9 0.81 3.2 10.24 2.5 6.25 1.6 2.56 0.8 0.64 1.0 1.00 1.9 3.61 3.1 9.61 4.0 16.00 2.2 4.84 1.8 3.24 1.5 2.25 3.4 11.56 3.1 9.61 0.9 0.81 0.6 0.36 3.4 11.56 2.4 5.76 4.1 16.81 2.7 7.29 0.8 0.64 3.0 9.00 2.3 5.29 3.6 12.96 3.6 12.96 1.2 1.44 1.1 1.21 3.7 13.69 5.9 34.81 2.3 5.29 4.7 22.09 4.4 19.36 4.4 19.36 3.2 10.24 2.5 6.25 3.3 10.89 2.4 5.76 6.5 42.25 4.2 17.64 2.4 5.76 0.5 0.25 2.9 8.41 3.0 9.00 3.5 12.25 0.8 0.64 1.3 1.69 25.4 73.96 34.3 131.77 38.1 156.88 20.9 51.77 16.1 42.41 Paddock Rohr Szurek Zdep Szebenyi d d^2 d d^2 d d^2 d d^2 d d^2 0.7 0.49 3.5 12.25 0.9 0.81 1.7 2.89 2.1 4.41 1.5 2.25 0.7 0.49 0.4 0.16 8.0 64.00 3.6 12.96 0.7 0.49 2.1 4.41 2.5 6.25 1.4 1.96 2.4 5.76 0.3 0.09 1.7 2.89 1.8 3.24 1.5 2.25 2.5 6.25 1.6 2.56 1.5 2.25 4.5 20.25 1.5 2.25 3.4 11.56 3.0 9.00 2.9 8.41 1.9 3.61 2.6 6.76 3.1 9.61 2.1 4.41 1.0 1.00 3.1 9.61 2.0 4.00 1.2 1.44 2.9 8.41 3.0 9.00 1.7 2.89 5.8 33.64 1.9 3.61 2.6 6.76 5.0 25.00 0.9 0.81 1.8 3.24 0.7 0.49 9.1 82.81 2.6 6.76 1.1 1.21 1.3 1.69 1.4 1.96 24.5 117.22 24.0 72.46 18.8 48.84 27.6 122.68 22.3 58.05 With the deviations from the mean transformed into distances, the total sum of squares will be the sum of the squared distances = 1538.47, and the corresponding number of degrees of freedom is then199, one less than the number of entries in all the samples. The between samaples sum of squares is calculated as the sum of squared distances between each sample average and grand average multiplied by ten from each sample summary. In this way I replaced each entry by its sample average. For the twenty samples these values were as follows: D (distances between sample averages and grand average) 4.8, 2.3, 2.3, 1.5, 1.8, 2.4, 2.1, 1.0, 1.5, 3.1, 2.5, 0.8, 3.4, 1.2, 1.4, 2.0, 1.8, 1.5, 2.6, 2.1 The corresponding squared values were the following: 23.04, 5.29, 5.29, 2.25, 3.24, 5.76, 4.41,1.0, 2.25, 9.61, 6.25, 0.64, 11.56, 1.44, 1.96, 4.00, 3.24, 2.25, 6.76, 4.41 The between samples sum of squares is the sum of the squared values (118.66) multiplied by ten, the number of items in each sample, and that is 1186.6. The corresponding number of degrees of freedom is one less than there are samples, i.e. 19. Now I could construct the table of analysis of variance. TABLE OF ANALYSIS OF VARIATION. _________________________________________________ Sources of Sum of Degrees of Variance variation squares freedom estimate _________________________________________________ Total 1538.47 199 - _________________________________________________ Between 1186.60 19 62.45 samples _________________________________________________ Within 351.87 180 1.96 samples _________________________________________________ The corresponding calculated F number is 62.45/1.96 = 31.86, which is much greater than either 1.84 at 0.05 level; of probability, or 2.37 at 0.01 level of probability. Conclusion: The between samples variation is highly significant when compared with the within samples variation in the points of origin of the circles. It is this kind of individual differences which form the raw materials for natural selection to work on. It should be noted that this exercise provided practice in measuring selectively meaningful variation. The results do not imply, however, that variations in the points of origins of drawn circles have any evolutionary meaning. It is always a good idea to check up on the meaning of the data from point of view of accuracy, or range of inaccuracy that might be present. The weights in grams are established by making a Xeroxed copy of the original data sheets, and then by cutting out the circles as accurately as possible with a pair of scissors and weighing the cut out circles on an reasonable sensitive analytical balance. The balance I have been using had a readout to three decimal places after the decimal point, that is in thousands of grams (0.1 milligrams). To check the accuracy of the cutting process, I Xeroxed one of the circles in 25 copies and after having cut them out carefully I weighed them each on the balance. The following weights were obtained: 0.642, 0.653, 0.628, 0.649, 0.657, 0.561, 0.660, 0.640, 0.644, 0.655, 0.632, 0.655, 0.665, 0.624, 0.647, 0.640, 0.662, 0.638, 0.648, 0.644, 0.647, 0.632, 0.654, 0.639, 0.642 It can be easily seen that the first number after the decimal point, 0.6, is constant all through the measurements except in one occation with the value of 0.5. (underlined in the above set.) As to the number in the second place, the most numerous is 0.64 (10 out of 25.) The number in the third decimal place is most variable with a complete range from 0 through 9. It is, therefore, a reasonable procedure to omit the third position figures, as it has been done in the collecting of data of weights in Part I. In addition, on a previous occasion, it has already been calculated that the balance drifts in the third decimal numbers without effecting the second. (See Sub Menu/ Variation in Beans, toward the end of section.) One final question should yet be answered. The original idea was to study the size of the circles in terms of square centimeters. To do this we were to divide the weights in grams by 0.00765 (the weight of 100 cm^2 piece of paper.) This division would make vey large numbers, difficult to work with. So I decided to omit this division and simply use the weights as the "coded data". Does this omission effect the comparison of between samples and within sample variations? When we code data by subtracting from each data the same amount, or by adding the same amount to each entry in all the samples we do not change variance because variance is independent of origin. But when we multiply or divide each entry by the same number we change the size of variance estimates. Do we also change the ratio of the larger and lesser variance estimates, that is, do we also change the value of the calculated F number? What is the answer?. Is it legitimate not to change the weights into areas by omitting the division by 0.00765 and call the weights as code for areas? Find a way to resolve this problem. End of section.*CARDU($n ? Sub Menuon mouseUp set scroll of card field 1 to 0 go to Card 43 end mouseUpn p? Main Menuon mouseUp set scroll of card field 1 to 0 go to Card 2 end mouseUp6 ??Analysis of Variance"L v L p? Figureon mouseUp go to Card 69 end mouseUp(fS0`)r_n`fO##' ANALYSIS OF VARIANCE. General Theory. Variance is measured as the sum of the squared deviations of entries from their mean, devided by the number of degrees of freedom, which is one less than the number of entries. In a formula: Variance = Sum of squares / degrees of Freedom or S^2 = ((x - x bar)^2) / (N - 1) where S^2 is variance, N is the number of entries, x bar is the average of all entries, i.e. x/N, and (N -1) is the number of degrees of freedom. For larger number of entries the number of degrees of freedom may be taken as N instead of N-1. The square root of variance is the Standard Deviation or S. To set up an Analysis of Variance or ANOVA table, we need to calculate the total sum of squares and the corresponding number of degrees of freedom, the between samples sum of squares and the corresponding number of degrees of freedom, and the within samples sum of squares and the