Name:_________________________
Mod:_____
Date:_______
Evolution Lab: Comparative Anatomy
Introduction: The species of plants and animals living today are different from their ancestors of millions of years ago.
Much evidence has been accumulated to show that organisms change their form and characteristics as centuries passed,
the old species vanished and the new ones took their place.
Objectives:
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To learn about vestigial, homologous and analogous structures and how they lend evidence to the theory of
evolution
Determine the age of various rock layers and what representative organisms belong to each layer
Procedure:
Fossils:
A.
Look at the drawing of the rock layers. Determine which layer is the oldest and which is the youngest layer.
Analyze the species list below. Determine which rock layer they would appear in. Remember organisms started
out simple and have become more and more complex. (HINT: Layer A contains three organisms, B contains two,
C and D both contain one organism.)
B. Write the organisms in the appropriate rock layer.
Rock Layers:
Species List:
Bird, starfish, algae, early human, maple tree, horse, jellyfish
D:
C:
B:
A:
C.
Explain your reasoning for putting the organisms in the rock layers.____________________________________
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Homologous Structures: those structures that are fundamentally similar in structure and have the same evolutionary
origin but they have DIFFERENT functions. Examine the five structures in the diagram below. Color the humerus of each
organism the same color. (Hint: it is the large bone at the top of each structure) Color the other bones corresponding
colors to show that all the organisms have the same bone structure.
D)
Describe the FUNCTION of each set of bones:
Arm:______________________________________________________________________________________________
Lion Leg: :__________________________________________________________________________________________
Bat Wing: :_________________________________________________________________________________________
Bird Wing: :________________________________________________________________________________________
Whale Flipper: :____________________________________________________________________________________
Analogous Structures: structures that have the SAME function but different basic compositions and different
evolutionary origin but similar functions.
E) What function do they share? ____________________________________________________________________
F) How do the structures differ?_______________________________________________________________________
Vestigial Structures: structures that do not appear to have any function but which seem to be derived from useful
structures in ancestral forms of life. 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 snake’s leg bones are
examples of this phenomenon. Examine the diagrams of the cave fish and the minnow. These fish are related but the
cave fish is blind.
G) Explain why eyesight is not an important adaptation to life in a cave.
__________________________________________________________________________________________________
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H) Below is a list of human vestigial organs. Suggest a possible function for each and explain why the organism is now
vestigial.
“Wisdom” Teeth:___________________________________________________________________________________
Appendix:_________________________________________________________________________________________
Coccyx (fused tail bone) :_____________________________________________________________________________
Conclusion and Discussion:
1) Define the following and give an example of each:
a. Homologous Structure:__________________________________________________________________
_____________________________________________________________________________________
b. Analogous Structure:____________________________________________________________________
____________________________________________________________________________________
c. Vestigial Structure:_____________________________________________________________________
____________________________________________________________________________________
2) Explain the evolutionary relationship between the fin of a fish and the flipper of a whale.
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3) How can we account for the presence of such useless structures in the human body such as the appendix?
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4) Why might unrelated organisms evolve organs with similar structures?
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