NAME: ______CLASS: ______

Evidence of Evolution - Lab 38

Background: Much evidence has been found to indicate that living things have evolved or changed gradually during their natural history. The study of fossils, as well as work in embryology, biochemistry, and comparative anatomy provides evidence for evolution. An organisms body structure is it’s basic body plan. Looking at the body structures of different organisms can be a clue as to how closely related those two organisms are. When scientists find similar structures in different organisms it is evidence that they may have inherited those structures from a common ancestor, and therefore, they may be more closely related.

In this lab you will learn about homologous, analogous, and vestigial structures. Homologous structures are structures which are formed in similar ways during embryonic development and share like arrangements, however they have somewhat different forms and functions. Analogous structures are those which share similar functions, yet they are very different in structure and form. Sometimes, as gradual changes occur in organisms over time, the function of some body structures becomes reduced or removed. Structures that no longer serve any function for the organism are called vestigial structures.

Part 1: Homologous Structures – (same structure-different function)

1.  Carefully examine the drawings of the bones shown in figure 1 on the next page. Each bone of the human arm is labeled and shaded with a different pattern. Color each part of the arm a different color.

2.  Next look at the whale’s flipper, crocodile and cat legs, and bird and bat wing bones. Notice that the structures are very similar. Find the coordinating bones and color them to match the colors you chose for the human arm bone.

3.  Once you have colored all the bones, describe the function of each of the structures that ware shown for the organism it belongs to.

Structure / Function
Human Arm
Whale Flipper
Crocodile Leg
Cat Leg
Bird Wing
Bat Wing

4.  Explain why these structures are considered Homologous Structures. ______

5. 

Part 2: Analogous Structures – (same function- different structure)

1.  Examine the butterfly wing and the bird wing shown below.

2.  What function do these structures share? ______

3.  How do these structures differ? ______

4.  Do birds and insects share any structural similarities that would suggest that they are closely related to each other? Explain ______

Part 3: Vestigial Structures

1.  The cave fish and the minnow shown below are related, but the cave fish is blind.

2.  Explain why eyesight is not an important adaptation for life in a cave. ______

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

______

4.  Below is a list of human vestigial structures. Suggest what a possible function for these structures may have been and explain why it is now vestigial.

Structure / Probable Original Function / Why is it Now Vestigial?
Appendix
Coccyx (tail bone)
Muscles that Move the Ears
Muscles that Make the Hair Stand Up
Little Toe
Wisdom Teeth

Analysis and Interpretations:

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

______

2.  Explain the evolutionary relationship between the fin of a fish and the flipper of a whale. ______

3.  Think of a structure (not listed in the table above) that you think is vestigial and explain why. ______