corresponding number of degrees of freedom. From these we can obtain the variance estimates for within and between samples variations and compare them by taking their ratio as the ratio of the larger and lesser variance estimates. This gives us a value called the calculated F number, which can then be compared with theoretical values in the F table. (See Sub Menu and F Tables) By the way, once we know the total sum of squares and the between samples sum of suares, the within samples sum of squares is given by the difference between the total and the between values. The same applies to the corressponding numbers of degrees of freedom. This approach is somewhat simplistic because we omit to consider other sources of variation and covariation, but it is adequate to reach general conclusions. If we deal with single number entries, a simplified method is recommended for the ANOVA table by making use of a correction factor. (Part I) In more complex situations, as in case of (x,y) pair entries, a somewhat longer method is used. (Part II) Part I. Variation study, single value entries. The following is a step by step presentation of the procedures leading to analysis of variance in which the between samples and the within samples variations are compared. First, collect your data by sampling a set of different populations. Arrange the data in columns within each sample. Then proceed as follows: 1. Calculate the column totals. (x) 2. Square each item in the samples and calculate the column totals of the squared items. (x^2) 3. Calculate the grand total (T) as the sum of column totals. 4. Calculate the Correction Factor (CF) as T^2/N where N is the total number of entries in all the samples. 5. Next calculate the total sum of squares by taking the sum of column totals of squared items (obtained in 2 above), and subtract the Correction Factor (obtained in 4 above). 6. Determine the total number of degrees of freedom as N-1. 7. Calculate the between samples sum of squares. First square each column total (obtained in 1 above) to get (x)^2 for each sample. Then add all the squared column totals and divide this sum by n, the number of items in each sample. Finally, sub- tract the Correction Factor. 8. Determine the between samples number of degrees of freedom as one less than there are samples. 9. Calculate the within samples sum of squares as the difference between the total sum of squares and the between samples sum of squares. 10. Determine the within samples number of degrees of freedom as the difference bet- ween total number of degrees of freedom and between samples number of degrees of freedom. 11. Draw up a table of analysis of variance including the sources of variation (Total variation, Between samples variation and Within samples variation), the sum of squares (again as the Total sum of squares, and the Within and Between samples sums of squares), the corresponding degrees of freedom, and the variance esti- mates for between and within samples. The variance estimates are the ratios of a given sum of squares and the corresponding number of degrees of freedom. Cal- culate the variance estimates only for the within and the between samples vari- ances. 12. At this point, you have two variance estimates, one for between samples and one for within samples. One of these will be probably larger than the other. This is called the larger variance estimate, and the other is the lesser variance estimate. Calculate Snedecors F number as the ratio of the larger and the lesser variance estimates 13. Compare this calculated value with the one found in the F table, which you find se- lecting Sub Menu / F Tables. Take first the F distribution for 0.05 probability. The F value in the table is found at the intersection of the number of degrees of free- dom for the larger (columns) and for the lesser (rows) variance estimates. If the calculated F number is less than the one found in the table, then the difference between the two types of variance estimates is not significant. Otherwise, the difference is significant. Significance here means that the probability of coming across such difference by chance alone is five out of a hundred, that is one out of twenty. 14. In case the difference between the within and the between samples variations is significant, repeat the above procedure but use the F distribution for 0.01 proba- bility. If the calculated F number is larger than the one found in the table, then the difference between the two types of variance estimates is highly signifi- cant. Part II. Variation study, (x, y) entries. There are times when a correction factor cannot be used because the measurements are somewhat complex. For instance, if we are to study the variation of the positions of points in a two dimensional space, the values are expressed as (x,y) pairs of numbers and not as single values. Then the totals are given as (x,y), and the averages as (x/N,y/N) where N is the number of (x,y) pairs. Arrange the data, that is the sets of (x,y) pairs, in columns within each sample. Then proceed as follows: 1. First prepare a sample summary for each sample. Suppose that the points have been collected on individual sheets of 81/2" x 11" white paper presented in the "portrait" position, with the longer sides on the left and right, and the shorter ones on top and bottom. Transfer all the points in the sample onto a single sheet. List the (x,y) value of each point. Calculate the totals as (x,y). Calculate and mark the position of the sample average. From all samples, calculate the grand average and mark its position on each sample summary. Ckick on the Figure button below to see an example of such sample summary. 2. In order to calculate the total sum of squares and the between samples sum of squares, it is necessary to transform the deviations of the individual (x,y) pairs from the corresponding averages into single values. This can be done by changing the deviations into distances. To calculate the total sum of squares, measure the distance between each point of origin and the grand average point in each sample summary. Use a ruler with centimeter and millimeter divisions to determine these distances. Square each distance and tabulate the squared values on each sample summary. Sum all the squared distances to obtain the total sum of squares. The corresponding number of degrees of freedom is one less than the total number of entries in all the samples. 3. Next, calculate the between samples sum of squares and the corresponding number of degrees of freedom. In each sample summary replace the actual entries by their own average. This will eliminate the within sample variation. In other words, measure the distance between the sample average and the grand average, square this value, and multiply the squared value by n, the number of items in the sample. Do this for each sample summary. Finally, add up the values obtained in each sample summary to dertermine the between samples sum of squares. The corresponding number of degrees of freedom is one less than the number of samples, that is n-1. 