Evidence of Evolution

Evidence of Evolution

Evidence has been found to indicate that living things have changed gradually during their natural history. The study of fossils, as well as embryology, molecular biology, and comparative anatomy provide evidence for evolution.

Part 1: Comparative Anatomy

Comparative Anatomy is the branch of biology that concentrates on the similarities and difference in anatomical features of different species. By comparing the anatomy of different organisms, scientists have noticed many structural

similarities among organisms. A pattern of similar characteristics may suggest evolutionary relatedness. Continue below to learn about homologous structures, analogous structures and vestigial structures.

Homologous structures:

1. Carefully examine the drawings of bones shown on the next page. Look for similarities among the various animals.

a. COLOR each part of the human arm a different color using the following key:

Humerus: Yellow Carpals: Red Radius: Blue Ulna: green Metacarpals: Purple Phalanges: Orange

b. In Table 1 (On the Answer sheet) describe the function of each set of bones and answer the questions that follow.

Analogous structures:

2. Examine the butterfly wing and the bird wing. Answer the questions for this section on the answer sheet.

Vestigial Structures:

Gradual changes have occurred through time that have in some cases reduce or removed the function of some body structures and organs. The penguin’s wings and the leg ones of snakes and whales are examples of this phenomenon.

3. The cave fish and minnow are related, but the cave fish is blind. Answer questions 8-9 on the answer sheet.

4. Read the list of human vestigial structures in Table #2. Suggest a possible function for each structure and explain

why it became vestigial.

Part 2: Embryology

Embryology is the branch of developmental biology that focuses on the early development of organisms before they are born or hatched. During this pre-birth or pre-hatching stage, scientists call the developing organisms embryos.

When the scientists compare the developing embryos of organisms as diverse as fish, amphibians, reptiles, birds and mammals, they find that the embryos of these vertebrate animals (animals that have backbones) resemble each other.

1. Get the packet of embryo drawings from your teacher. Study the individual drawings of embryos. Try to arrange all the embryonic stages in a developmental order for each animal. When you have finished, your arrangement should show 3 stages of embryonic development for a fish, a frog, a chicken, a calf and a human.

Show your teacher for a stamp.

2. Answer the questions on your answer sheet for this section

Part 3: Molecular Biology

Molecular biologists look at life from the level of DNA, RNA and proteins. Fossils, anatomical structures and embryo development all provide clues that reflect what took place at the molecular level. DNA and proteins (genes and the products of genes) provide powerful evidence for decent with modification. As DNA changes over time, the proteins produced also change. The result: many organisms have similar, but not identical versions of a given protein

1. Get the packet of organism pictures from your teacher. Based only on their anatomy, rank gorillas, bears, chimpanzees, gibbons, monkeys, shrews and mice from most common ancestor with humans (closely related) to least recent common ancestor with humans (not closely related). Write your predicted order on your answer sheet (#14).

2. Answer question 15 and show your teacher to get a stamp.

3. Compare the amino acid sequences in hemoglobin between these organisms. Use a dry erase marker to highlight the differences. Record the number of differences in Data Table 3 on your answer sheet.

4. Answer the questions on your answer sheet for this section.

Part 1: Comparative Anatomy Homologous Structures

1. COLOR CODE the bones according to instructions:

2. Use the following word bank to match each animal’s bones above with their function:

Flying Flying Swimming, walking, Running & Standing

Walking, Running, & Standing Swimming Grasping & balance Data Table 1:

Animal Function

Human Whale Cat Bat Bird Crocodile

3. Are the bones arranged in a similar way in each animal? ________________

These structures are formed in similar ways during embryonic development and share like arrangements. However, they have somewhat different forms and functions. They’re called HOMOLOGOUS STRUCTURES.

4. Explain why homologous structures are evidence of evolutionary relationships.

Analogous structures: Butterfly wing and Bird wing:

5. What function do these structures share?

6. How are the structures different?

7. Do birds and insects share any structural (the way they are built) similarities that would suggest they are closely related?

