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EVIDENCES OF EVOLUTION LAB BACKGROUND: Evidence has been found to indicate that living things have changed gradually during their natural history. The studies of fossils as well as embryology, biochemistry, anatomy, geographic distribution and current observations of natural selection provide evidence for evolution. SECTION 1 : EVIDENCE FROM COMPARATIVE ANATOMY By comparing anatomical structures, evolutionary links can be established between groups of organisms. These comparisons include examining Homologous Structures, Analogous Structures and Vestigial Structures. a. HOMOLOGOUS STRUCTURES The structures in FIGURE 1 are formed in similar ways during embryonic development and share like arrangements: however, they have somewhat different forms and functions. They are called homologous structures. 1. Carefully examine the drawings of the bones in FIGURE 1. Look for similarities among the various animals. COLOR each part of the human arm a different color. Color all the bones of the wrist another color and the bones of the phalanges (fingers) yet another color. Then color the corresponding bone in each of the other animals the same color as those in the human bone. 2. In Table 1, describe the function of the phalanges (fingers) of each set of bones. FIGURE 1 TABLE 1 ANIMAL FUNCTION of PHALANGES Human Lion Horse Whale 1. Explain how homologous structures are evidence of an evolutionary relationship among species? b. ANALOGOUS STRUCTURES FIGURE 2 Some apparently unrelated animals have organs with similar function, yet are very different in structure and form. These structures are called analogous structures. Examine FIGURE 2 of the moth wing and the bat wing. Answer questions 3-5. 3. What function do the structures in FIGURE 2 share? 4. How do the structures in FIGURE 2 differ internally and externally? 5. Do bats and insects share any structural similarities that would suggest they are closely related? c. VESTIGIAL STRUCTURES Gradual changes have occurred through time that have in some cases reduced or removed the function of some body structures and organs. The penguin’s wings and the leg bones of snakes are examples of this phenomenon. Organs or structures that lost their function in the organism and become reduced in size (because of efficiency) are called vestigial structures. Human vestigial organs are well documented. The fish in FIGURE 3 are related, but the cave fish is blind. Think for a moment about how this lack of vision would affect the cave fish, then answer questions 6 - 9. FIGURE 3 6. Why is eyesight not an important adaptation to life in a cave? 7. Does the appearance of the cave fish and minnow suggest common ancestry? Why? 8. How do you think vestigal structures came about? 9. How do vestigal structures give evidence for evolutin? Read the list of human vestigial structures in Table 2. Complete Table 2 with suggestions for possible functions for each structure. TABLE 2 STRUCTURE Appendix Coccyx (tail bones) Muscles that move ears Muscles that make hair stand up (for warmth) Wisdom Teeth PROBABLE FUNCTION Possible raw meat digestion WHY VESTIGIAL? FIRE…. Started cooking meat Not needed for walking or running upright Reliance on vision Clothing Softer food, diet change, fire SECTION 2: EVIDENCE FROM COMPARATIVE EMBRYOLOGY Evolution occurs slowly. In most cases, it is not possible to observe evolution in progress. However, evidence of evolution can be found by observing the early stages of development in vertebrates. All vertebrate embryos start out similar in appearance. This similarity has led scientists to think that these organisms have a common ancestor. The diagrams below illustrate stages in the embryonic development of a fish, a pig, and a human. Study the diagram below and answer questions 10 and 11. 10. How does comparative embryology provide evidence of evolution? 11. As the embryos grow and develop, what happens to the appearance of the embryos? Section 3:EVIDENCE FROM COMPARATIVE BIOCHEMISTRY All living things are based on a universal genetic code of DNA. If organisms’ traits change over time and traits are determined by genes (made of DNA), then we can only assume that their DNA changes over time as well. Amino acid sequences of certain proteins can be used to determine how closely related different species are. If the amino acid sequences for a certain protein are very similar in two species, one can assume that those two species had a common ancestor. All 104 amino acids in the protein cytochrome c are identical in humans and chimpanzees. 1. Observe CHART 1 in which it shows how many of the amino acids in cytochrome c in other animals differ from those in humans and chimps. Answer questions 12 and 13. Animal Dog Dogfish shark Rattlesnake Rhesus monkey CHART 1 # of Amino Acid differences in Cytochrome C compared to humans 8 24 12 1 12. Which of the organisms would be most biochemically similar to humans: fish or pig? Why? 13. How does the information in CHART 1 support evolutionary theory? SECTION 4: EVIDENCE IN THE FOSSIL RECORD According to the geological law of superposition, older layers of sedimentary rock lay beneath younger layers. Scientists use this law to determine the order in which organisms appeared and disappeared in the fossil record. The law cannot be used to determine the absolute ages of rock layers. It can be used to determine the relative ages of rock layers by comparing their fossil records. Study FIGURE 5 containing diagrams that represent neighboring sedimentary rock formations, answer questions 14-16. FIGURE 5 14. In FIGURE 5, which layer is the oldest in each formation? 