4. Calculate the within samples sum of squares and the corresponding number of deg- rees of freedom as the difference between the total sum of squares and the between samples sum of squares, and the total number of degrees of freedom and the between samples number of degrees of freedom. 5. Finally, determine the significance of the difference between the within and between samples variations by comparing the magnitude of the calculated F number with that given in the F distribution table for 0.05 and 0.01 probabilities. The procedure is the same as given in the previous analysis above in entries 11-14. End of section.CARDV(~n ? Sub Menuon mouseUp set scroll of card field 1 to 0 go to Card 43 end mouseUpn p? Main Menuon mouseUp set scroll of card field 1 to 0 go to Card 2 end mouseUp* ??F Tables"Jl y*&GJ,@ F DISTRIBUTION 0.05 PROBABILITY Degrees of Freedom of Greater Variance Estimate * 2 3 4 5 6 7 8 9 10 20 30 40 2 19.00 19.16 19.25 19.30 19.33 19.35 19.37 19.38 19.40 19.45 19.46 19.47 3 9.55 9.28 9.12 9.01 8.94 8.89 8.85 8.81 8.79 8.66 8.62 8.59 4 6.94 6.59 6.39 6.26 6.16 6.09 6.04 6.00 5.96 5.80 5.75 5.72 5 5.79 5.41 5.19 5.05 4.95 4.88 4.82 4.77 4.74 4.56 4.50 4.46 6 5.14 4.76 4.53 4.39 4.28 4.21 4.15 4.10 4.06 3.87 3.81 3.77 7 4.74 4.35 4.12 3.97 3.87 3.79 3.73 3.68 3.64 3.44 3.38 3.34 8 4.46 4.07 3.84 3.69 3.58 3.50 3.44 3.39 3.35 3.15 3.08 3.04 9 4.26 3.86 3.63 3.48 3.37 3.29 3.23 3.18 3.14 2.94 2.86 2.83 10 4.10 3.71 3.48 3.33 3.22 3.14 3.07 3.02 2.98 2.77 2.70 2.66 20 3.49 3.10 2.87 2.71 2.60 2.51 2.45 2.39 2.35 2.12 2.04 1.99 30 3.32 2.92 2.69 2.53 2.42 2.33 2.27 2.21 2.16 1.93 1.84 1.79 40 3.23 2.84 2.61 2.45 2.34 2.25 2.18 2.12 2.08 1.84 1.74 1.69 * Lesser Variance Esdtimate. F DISTRIBUTION 0.01 PROBABILITY Degrees of Freedom of Greater Variance Estimate 2 3 4 5 6 7 8 9 10 20 30 40 2 99.00 99.17 99.25 99.30 99.33 99.36 99.37 99.39 99.40 99.45 99.47 99.48 3 30.82 29.46 28.71 28.24 27.91 27.67 27.49 27.35 27.23 26.69 26.50 26.41 4 18.00 16.69 15.98 15.52 15.21 14.98 14.80 14.66 14.55 14.02 13.84 13.75 5 13.27 12.06 11.39 10.97 10.67 10.46 10.29 10.16 10.05 9.55 9.38 9.29 6 10.92 9.78 9.15 8.75 8.47 8.26 8.10 7.98 7.87 7.40 7.23 7.14 7 9.55 8.45 7.85 7.46 7.19 6.99 6.84 6.72 6.62 6.16 5.99 5.91 8 8.65 7.59 7.01 6.63 6.37 6.18 6.03 5.91 5.81 5.36 5.20 5.13 9 8.02 6.99 6.42 6.06 5.80 5.61 5.47 5.35 5.26 4.48 4.65 4.57 10 7.56 6.55 5.99 5.64 5.39 5.20 5.06 4.94 4.85 4.41 4.25 4.17 20 5.85 4.94 4.43 4.10 3.87 3.70 3.56 3.46 3.37 2.94 2.78 2.69 30 5.39 4.51 4.02 3.70 3.47 3.30 3.17 3.07 2.98 2.55 2.39 2.30 40 5.18 4.31 3.84 3.51 3.29 3.12 2.99 2.89 2.80 2.37 2.20 2.11 * Lesser Variance Esdtimate Note: If the number of degrees of freedom of either the greater or the lesser variance esti- mates is greater than 40, then use the entries at 40. End of section.CARDWXGpx p? Main Menuon mouseUp set scroll of card field 1 of card 65 to 0 go to Card 2 end mouseUp. ??Draw a Circlex ? Sub Menuon mouseUp set scroll of card field 1 of card 65 to 0 go to Card 43 end mouseUpR o? Back to Texton mouseUp go to Card 65 end mouseUpBMAPXGLVL" ^Vg n9T /^80 !  >" M " @  ] P l<( l< ;R `Cp`( ;C 6`& (&*60 (xa6 @ )& Ugn8 )0dNG@ )@ )0( C5 6&) @ &*&*&*<xxx8<    @ <x,,,,  @    D * * D*@ |&&(&((|>?)0 ) & )&  &@ ?(($($:#p+8#`kk?+8;, A  8 (x" 9c& 9 $0 " D $I$I$I"  ` A "b  & Sps00p0c0x`:`:`"8&|"R!""YC>|@|  ->"| '!@@$4  q dΦU%)"*h*I N$&U%)  QA)JHJH RHIA)Jep30Rp3dH @c@ RH @ThAJp2 ppAJFB [1¬3 c %u:{9w< g 30 ` "9tpq %sp8  BB@BB?B:4 "648>x "@64` p +a48 "`%< "&& :4| #5C8 5C|>x +C@ p #`5A4  #0%% %50 #54\ B B B$<%4`C80 "%d3C|>p =g4a`4<> /04@4

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The part of the geological history of the earth most connected with the fossil record goes back approximately 570 million years to the beginning of the Paleozoic Era. This period of time is divided into three major Eras, each separated by a major geological event. The three Eras are the Paleozoic. Mesozoic, and the Cenozoic Eras. The Paleozoic is separated from the previous, Precambrian times by the Great Revolution. Here in the United States, the Paleozoic is separated from the Mesozoic by the Appalachian Mountain Revolution, and the Mesozoic from the Cenozoic by the Rocky Mountain Revolution. The beginning of the Paleozoic Era was 570 million years ago and its duration was 345 million years. The beginning of the Mesozoic was 225 million years ago, and its duration was 160 million years. Finally, the Cenozoic began 65 million years ago and ends at the present time. Each of the three Eras are divided into Periods. The Periods of the Cenozoic are also divided into Epochs. The names of these Periods are listed below with their durations in millions of years following each name. Thus we have: Era Beginning Periods: Epochs Duration Great Revolution Paleozoic 570 345 Cambrian 70 Ordovician 70 Silurian 35 Devonian 50 Mississippian 20 Pennsylvanian 45 Permian 55 Appalachian Mountain revolution Mesozoic 225 160 Triassic 35 Jurassic 55 Cretaceous 70 Rocky Mountain Revolution Cenozoic 65 65 Tertiary 62.5 Paleozene 11 Eocene 16 Oligocene 12 Miocene 19 Pliocene 4.5 Quaternary 2.5 Pleistocene 2.5 Recent 0 The following table shows the appearance of animal and plant life in the various periods together with the climatic and the geological conditions of the given times. PERIOD ANIMALS PLANTS CLIMATE, (GEO.) ERA _________________________________________________________________________ CAMBRIAN Most phyla Blue-green algae As today PALEOZOIC Trilobites (Low land) Brachiopods (Geosynclines) ORDOVICIAN Ostracoderms E Green algae Warming Plants I land (Inundation) SILURIAN Placoderms E Land plants R Peak warming Eurypterids Psilophytes (Slow uplift) Arthropods I land Club mosses Horsetails Sphenopsids Ferns DEVONIAN Amphibians E Forests E Cooling Lungfish, Shark Gymnosperms E (Glacial mount) Bony fish R (Inland seas) Winged insects MISSISSIPPIAN Sharks R Forests S Warming Amphibians Humidity rises Winged insects (Mountain build) PENNSYLVANIAN Amphibians R Coal swamp forest Peak warming Reptiles E Seed ferns Peak humidity Giant insects True mosses (Coal measures) PERMIAN Reptiles R Glossopteris Intense cold (Ice Modern insect OR Plants D age) then warm _________________________________________________________________________ TRIASSIC Dinosaurs R Gymnosperms Warming, dry MESOZOIC Primitive amph. D Cycads, Ginkgos (Exposed conti- Conifers nents, deserts) Angiosperms E Seed ferns D JURASSIC All reptiles Same as before Warming Birds E Dicotyledons E Very dry CRETACEOUS Dinosaurs D Monocotyledons Cooling Primitive birds D Angiosperms (Inundation then Archaic mammals Flowers mountain build.) Maple, oak forests _________________________________________________________________________ PALEOCENE Prim. mammals Subtropical Warming CENOZOIC (Tertiary) Modern birds EOCENE OR SOR of Mamm. Subtropical Warming OLIGOCENE FA of Mamm. Temperate Seasonal Prim. mammals D MIOCENE Anthropoids R Grasslands E Seasonal Grazing mamm.E,R SFA of Mamm. PLIOCENE Humans Grasslands S Seasonal GE of Mamm. _________________________________________________________________________ PLEISTOCENE Stages of Human E Grasslands Seasonal CENOZOIC (Quaternary) Cultural E Overkill SP of Mamm. RECENT Human history Herbaceous plants Seasonal _________________________________________________________________________ Legend: E evolve(s) R radiate(s) I invade(s) D decline(s) S spread(s) (GEO,) geological events OR mod. orders SOR suborders FA families SFA subfamilies GE genera SP species Note: Fossils from the Precambrian Era are few and rather strange, and they do not seem to fit well into the later systems. Fossils do not last forever. Erosion, crystallization and meltdown are the chief causes of destruction of fossils. End of section.5 CARDS`23n ? Sub Menuon mouseUp set scroll of card field 1 to 0 go to Card 43 end mouseUpn p? Main Menuon mouseUp set scroll of card field 1 to 0 go to Card 2 end mouseUp4 ??Variation in Beans"Jl 3=HO:@J~    Mg^|    !x!!"