Download Part I: Anatomical Homologies

Evidence of Common Ancestry
Biological Evolution and Classification
Part I: Anatomical Homologies
1.  What is a homologous structure, and what are some examples?
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2.  Describe the Cambrian explosion and its significance.
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3.  Humans are mammals, and mammals are defined by having a certain set of anatomical
homologies. Think about some familiar mammals. What are some homologous structures that
are shared by all mammals? List them.
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4.  How is the human forelimb similar to that of the other three mammals you examined?
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5.  Why does this suggest a distant, common ancestry to other vertebrates? Explain your answer.
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6.  Analyze the forelimbs you constructed and labeled. What similarities would you expect to find in
the forelimb of a reptile, such as a small gecko? Identify and explain.
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Evidence of Common Ancestry
Biological Evolution and Classification
Part II: Developmental Homologies
1.  What are developmental homologies, and how are they studied?
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2.  What is a chordate, and what do all chordates have in common? Explain.
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3.  List five familiar organisms that are in the phylum chordata.
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4.  What is a notochord and where is it found?
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5. 
Title, color, and label the diagram below.
TITLE:
6.  What do all chordates have in common during embryonic development?
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Evidence of Common Ancestry
Biological Evolution and Classification
Part III: Molecular Homologies
1.  Number of Differences in Cyt C Amino Acid Sequences
Human &
Chimpanzee
Rhesus
monkey
Cow, Pig,
Sheep
Kangaroo
Bullfrog
Human &
Chimpanzee
Rhesus
monkey
0
1
Cow, Pig,
Sheep
Kangaroo
Bullfrog
0
0
0
0
1.  Why are organisms with similar genetic sequences also likely to have similar protein
configurations? What is an example of this?
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2.  Cows, pigs, and sheep have identical amino acid sequences for Cyt c. What does this say
about their evolutionary relatedness? What other properties do these species have in
common?
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3.  Look at the table you completed above. If you were to sequence the amino acids for a
snapping turtle, which organism would you predict the sequences to most closely resemble?
Why?
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Evidence of Common Ancestry
Biological Evolution and Classification
Reflections and Conclusions
1.  What are the three main categories of homologies in living organisms? List them.
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2.  If a new single-celled organism was discovered in a lake and scientists determined it contained
DNA, would it share a common ancestry with other living species? Why or why not? Explain
your answer.
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3.  How do developmental homologies suggest common ancestry? Cite two specific animals that
show such a homology.
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4.  Explain how using homologies is a valid method for helping to determine relationships and
ancestry between organisms?
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5.  Use all of the following terms to develop a graphic organizer on a separate sheet of paper.
Terms: common ancestry, homologies, anatomical, developmental, molecular, forelimb, DNA,
chordates, vertebrates, fossil record, bacteria, plants, animals.
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