Some apparently unrelated animals have organs with similar functions, yet are very different in structure and form. These structures are called ANALAGOUS STRUCTURES.

Vestigial Structures

8. Explain why eyesight is not an important adaptation to life in a cave.

9. Does the appearance of the cave fish and minnow suggest common ancestry? Why?

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.

10. Read the list of human vestigial structures sown below. Suggest a possible function for each structure and explain why it became vestigial. (HINT: think of an animal that still has functioning structures – what are these structures used for in other animals?)

Table 2:

Structure Probable function Why vestigial?

Pinky toe Help climbing and swinging on branches Not used for those functions and has no use in balance

Coccyx (tail bones)

Muscles that move ears

Muscles that make hair stand up

Part 2: Embryology

11. Look at the embryos in their earliest stages. Describe patterns you see. What physical similarities exist between each of the embryos?

12. Do you think these similarities are evidence of a common ancestor? Explain your answer. (Consider whether you expect related organisms to look similar or not. Would you also expect them to go through similar stages of development? Consider later stages of development. Do the more closely related organisms look more or less similar?)

13. Which organism would be most related to humans? Explain your answer.

Part 3: Molecular Biology

14. Based only on anatomy, I predict the following order:

Most closely related to humans: _______________________, ____________________, _________________________, _________________________, __________________________, __________________________, ________________________, __________________________, least closely related to humans.

15. Hemoglobin from two species is compared. On the long protein chains, there are three locations where the amino acids are different. Would you state that these two organisms are closely related or distantly related? Explain your prediction.

16. Does the data support the rankings you made in question 14? If not, how would you explain any differences?

17. In terms of descent, what does it mean to say that humans are more closely related to gorillas than monkeys?

Table 3:

Mammal Number of differences in hemoglobin Bear

Chimpanzee

Gibbon

Gorilla

Monkey

Mouse

Shrew

Molecular Biology organism sort:

Procedure

Comparing Amino Acid Sequences in Hemoglobin

Hemoglobin is the molecule in blood that carries oxygen. This complex molecule contains four protein chains. Figure 1 shows the amino acid sequence for one of those chains in eight mammals. Each letter stands for a different amino acid. Each column is a location on the protein chain. NOTE : Locations where the amino acids are identical in all eight mammals are not shown.

1 . Use the row labeled Human as your control. Compare the sequence for the bear to the sequence for humans. When you find a difference in the bear sequence, highlight it.

2. Repeat Step 1 for each of the other mammals. Be sure to compare each sequence to the sequence for humans.

Figure 1 Comparison of amino acid sequences in hemoglobin from eight mammals

4 5 6 9 10 12 13 20 25 33 41 43 50 51 52

Human T P E S A T A V G V F E T P D

Bear T G E S L T G V G V F D S A D

Chimpanzee T P E S A T A V G V F E T P D

Gibbon T P E S A T A V G V F E T P D

Gorilla T P E S A T A V G V F E T P D

Monkey T P E N A T T V G L F E S P D

Mouse T D A A A S C S G V Y D S A S

Shrew S G E A C T G E A V F D S A S

54 56 58 68 69 70 71 72 73 75 76 77 80 87 104

Human V G P L G A F S D L A H N T R

Bear I N P L N S F S D L K N N K K

Chimpanzee V G P L G A F S D L A H N T R

Gibbon V G P L G A F S D L A H N Q R

Gorilla V G P L G A F S D L A H N T K

Monkey V G P L G A F S D L N H N Q K

Mouse I G A I T A F N D L N H S S R

Shrew V G P L H S L G E V A N N K R

109 110 112 115 116 117 118 121 125 126 130 139

Human V L C A H H F E P V Y N

Bear V L C A H H F E Q V Y N

Chimpanzee V L C A H H F E P V Y N

Gibbon V L C A H H F E Q V Y N

Gorilla V L C A H H F E P V Y N

Monkey V L C A H H F E Q V Y N

Mouse M I I G H H L D A A F T

Shrew V L V A S K F E P V F N