15. Are the two layers the same age? How could you tell? 16. Suppose fossils from Layer "C" of Formation 2 are the same fossils as those in Layer "D" in Formation 1. What could you say about the relative ages of all layers in both formations? SECTION 5: GEOGRAPHIC EVIDENCE OF EVOLUTION All organisms are adapted to their environment to a greater or lesser extent. If the abiotic (not living) and biotic (living) factors within a habitat are capable of supporting a particular species in one geographic area, then one might assume that the same species would be found in a similar habitat in a similar geographic area, as for instance in Africa and South America. This is not the case. Plant and animal species are distributed irregularly throughout the world. For example: Old World monkeys, which resemble humans and the great apes in anatomy and body functions, are found mostly in parts of Africa and Asia. Many spend as much or more time on the ground as they do in trees. New World monkeys, found in the Americas, are all tree dwellers, and many of them use their prehensile tails in traveling through forests. Examine the similarities & differences between the Old World and New World organisms shown below. Answer questions 17 and 18. Old World Africa: Old World Monkeys, apes, elephants, leopards, giraffes, hornbills, camels, Euphorbs (succlents) New World The Americas: New World Monkeys, cougars (aka Mountain Lions), jaguars, sloths, llamas, toucans, cacti 17. Compare and contrast one Old World orgnanism with a similar New World organism. What characteristics do they have in common? What are the differences? Why may that be? 18. How does their geographic location provide evidence for evolution? SECTION 6: EVIDENCE FROM OBSERVED NATURAL SELECTION Examples for the evidence for evolution often stems from direct observation of Natural Selection in the field and the laboratory. Scientists have observed and documented a multitude of events where Natural Selection can be seen in action. The most well known examples are antibiotic resistance in the medical field and the spread of pesticide resistant forms of plants and insects. One classic example of adaptation in response to selection pressure is the case of the peppered moth. The color of the moth has gone from light to dark to light again over the course of a few hundred years due to the appearance and later disappearance of pollution from the Industrial Revolution in England. Originally, the vast majority of peppered moths had light coloration, which effectively camouflaged them against the light-coloured trees and lichens which they rested upon. However, because of widespread pollution during the Industrial Revolution in England, many of the lichens died out, and the trees that peppered moths rested on became blackened by soot, causing most of the lightcolored moths to die from predation. At the same time, the dark-colored moths flourished because of their ability to hide on the darkened trees. With improved pollution laws, the soot has been controlled, and the light colored moths are once again dominant. Peppered Moths prior to the Industrial Revolution Peppered Moths during the Industrial Revolution 19. How does the Peppered Moth observation of natural selection support the theory of evolution? TABLE 3: EVIDENCES OF EVOLUTION COMPLETE THE CHART by checking the kind of evidence described. KIND OF EVIDENCE Evidence COMPARATIVE… STURCTURAL ANATOMY Embryology Homologous E 20. A modified structure seen among different groups of descendants 21. In the earliest stages of development, a tail and gill slits can be seen in fish, birds, rabbits, and mammals. 22. The continuous discovery new antibiotic resistant bacteria 23. The forelimbs of flightless birds 24. Changes in the coloration of insects within only a few generations 25. Similarities between the Old World Monkeys and the apes. 26. A body structure reduced in function but may have been used in an ancestor 27. The beaks on the finches of the various Galapagos Islands 28. DNA and RNA comparisons may lead to evolutionary trees 29. Bird and butterfly wings have same function but different structures. 30. Examples of forelimbs of bats, penguins, lizards, and monkeys 31. Give your own example of how the Fossil Record can be an evidence of evolution Analogous Vestigial Biochemistry Geographic Distribution Observed Natural Selection TABLE 3: EVIDENCES OF EVOLUTION COMPLETE THE CHART by checking the kind of evidence described. KIND OF EVIDENCE Evidence COMPARATIVE… STURCTURAL ANATOMY Embryology Homologous E 20. A modified structure seen among different groups of descendants 21. In the earliest stages of development, a tail and gill slits can be seen in fish, birds, rabbits, and mammals. 22. The continuous discovery new antibiotic resistant bacteria 23. The forelimbs of flightless birds 24. Changes in the coloration of insects within only a few generations 25. Similarities between the Old World Monkeys and the apes. 26. A body structure reduced in function but may have been used in an ancestor 27. The beaks on the finches of the various Galapagos Islands 28. DNA and RNA comparisons may lead to evolutionary trees 29. Bird and butterfly wings have same function but different structures. 30. Examples of forelimbs of bats, penguins, lizards, and monkeys 31. Give your own example of how the Fossil Record can be an evidence of evolution Analogous Vestigial Biochemistry Geographic Distribution Observed Natural Selection