Name: _________________________________________________ Date: ________________ Period: _______
Biology: Building a Cladogram
The objective of this lab is to build a cladogram that shows the evolutionary relationship between some
“unknown species” based on the morphology (shape/structure) of their fossils.
A cladogram is a branching diagram used to show patterns of evolutionary relatedness. It begins with a single
shared trait, and branches off until all organisms are at the end of their own branch.
The principle of parsimony should be used to help create cladograms. This principle says…
o The simplest cladogram is most likely the correct one.
o It is more likely for a trait to evolve only once.
Procedure:
1) Examine the 8 fossils and construct a cladogram that shows the most likely relationship between
them.
2) Start with one common trait (they are all pointy) and begin to separate each creature until all have
reached an end branch.
Tips:
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According to the Principle of Parsimony it is more likely that a trait will evolve only once.
Therefore, you cannot use the same trait on two different branches.
Use a pencil (so you can erase)!
Unknown prehistoric fossils:
Analysis:
1. Examine fossils #6 and #8. According to your cladogram, what are the…
Traits in common:
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Traits that differ:
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2. According to your cladogram, which two species are most closely related? Why?
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3. According to your cladogram, which two species are the least closely related? Why?
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4. Why is one cladogram only considered a hypothesis?
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5. If these really were fossils of ancient organisms, what may have caused the evolution of traits that
appeared higher up on your cladogram?
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