$$)^)m++6..2 VARIATION IN BEANS. The purpose of the experiment is to become familiar with handling the mathematics of variation. This is achieved by measuring the amount of phenotypic variation in three samples of beans. If it can be shown that the variation between samples (or between individuals) is greater than the within sample variation, we have established the presence of a situation in which natural selection can be effective, provided some of the phenotypic variation is due to genetic causes. This is a simple exercise in the study of phenotypic variation. The amount of genetic effect which contributes to this variation is not investigated here. Materials and methods. In this experiment we measure the weights of three types of beans, 100 in each. The beans were Lima beans, Kidney beans, and Black-eyed peas. It is convenient to use an electronic balance with digital read-out in grams to three decimal places. First, the balance should be zeroed out. Then each bean is weighed and the weight is recorded rounding off the third digit to two figures after the decimal point. Before you begin measuring the beans, select one hundred at random from a given type. Put the beans on the table and do not hold them in your hand. It is a good idea to remove the beans from the balance by the use of a brush or a strip of paper. Instead of picking them up by hand, simply push the beans off the pan of the balance. It takes about 20 minutes to measure 100 beans. The raw data from an actual experiment are tabulated below. Data: 100 KIDNEY BEANS (Weights in grams.) x = 54.90 g 0.63 0.82 0.59 0.72 0.60 0.54 0.60 0.62 0.41 0.59 0.58 0.63 0.62 0.53 0.46 0.66 0.39 0.57 0.54 0.44 0.40 0.43 0.67 0.46 0.48 0.63 0.63 0.50 0.57 0.51 0.47 0.60 0.57 0.55 0.56 0.47 0.62 0.50 0.50 0.59 0.55 0.58 0.68 0.43 0.61 0.49 0.60 0.55 0.69 0.69 0.53 0.51 0.42 0.72 0.48 0.37 0.57 0.58 0.52 0.38 0.49 0.64 0.49 0.55 0.67 0.49 0.66 0.38 0.51 0.43 0.47 0.42 0.42 0.53 0.59 0.47 0.52 0.65 0.42 0.58 0.71 0.50 0.59 0.64 0.53 0.35 0.51 0.50 0.52 0.54 0.75 0.63 0.57 0.63 0.59 0.53 0.45 0.61 0.54 0.70 100 LIMA BEANS (Weights in gram) y = 92.82 g 1.39 1.17 0.75 0.86 1.25 1.24 1.07 0.61 1.22 0.94 0.90 0.81 1.08 0.78 0.87 1.18 0.89 1.02 0.95 0.95 0.79 0.71 0.83 0.72 0.81 1.07 1.06 0.80 1.07 0.74 1.12 0.66 0.70 1.02 1.13 0.76 0.98 1.14 0.68 0.92 0.93 0.90 0.80 0.52 1.00 1.08 1.16 0.82 1.07 1.03 1.09 1.00 1.24 0.90 0.81 0.92 0.96 0.73 1.08 1.00 0.70 0.85 0.93 0.81 0.58 0.92 0.71 1.01 0.93 0.77 0.78 0.89 0.78 0.97 1.04 1.20 1.02 0.89 0.59 0.91 1.18 0.84 0.95 1.10 1.09 0.65 0.96 1.18 0.73 1.04 0.79 0.62 0.49 1.09 1.28 0.89 0.94 1.00 0.97 1.04 100 BLACK-EYED PEAS (Weights in grams) z = 22.75 g 0.21 0.10 0.13 0.17 0.26 0.12 0.24 0.21 0.17 0.30 0.17 0.24 0.29 0.20 0.25 0.21 0.23 0.27 0.22 0.25 0.21 0.33 0.27 0.13 0.29 0.13 0.25 0.24 0.20 0.28 0.20 0.16 0.26 0.33 0.27 0.25 0.30 0.23 0.20 0.29 0.20 0.26 0.21 0.22 0.23 0.29 0.20 0.19 0.22 0.23 0.27 0.26 0.30 0.18 0.24 0.24 0.27 0.25 0.18 0.25 0.26 0.14 0.25 0.20 0.17 0.12 0.24 0.17 0.25 0.18 0.26 0.19 0.31 0.16 0.18 0.17 0.35 0.31 0.34 0.28 0.18 0.21 0.26 0.24 0.26 0.26 0.23 0.19 0.12 0.22 0.16 0.24 0.22 0.23 0.23 0.21 0.22 0.19 0.24 0.27 Next, I squared each entry and calculated the sum of the squared items in each sample. I arranged the individual entries according to magnitude and frequency to avoid the repeated squaring of the same numbers. KIDNEY BEANS: x2 = 30.712 0.123 0.137 0.289 (0.144 x 2) 0.152 0.168 0.353 (0.176 x 4) 0.555 (0.185 x 3) 0.194 0.203 0.423 (0.212 x 2) 0.884 (0.221 x 4) 0.461 (0.230 x 2) 0.960 (0.240 x 4) 0.160 1.040 (0.260 x 4) 0.811 (0.270 x 3) 1.405 (0.281 x 5) 1.166 (0.292 x 4) 1.210 (0.302 x 4) 0.314 1.625 (0.325 x 5) 1.346 (0.336 x 4) 2.089 (0.348 x 6) 1.250 (0.250 x 5) 0.744 (0.372 x 2) 1.922 (0.384 x 5) 1.588 (0.397 x 4) 0.819 (0.410 x 2) 0.423 0.872 (0.436 x 2) 0.898 (0.449 x 2) 0.462 0.952 (0.476 x 2) 1.440 (0.360 x 4) 0.504 1.037 (0.518 x 2) 0.563 0.490 0.672 LIMA BEANS. y2 = 89.413 0.240 0.270 0.336 0.348 0.372 0.384 0.423 0.436 0.462 0.980 (0.490 x 2) 1.008 (0.504 x 2) 1.066 (0.533 x 2) 0.598 0.563 0.578 0.593 1.217 (0.608 x 2) 1.872 (0.624 x 2) 1.280 (0.640 x 2) 2.624 (0.656 x 4) 0.672 0.689 0.706 0.723 0.749 3.961 (0.792 x 5) 2.430 (0.810 x 3) 0.828 2.539 (0.846 x 3) 2.595 (0.865 x 3) 1.767 (0.884 x 2) 2.708 (0.903 x 3) 1.843 (0.922 x 2) 1.882 (0.941 x 2) 0.960 4.000 (1.000 x 4) 1.020 3.121 (0.040 x 3) 1.061 3.245 (1.082 x 3) 1.124 4.580 (1.145 x 4) 3.499 (1.166 x 3) 3.564 (1.188 x 3) 1.210 1.254 1.277 1.300 1.346 1.369 4.177 (1.392 x 3) 1.440 1.488 3.075 (1.538 x 2) 1.563 1.638 1.932 BLACK-EYED PEAS. z2 = 5.476 0.010 0.043 (0.014 x 3) 0.051 (0.017 x 3) 0.020 0.077 (0.026 x 3) 0.073 (0.029 x 6) 0.162 (0.032 x 5) 0.144 (0.036 x 4) 0.240 (0.040 x 6) 0.309 (0.044 x 7) 0.288 (0.048 x 6) 0.370 (0.053 x 7) 0.518 (0.058 x 9) 0.504 (0.063 x 8) 0.608 (0.068 x 9) 0.437 (0.073 x 6) 0.157 (0.078 x 2) 0.421 (0.084 x 5) 0.270 (0.090 x 3) 0.192 (0.096 x 2) 0.218 (0.109 x 2) 0.116 0.123 Finally, I obtained the between and the within sample variance estimates as the ratios of the corresponding sum of squares and degrees of freedom. I obtained a calculated F number as the ratio of the greater and the lesser variance estimates. Then I compared this F number with the corresponding value in the F table. As a rule, If the calculated value is less than the one in the table at 0.05 probability than the difference between the between and within samples variations is not significant. Otherwise, it may be significant or highly significant. (To check up on statistical concepts and procedures select Sub Menu / Analysis of Variance. To see the F Tables, select Sub Menu / F Tables.) I also performed the following calculations: Correction Factor (CF) = Grand total squared (T2)/N where N is the total number of items in all samples, i.e. 300. T = 170.47 g, and T2 = 29060.02.. CF = 86.867 Total sum of squares = total of squared items - CF = 125.601 - 86.867 = 28.73. Total degrees of freedom = 299. Between samples sum of squares = sum of the squared sample totals divided by 100 (the number of items in each sample) - CF = 517.563 + 8615.552 + 3014.010 = 12147.125 12147.125/100 = 121.471 and 121.471 - CF = 24.604. The between samples degrees of freedom is one less than the number of samples = 2. The within samples sum of squares and the within samples degrees of freedom is the difference between the total and the between samples sum of squares and degrees of freedom. Thus: 4.126 and 297 respectively. Putting all these calculations together, I obtained the following table of analysis of variance: TABLE OF ANALYSIS