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EVIDENCE OF EVOLUTION-COMPARATIVE ANATOMY INTRODUCTION: Evidence has been found to indicate that living things have changed gradually during their natural history. The study of fossils as well as embryology, biochemistry, and comparative anatomy provides evidence for evolution. OBJECTIVE: In this lab activity you will learn about homologous, analogous, vestigial structures, fossils, embryology and biochemistry and their significance in evolution theory. MATERIALS: Map Pencils PROCEDURES: HOMOLOGOUS STRUCTURES 1. Carefully examine the drawings of the bones. Look for similarities among the various animals. 2. Color the homologous bones according to the color scheme below: Green = humerus Red = radius Blue = ulna Yellow = metacarpals Purple = phlanges 3. Then color the corresponding bone in each of the other animals the same color as the human bone. humerus radius ulna metacarpals phalanges Human Horse Cat Bat Bird Whale 2. Describe the function of each set of bones below: ANIMAL FUNCTION Human Picking up objects, carrying things Horse Walking, running Cat Walking, running, scratching, digging, hunting Bat Flying, clinging to food/edges Bird Flying Whale Swimming 3. Are the bones arranged in a similar way in each animal? _Yes, same order_______ These structures 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. ANALOGOUS STRUCTURES Examine the butterfly wing and the bat wing. butterfly bat 4. What function do these structures share? _Both designed for flight____ 5. How do the structures differ? Bat wings have bones, butterfly wings don’t have bones___ 6. Do bats and insects share any structural similarities that would suggest they are closely related? They both have wings. Some apparently unrelated animals have organs with similar function, yet are very different in structure and form. These structures are called analogous structures. 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. The term "vestigial" is used in the sense of an organ no longer or not being used as it is in most other animals. Whales have a pelvis and a femur. In most animals the pelvic bones are needed in order to be able to move the lower or rear set of limbs for the purpose of locomotion. 7. Explain why the presence of a pelvis is not an important adaptation to life in the ocean. Whales do not walk, they swim. If they don’t have legs to walk, they don’t need a pelvis 8. Does the appearance a pelvis in a whale suggest common ancestry to land animals? Explain. Yes, it shows that they had an ancestor that must have had legs and walked on land 9. Read the list of human vestigial structures in Table 2 Suggest a possible function for each structure and explain why it became vestigial. Remember, these organs would have been functional in our ancestors. Think about why our ancestors would have needed this organ and then think about why modern humans (through evolution) would no longer need this organ. Other animals still have these organs. Think about why they have them/how they use them…this might help understand why our ancestors needed them. STRUCTURE PROBABLE FUNCTION WHY VESTIGIAL? Appendix Possible raw meat digestion FIRE…. Started cooking meat Coccyx (tail bones) Tail used to climb/balance in trees Hunting/listening for predators/communication We live on the ground and don’t have tails. We can move head side to side/ears are on side of head/ speech developed. Speech developed Muscles that move ears Muscles that make hair stand up Communication/threat Little toe Wider feet for balance/climbing trees Larger chewing surface for tougher/raw food Wisdom Teeth Ground dwelling. We don’t travel by foot as much Started cooking food. Embryology Can you tell a chicken from a fish? How about a human from a pig? Sure you can, you say. Chickens have wings, fish have fins, humans have arms and pigs have hoofs. But what about when they are just beginning to develop? 10. Look at the embryology cards. They represent three developmental stages of five different animals. They have been all mixed up -- see if you can tell what's what. 11. Arrange the squares and see if you can correctly match the embryos with the animals, placing them in order from earliest to latest stages of development. 12. Fill in the chart with the number that is on the card. FISH CHICK PIG CALF HUMAN Stage 1 8 2 4 10 3 Stage 2 1 7 15 6 11 Stage 3 14 9 13 12 5 13. Write an explanation of why you ordered the drawings the way you did. Answers will vary. Looked at and compared structures. 14. What are some similarities among the drawings? Answers will vary. All have tails and gill pouches until stage 3. All very similar in development during stage 1. 15. What are some differences among the drawings? Answers will vary. Fish don’t have ear holes. Shapes of head begin to differ during stage 2 16. What patterns (among all 5 species) do you see as you go from stage 1 to stage 3? Answers will vary. All are very similar during stage 1. During stage 2, limbs appear and heads begin to take shape. It is still hard to differentiate between mammals. During stage 3, it is apparent which organism is which. Amino Acid Sequencing PURPOSE: To analyze amino acid sequences as a guide for relationships and common ancestry. Scientists can examine the amino acid sequences of particular protein molecules found in vertebrates to determine the degree of similarity between vertebrate species. Even organisms that appear to have few physical similarities may have similar sequences of amino acids in their proteins and be closely related through evolution. Scientists believe that the greater the similarity in the amino acid sequences of two organisms, the more