OF VARIATION. _________________________________________________ Sources of Sum of Degrees of Variance variation squares freedom estimate _________________________________________________ Total 28.730 299 - _________________________________________________ Between 24.604 2 12.302 samples _________________________________________________ Within 4.126 297 0.014 samples _________________________________________________ The calculated F number is the ratio of the greater and lesser variance estimates = 12.302/0.014 = 878.714. The corresponding numbers in the F table are 3.23 and 5.18 at 0.05 and 0.01 probabilities respectively. It follows that the difference between the two variations is highly significant in favor of between samples. (To see the F table, select Sub Menu / F Table.) Conclusion. Beans are agricultural products and as such they must be maintained at an expected quality for marketing. As a result, the within samples variation is kept at minimum while the between samples variation is large. This large variation is an expression of the natural genetic richness of the genus and has its source in the evolution process. Human intervention enhances and maintains the already given natural diversity. Further considerations.. I was wandering, how accurate are the measurements using the electronic balance. To test accuracy, I first measured the same bean ten times in the same way as I did in the experiment by rounding off the digit at the third decimal place. The selected bean was a medium sized Lima bean. All ten measurements were the same at 0.96 g. Next I measured the same bean, again ten times, without rounding off the third digit. The following set of measurements were obtained: 0.963 0.957 0.959 0.957 0.959 0.963 0.960 0.960 0.964 0.965 In this last set of repeated measurements the third digit seems to float freely. Nonetheless, it became clear that by using the rounding off process these seemingly random fluctuations of the third digit are most effectively eliminated resulting in a set of well repeatable and accurate measurements. Finally, I investigated the nature of the random fluctuations of the third digit by first closing the lid of the balance to eliminate all movements of the air, and then zeroing out the balance. For the balance I was using, a star on the digital readout panel showed that the balance was zeroed out. When this star appeared the readout was 0.000 and it did not disappear all through the observation, which lasted 2 minutes. The third zero after the decimal point, however, changed approximately eight times per minute giving the following sequence of values: 0, -1, 0, +1, 2, 3, 4, 5, 6, 7, 6, 5, 4, 3, 4, 5, 6, 7, 6, 5, 4, 3, 2, 1, 0, -1, -3, -4, -3, -2, -3, -4. The nature of the drifting seemed to be random and the range remained within one hundredth of a gram. Consequently, the .rounding off method used in the experiment effectively neutralizes this random effect. In conclusion, the data in the experiment may be considered as satisfactorily accurate. End of section.7`7 FREEFree Object on (fusion) and modification of the anterior segments of the skeletal and the nervous systems resulting in the formation of a cranium and a brain, and in the concentration of sense organs in that region. (Note: Although the word, cephalization, implies the modification of the anterior region of animals, a similar process has occurred in a number of other body regions (the aortic arches of the heart, the fusion of vertebrae in the pelvic region and so on.) End of definitions.@CARD^TzA? Jaw Suspensionson mouseUp go to card 74 end mouseUpXA? Temporal Vacuitieson mouseUp go to card 75 end mouseUpL*@W? Kidneyson mouseUp go to card 83 end mouseUpVV@? From Fin to Limbon mouseUp go to card 77 end mouseUpX*WA? Cusps and Mandibleson mouseUp go to card 78 end mouseUpPz@? Molar teethon mouseUp go to card 79 end mouseUpZ@? Air Bladder and Lungon mouseUp go to card 80 end mouseUpP @? Dentitionson mouseUp go to card 81 end mouseUpN @+? Pelviseson mouseUp go to card 82 end mouseUpX A? Vertebrate Hearts on mouseUp go to card 76 end mouseUpN  p? Main Menuon mouseUp go to Card 2 end mouseUpN ? Sub Menuon mouseUp go to Card 70 end mouseUp09r? Special Studies4 8? Comparative AnatomyPVA? Placentaeon mouseUp go to card 101 end mouseUpT+A? Aortic Archeson mouseUp go to card 108 end mouseUp@CARD_\n p? Main Menuon mouseUp set scroll of card field 1 to 0 go to Card 2 end mouseUp0 8? Special Studiesn ? Sub Menuon mouseUp set scroll of card field 1 to 0 go to Card 73 end mouseUp09v? Jaw Suspensions"E w L m? Diagramon mouseUp go to Card 93 end mouseUpW"C6 SPECIAL STUDIES: JAW SUSPENSIONS. The arrangements of jaw suspension is a good example to show the process of cephalization and they also present a rich source to illustrate the meaning of homology. The sequence of the representatives of the process are the Ostracoderms, primitive, extinct, agnathous fish, show- ing the old paleostylic arrangement; the Placoderms, primitive, extinct gnathostomatous fish showing the euautostyc jaw suspension; some primitive, extinct sharks with euamphistylic arrangement; advanced sharks and other advanced fishes with hyostyly; primitive, non-mam- malian tetrapods such as amphibians and lungfishes with metautostyly; advanced, non-mam- malian tetrapods such as reptiles and birds showing cranioautostyly; and mammals with the most recent craniostyly. The various names of jaw suspensions are descriptive. They express the relationship bet- ween the primitive visceral arches to one another and to the cranium. Paleostyly is the most primitive form of all the arrangements. In paleostyly, posterior to the cranium, there were a series of at least ten metameric units of gills and their supportive skeletal structures the visceral arches. As cephalization progressed to euautostyly, the visceral arches moved for- ward to the cranium and became reduced in number. The remaining first arch, also known as the mandibular arch, formed the upper and lower jaws in gnathostomatous Placoderms. The upper part of the arch became the upper jaw or palatoquadrate bar, and the lower part became the lower jaw or Meckel's cartilage. The second visceral arch was not yet supportive to the mandibular arch, hence the name euautostyly. In more advanced fishes the second visceral arch or hyomandibular arch moved forward enough to support the jaws. The gill slit between the mandibular and hyomandibular arches became the spiracle, as in modern sharks. This is the hyostylic arrangement. Very similar to hyostyly is the arrangement of amphystyly in some primitive fishes characterized by the fusion of the palatoquadrate bar with the cranium at two points. From this line we can derive much of the jaw suspension arangements of the tetrapods. In the tetrapod line the gills became much reduced in number or disappeared altogether, and the hyomandibular became free from supporting the jaws. The upper portion of the hyomandibular arch became the columella auris or the ear ossicle in both primitive (metautostylyic) and more advanced (cranioautostylic) non-mammalian tetrapods. The lower portion became incorporated into the skeletal support of the larynx. In reptiles and birds the palatoquadrate bar fused completely with the cranium and became represented by the quadrate and the palatine bones. In the craniosylic mammals the proximal segment of the lower jaw, the quadrate bone, and the upper part of the original hyomandibular arch formed the three ear ossicles, the malleus, in- chus, and stapes respectively. In the absence of the quadrate, the lower jaw now articulates with the squamosal bone. Associated with the palatine bone there is a new structure known as the alisphenoid with a canal passing through it. This bone is part of the ventral floor of the cranium and is a new development of unknown origins. Since the vertebrates, speaking in terms of the evolution process, form a related, natural group, it is correct to say that some of the bones of the palate, and the dentary of the lower jaw are homologous with the mandibular arch of the Ostracoderms. Similarly, there is homo- logy between the upper portion of the huomandibular arch of paleostyly and the columella auris of amphibians as well as the mammalian stapes. And again, there is homology between the lower portion of the hyomandibular arch and the hyoid of the larynx. The forward movement of the visceral arches and the reduction of their numbers show some of the characteristics of the cephalization process. Click on the Diagram button below to find a set of diagrams showing the various arrangements of jaw suspensions from paleostyly to craniostyly. End of section. CARD`F n p? Main Menuon mouseUp set scroll of card field 1 to 0 go to Card 2 end mouseUp0 8? Special Studiesn ? Sub Menuon mouseUp set scroll of card field 1 to 0 go to Card 73 end mouseUp49v? Temporal Vacuities"J u Lt? Diagramon mouseUp go to card 95 end mouseUp ǀ2B6    SPECIAL STUDIES: TEMPORAL VACUITIES. Temporal vacuities are depressions or holes in the bones of the skull over the temporal re- gion. Whenever dipressions or crests are formed, their function is to increase the surface of bones for the attachment of muscles in that area. The temporal region accommodates the muscles of the jaws of reptiles and of birds and mammals which have been derived from the primitive reptilian stock. In primitive turtles, as in the extinct Cotylosaurs, no vacuities were formed. Such turtles represented the anapsid condition. (Note: apsis means the round opening or round roofed win- dow of a building, and anapsid refers to the absence of such opening.) The condition is similar in modern turtles (Chelonia) with an added emargination of the back of the skull for support of the neck muscles. The presence of two temporal vacuities, one upper and another lower in position characterizes the diapsid condition. This arrangement was found in extinct dinosaurs and in modern forms such as alligators and crocodiles. Archosauria, which gave rise to birds, show a modified diapsid condition in which an added vacuity appears between the nares and the orbit. All these vacuities become confluent in modern birds. In modern lizards the lower temporal vacuity of the diapsid condition became ventrally emarginated. In some ancient and now extinct reptiles only the upper vacuity was present. These were the parapsid reptiles and were represented by such forms as Plesiosaurus and Ichthyosaurys. The synapsids or mammal-like reptiles had a single lower vacuity. In modern mammals, this vacuity, in the absence of a post orbital bar, often becomes confluent with the orbit. The presence or absence and the appearance of these temporal vacuities are highly charac- teristic features in the classification of extinct reptiles and their modern, living descendants. As a rule, the bones involved in the formation of these vacuities are the following: In a diapsid condition, the upper vacuity is bordered by the parietal, postorbital and the squamosal bones, while the lower vacuity is formed by the postorbital, squamosal, jugal, and quadrate. This arrangement is maintained even in the parapsid and synapsid conditions in reference to the upper or the lower vacuities respectively. The only exception to this rule was the fish- like Ichthyosaurus where the single upper vacuity was shifted to the top of the skull and was associated with the parietal bones. Click on the Diagram button below to find the visual presentation of the various arrange- ments of temporal vacuities. End of section. CARDc& n p? Main Menuon mouseUp set scroll of card field 1 to 0 go to Card 2 end mouseUp0 8? Special Studiesn ? Sub Menuon mouseUp set scroll of card field 1 to 0 go to Card 73 end mouseUp.9v? Cusp PatternsNu? Diagramon mouseUp go to card 103 end mouseUp"F o  Ҁ!@  SPECIAL STUDIES: CUSP PATTERNS. The mammals of today can be derived from Therapsid origin as far back as the Middle Per- mian. Some of these therapsids, the Theriodonts (the name means mammalian teeth), were the most mammal-like of all reptiles. Their dention consisted of incisors, canine, and cheek teeth just as in mammals, and many other features of their skeletons were also similar to mammals. The earliest true mammals, however, did not appear until the late Triassic of Britain, south Africa, and China. All of these were rather similar to each other and all were small shrew-like animals. Their fosssil record shows cheek teeth with rows a three cusps, one in the front, another, the largest, in the center, and a third in the rear. Their mandibles hinged between the squamosal and the dentary bones, indicating the presence of three ear ossicles. From these we can trace two major, Jurassic, evolutionary lines, the triconodonds and multituberculates for one, and the symmetrodonts and panthotheres for the other. The triconodons showed the basic arrangement of the above described triple cusps, the multituberculates had double rows of three cusps, while the symmetrodons had the three cusps arranged in a triangular fashion. Their lower jaws consisted of the typical mammalian dentary, a single bone which, however, was primitive because it had only two processes, the coronoid and the articular. The angular process later mammals was absent. From the evolutionary viewpoin, the panthotheres were the most important of all Mesosoic mammals, because they are the ancestors to both, marsupials and placental mammals, that is to all living mammals except for the monotremes (the egg laying mammals). The dentary of the panthotheres included the angular process in addition to the coronoid and the articular, just as it is found today in marsupials and placental mammals. The cheek teeth of pantho- theres developed a talon or heel on which several smaller cusps appeared in more modern mammals. It should be noted that in marsupials the angular process of the dentary is turned toward the ventral midline at ninety degrees, and it is called the inflected angle. This inflected angle is a characteristic feature of all marsupials and allows the lower jaw to be opened much wider than it is possible for the placental mammals. Click on the Diagram button below to see the above described arrangements. End of section.