closely related they are in an evolutionary sense. Part A: Cytochrome-c is a protein found in the mitochondria that is used in cellular respiration. This protein consists of a chain of 104 amino acids. The chart below shows the amino acid sequence of nine vertebrates. The letters identify the name of the amino acid. Animal Horse Chicken Tuna Frog Human Shark Turtle Monkey Rabbit A B C D E F G Amino Acid Sequences in Cytochrome-c H I J K L M N O gln gln gln gln gln gln gln gln gln pro glu glu ala pro gln glu pro val phe phe phe phe tyr phe phe tyr phe thr ser ser ser ser ser ser ser ser thr thr thr thr thr thr thr thr thr ala asp asp asp ala asp glu ala asp lys lys lys lys lys lys lys lys lys asn asn ser asn asn ser asn asn asn lys lys lys lys lys lys lys lys lys thr thr val thr ile thr thr thr thr lys gly asn gly gly gln gly gly gly glu glu asn glu glu gln glu glu glu glu asp asp asp asp glu asp asp asp thr thr thr thr thr thr thr thr thr leu leu leu leu leu leu leu leu leu P Q R S T U V met met met met met arg met met met glu glu glu glu glu ile glu glu glu lys lys ser ser lys lys asp lys lys ala ala ala ala ala thr ala ala ala thr thr thr cys thr ala thr thr thr asn ser ser ser asn ala ser asn asn glu lys -lys glu ser lys glu glu DATA Compare the amino acid sequence of human cytochrome-c with that of the other eight vertebrates. For each vertebrate, count the number of amino acids that differ from those in the human and write the number in the chart to the right. TABLE 1 Number of Amino Acid Differences from Human Cytochrome-c Number Species Differences Human 0 Horse 5 Chicken 6 Tuna 10 Frog 8 Shark 14 Turtle 7 Monkey 1 Rabbit 4 DATA ANALYSIS 1. Based on the data, list the order in which these vertebrates are related to humans. Place the vertebrates more similar to humans in sequence at from the top. TABLE 2 Similarity Ranking Animal AA Difference Human 0 Monkey 1 Rabbit 4 Horse 5 Chicken 6 Turtle 7 Frog 8 Tuna 10 Shark 14 2. Using the amino acid differences, which organism is most closely related to humans? Monkey 3. Using the amino acid differences, which organism is least closely related to humans? Shark 4. A cladogram is a tree-like diagram showing evolutionary relationships. Use the data from Table 2 and fill in the cladogram to show the relationship of these animals compared to the human. Label the location on the cladogram where you would place the common ancestor to all of these animals. 0 5 10 15 Number of amino acid differences from human Cytochrome-c 5. In the table you completed above, the number listed for the chicken and horse as compared to the human differs by only one. Compare the differences in amino acid sequences between the horse and the chicken. The difference is 7 . Considering both sets of data, can you conclude from this that the horse and the chicken are closely related? _No_ Why or why not? _______________________________________ There are 7 differences between them while there are only 5 between a horse and human. CONCLUSION: Summarize the concept of amino acid comparisons as they would indicate the possibility/closeness of a common ancestor. The less differences, the more related. The more differences, the less related. Fossil Evidence : The fossil record contains many well-documented examples of the transition from one species into another, as well as the origin of new physical features. Evidence from the fossil record is unique, because it provides a time perspective for understanding the evolution of life on Earth. This perspective is not available from other branches of science or in the other databases that support the study of evolution. During the 1990s our understanding of whale evolution made a quantum jump. In 1997, Gingerich and Uhen noted that whales (cetaceans) "... have a fossil record that provides remarkably complete evidence of one of life's great evolutionary adaptive radiations: transformation of a land mammal ancestor into a diversity of descendant sea creatures." The trail of whale evolution begins in Paleocene time, about 55 mya, with a group of even-toed, hoofed, trotting, scavenging carnivorous mammals called mesonychians. The first whales (pakicetids) are known from lower Eocene rocks, that formed about 50 mya; the pakicetids are so similar to mesonychians that some were misidentified as belonging to that group. However, the teeth of pakicetids are more like those of whales from middle Eocene rocks, about 45 mya, than they are like the teeth of mesonychians. Pakicetids are found in nonmarine rocks and it is not clear how aquatic they were. In 1994, Ambulocetus natans, whose name means "walking whale that swims," was described from middle Eocene rocks of Pakistan. This species provides fossil evidence of the origin of aquatic locomotion in whales. Ambulocetus preserves large forelimbs and hind limbs with large hands and feet, and the toes have hooves as in mesonychians. Ambulocetus is regarded as having webbing between the toes and it could walk on land as well as swim; thus, it lived both in and out of the water. From late Eocene time onward, evolution in whales shows reduction of the hind-limbs, modification of the forelimbs and hands into flippers for steering, development of a massive tail, etc.; all of these changes are modifications for the powerful swimming of modern whales. The fossil Rodhocetus from the upper Eocene rocks, about 46 mya, of Pakistan already shows some of these modifications. 1. Cut out the strips of “whales in the making” and arrange them in the correct order showing the evolution of the modern whale. Glue them onto another sheet of paper in the correct order (oldest at the bottom of the page and youngest at the top of the page).