`FREEFree Object the various arrangements. End of section. CARDb% 8n p? Main Menuon mouseUp set scroll of card field 1 to 0 go to Card 2 end mouseUp0 8? Special Studiesn ? Sub Menuon mouseUp set scroll of card field 1 to 0 go to Card 73 end mouseUp29v? From Fin to LimbPu? Diagram 1on mouseUp go to card 105 end mouseUpPtؠ? Diagram 2on mouseUp go to card 106 end mouseUpP;? Diagram 3on mouseUp go to card 107 end mouseUp"I r P :? Diagram 4on mouseUp go to card 120 end mouseUp4%G  !EFRS0>Xf x    L S e s   SPECIAL STUDIES: FROM FIN TO LIMB. In this study we compare the bone components of the forelimbs of tetrapods, and compare them with the endoskeletons of pectoral fins in various fishes. The skeleton of the tetrapod limb is composed of a single long bone, the humerus in the forelimb and the femur in the hind limb. The humerus articulates with the scapula at the shoulder, and with two long bones, the radius and the ulna at the elbow. The femur articulates with the ilium of the pelvis and with two long bones, the tibia and the fubula at the knee. The most distal bones are the carpals, metacarpals, and the phalanges or digits in the foreleg or arm. The corresponding bones of the hind leg are the tarsals, metatarsals and the phalanges or toes. Both forelegs and hindlegs are originally pentadactyl there being five digits and five toes respectively. As the primitive vertebrates invaded the land from water (sea or fresh water), the struc- ture of the fins underwent some characteristic changes leading to the pentadactyl arrange- ment. We can trace these changes in the structure of pectoral fins in the three primitive sharks, Cladoselache, and Cladodus the earliest known sharks from the upper Devonian, and Pleuracanthus, a fresh water offshoot most abundant in the Carboniferous. (Diagram 1) In this short morphocline series a trend can be seen from the rather rigid pectoral fins (Cladoselache) to a highly movable structure (Pleuracanthus). In Cladoselache there is a basal axis and a row of basal radials and both of these are firmly attached to the scapula. The fin is given rigidity by the set of distal radials. In Cladodus the area of attachement between the basal radials is reduced and a central axis has developed carrying a set of distal radials. In Pleuracanthus the central axis articulates with the scapula at one movable point and carries the preaxial (upper) and postaxial (lower) radials. Further developments of the central axis can abe seen in lungfishes. In Diagram 2, two lines of development are shown. One is represented by Neoceratodus an Australian lungfish which still shows the primitive arrangement of a movable central axis with symmetrical preaxial and postaxial radials. This arrangement is knows as the archipterygium (ancient fin). The other line shows a reduction and fusion of bone elements as in Eusthenopteron from the Upper Devonian. This latter arrangement is called the ichthyopterygium (fishlike fin). Finally, as shown by Eogyrinus, a pedominantly aquatic amphibian from the Carboniferous, and Eryops, a stout-limbed terrestrian amphibian from the early Permian in Diagram 3, the pentadactyl arrangement of limbs has been realized. In these appandages the scapula arti- culates with a single bone the humerus, which in its turn articulates with the radius and ulna. The number of carpals, and metacarpals is variable, and the digits only approximate the number five. The tetrapod lims undergo many and various modifications in the evolution of special groups. One of the best known of these is the evolution of limbs in Perissodactyls (horses) and Artiodactyls (ruminants or even hoofed mammals, such as the cow, deer, antilope). The original horses were small pentadactyl animals. They responded to the constant pressure of need to escape from predators by increasing the running speed by lengthening the gait chang- ing from a five toed, plantigrade stance where all carpals, metacarpals and phalanges were in contact with the ground to a digitigrade gait, running with elevated heels and having only the digits flat on the ground, and then to a unguligrade gait running on tiptoes with the nails of the digits on the ground. In the horses only the middle toe remains developed and the nail changes into a hoof. In the ruminants the digits three and four remain producing the split even hoofed limbs. Parallel with the trend raising the body higher off the ground to lengthen the stride ran another trend which was to increase the size of the body. Today's horses are relatively large animals. See Diagram 4 for a comparison of the limbs in odd and even hoofed mammals. End of section.!CARDzn ? Sub Menuon mouseUp set scroll of card field 1 to 0 go to Card 115 end mouseUpn p? Main Menuon mouseUp set scroll of card field 1 to 0 go to Card 2 end mouseUp. 8? Geochronology"H p Nt? Pictureson mouseUp go to card 26 end mouseUp&NQ^  | GEOCHRONOLOGY. Geochronology is about measuring time on a geological time scale in millions of years. There are two scales we may use, one is in relative time, the other in absolute time. Relative time reveals temporal sequences better than temporal duration of events. The reason for this is simple. Take for instance the thickness of deposits. The thicker the depo- sit the longer it took to make it. But we do not actually know the rate of deposition, conse- quently, it is not possible to estimate the duration of events or to compare the duration of two events based on thickness of strata. The same can be said about the salinity of the ocean which would relate to the original salinity of the ocean, the rate of evaporation, and the rate of uptake of minerals by the rivers from the continental soil. None of these factors are known for sure. On the other hand, temporal sequences of events are well provided for in relative dating. Based upon the principle of superposition, it can be said that whatever is deeper is older. Of course, temporal sequences can be disrupted by erosion, and by the fold- ings of strata. It is, therefore, a good practice to study first the geological history of a given locality before the principle of superposition is applied for relative dating. Absolute time is measured by making use of the precise decaying time of radioactive isotopes expressed as half life in years. Half life means the time required for half of the original amount of redioactive material to decompose to a stable form. This half life is independent of the amount of the original material in the sense that x gram of material takes as long to decompose to x/2 gram, as x/2 gram takes to decompose to x/4 gram. Knowing the half life of a given radioactive isotope it is possible to measure time in years from the amount of stable end products and remaining original materials present. This is particularly useful to date fossil materials, including imprints, which are associated with radioactive isotopes in the sediment surrounding them. The usual isotopes used for dating in paleontological work are uranium-238/lead-206 with half life 4.5 x 10^9 years, uranium-235/lead-207 with half life 0.7 x 10^9 years, thorium-232/lead-208 with half life 14 x 10^9 years, potassium-40/argon-40 with half life 1.3 x 10^9 years, and rubidium-87/strontium-87 with half life 5 x 10^10 years. The uranium and thorium series include radon in their transitional isotopes. Radon being a gas can easily escape and lead to low estimates. The same is the problem with argon which is again a gas. For potassium/argon and rubidium/strontium dating one of the most useful minerals is glauconite brecause it preserves most of the decomposition products. It should be noted that in the potassium/argon method only 11% of potassium-40 decomposes to argon-40. The other 89% forms calcium-40, a fairly common mineral in deposits from divers sources. Another isotope. carbon-14/carbon-12 is often used in dating. The half life of the transition is 5730 years with a limit of dating around 70,000 years. The method is useful for archeological work, but because of the short half life it cannot be used in paleontology. Correlation of deposits is a method that combines relative and absolute dating by making use of index fossils. Suppose that a chronological sequence of deposits has been dated in years at a given place. If one or more of the layered deposits carry index fossils and these index fossils are found at a number of other places, then the age of the deposits at the other places is the same as that of the corresponding layer at the original site. Radioactive dating is laborious and expensive. By using the correlation of deposits method much of the labor and expense can be reduced. What are index fossils? Any fossil can be used as index for dating provided 1. It is clearly identifiable. 2. It has been fairly common and has been distributed world-wide. 4. It existed for a short period of time. (Otherwise it could not be used for precise dating.) Some mollusks, foraminifers, pollen grains, and spores are good candidates to be index fossils. See Pictures for some index fossils and the way they are used. End of section.!n.!FREEFree Object The outer layer of the tooth is not enamel but cement, a semi hard bone-like material. Underneath this is found a layer of much folded hard enamel, and below this is the less hard dentine. As the surface wears down by chewing the three materials, enamel, dentine and cement wear at different rates resulting in a very rough grinding surface well suited to break up tough, fibrous plant tissues. In addition, the teeth of these herbivores are tall (hypsodont) and even against heavy wear they last the lifetime of these animals. Click on the buttons, Diagram 1 or Diagram 2, to see the various arrangements. End of section. CARDe 2n p? Main Menuon mouseUp set scroll of card field 1 to 0 go to Card 2 end mouseUp0 8? Special Studies69v? Air Bladder and LungNt? Diagramon mouseUp go to card 104 end mouseUp"D r l ? Submenuon mouseUp set scroll of card field 1 to 0 go to Card 73 end mouseUp .DE  SPECIAL STUDIES: AIR BLADDED AND LUNGS. Comparing the swim bladders, air bladders and lungs in various living vertebrates a mor- phocline can be constructed revealing that these structures may be homologous. The polarity is given by the primitive condition in extinct Agnatha, such as the members of Ostracoderm phyla (A in diagram). The air bladder of Agnatha is the outgrowth of two small pouches from the ventral side of the esophagus. This becomes enlarged and ventrally fused in primitive lungfishes such as Polypterus (B). The structure is further enlarged and becomes fully functional lungs as in Protopterus a living lungfish (C), and in reptiles, birds and mammals (D). Evolution takes a different turn in the morphocline derived from primitive Actinoptery- gians (E). Here the pouches reach a dorsal position and act as a pair of balancing, hydrostatic organs. Only one of these pouches remains in Ceratodus, a fossil lungfish from the Triassic (F) in which the bladder is dorsally situated and is connected through a long duct to the ventral side of the esophagus. Both, the position of the bladder and it short connection are dorsally situated in living Holosteans such as Lepidosteus, a gar, and Amia, a bowfin (G). Yet another morphocline can be derived from the primitive Actinopterygians (E) where the dorsally situated single pouch is connected to the esophagus through a more and more dorsally placed duct as in primitive teleosts such as Erythrinus (H) and Sturgeons (I). In a more advanced teleost group the dorsally placed hydrostatic organ is completely separated from the esophagus and gas is produced in them through specialized cells (J). In summary, the major morphoclines in the developmen of air bladders, swim bladders, and lungs involve the following trends: 1. Enlargement of the pouches into bilateral respiratory organs or lungs (A-B-C-D) 2. Movement of the enlarged pouches into a dorsal position (A-B-E) 3. Development of a double function, respiration and hydrostatic organ in the line leading to lungfishes (E-F-G) 4. Changes leading to exclusively hydrostatic function with a reduction of connection between esophagus and swim bladder (E-H-I-J). End of section. @CARDfPn p? Main Menuon mouseUp set scroll of card field 1 to 0 go to Card 2 end mouseUp0 8? Special Studiesn ? Sub Menuon mouseUp set scroll of card field 1 to 0 go to Card 73 end mouseUp,9v? DentitionsNu? Diagramon mouseUp go to card 113 end mouseUp"H r L.#>? ) SPECIAL STUDIES: DENTITIONS Apart from the general structure of molars and their grinding surfaces, also the degree of differentiation of dentition reveals the way animals lived and provides us with characteristic and distinguishing features of major vertebrate groups. The peg-like teeth of fishes and of aquatic mammals, such as dolphins and toothed whales, is adapted to catch and hold prey in water, and then swollow it whole. Such an undifferentiated arrangement is called the homodont dentition. The similarity of simple peg-shaped teeth in widely different vertebrates is due to coadaptation to the same environment and to the same mode of life, giving examples of analogy. The semiheterodont dentition shows a slight degree of differentiation. Here at least some regions of the jaws have a little larger or smaller peg-shaped teeth. In the alligator, the region where the canine teeth would be in a more differentiated form, the teeth are somewhat larger. The third arrangement is the heterodont dentition where there is a clear differentiation of incisors, canines, premolars and molars. The dentition of canivorous mammals such as the fully differentiated teeth of a dog is a classical example. In certain mammals the heterodont dentition is modified. In carnivors one of the lower molars or premolars and the one above it in the upper jaw are enlarged and are provided with a sharp cutting edge. They act as a pair of scissors to cut meat. They are called the carnassials. In rodents the canine teeth are absent leaving a gap between the incisors and the first premolars. This gap is called the diastema. The incisors of rodents grow continuously and are kept the same length by constant chewing. The primate dentition is heterodont where the molars are low crowned (brachydont) and the canine teeth are somewhat reduced. This arrangement is characteristic to omnivorous diet. In humans the canines are further reduced to the same height as the other teeth around them. End of section.CARDg\2N p? Main Menuon mouseUp go to Card 2 end mouseUp0 8? Special StudiesN ? Sub Menuon mouseUp go to Card 73 end mouseUp*9v? 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