Evolutionary Relationships 2009
Name: _____________________ Period: ____
Purpose/Objectives:
During this activity, you will use different lines of evidence (body
structure and molecular structure) to infer the evolutionary relationship among
several animals. You will then construct a phylogenetic tree that illustrates
how these species relate to each other based on similarities in morphology and
DNA sequence.
By the end of this exercise, you should be able to:
 State evidence that supports the theory of evolution.
 Explain how scientists infer evolutionary relationships among species.
 Explain how a branching (phylogenetic) tree diagram shows
evolutionary relationships.
Background:
Fossils, embryos, and body structures all provide evidence that
organisms have changed over time. These same lines of evidence can also be
combined to make inferences about evolutionary relationships among species.
Recently, molecular evidence (DNA and proteins) has been used to confirm
many of the evolutionary relationships (called phylogeny) determined by
fossil, embryo, and body structure (morphology) evidence.
The comparison of structures of different organisms is called
comparative anatomy. Homologous structures are similar structures that
related species have inherited from a common ancestor. Organisms with
homologous structures might have evolved from the same ancestor. The more
similar these structures are, the more closely related the organisms probably
are. The same is true for molecular evidence. If two species have similar DNA
and proteins, they probably evolved from the same ancestor, and the more
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Minority Science Programs – School of Biological Sciences – University of California, Irvine
Evolutionary Relationships 2009
similar the DNA or protein sequence is, the more closely related the two
organisms most likely are.
Vocabulary:
Evolution
Phylogeny
Morphology
Comparative Anatomy
Homologous Structures
Materials:
 Images of several animal species
 DNA sequences
Methods/Procedure:
EVIDENCE FROM MORPHOLOGY
1. Compare images of several animal species and record your observations
in TABLE 1.
EVIDENCE FROM DNA SEQUENCES
1. Align the DNA segments from two animal species, and count the
number of differences.
2. For each pair of species compared, write the number of differences in the
proper space on TABLE 2.
3. Repeat steps 1-2 until you have compared all the species.
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Minority Science Programs – School of Biological Sciences – University of California, Irvine
Evolutionary Relationships 2009
Name: _____________________ Period: ____
Results:
TABLE 1
Body Structure Observations
Brown Bear
Polar Bear
Great Panda
Red Panda
Raccoon
TABLE 2
Polar Bear Great Panda Red Panda Raccoon
Brown Bear
Polar Bear
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Minority Science Programs – School of Biological Sciences – University of California, Irvine
Evolutionary Relationships 2009
Great Panda
Red Panda
Raccoon
Questions:
1. Which animals would you group together based on morphology? Why?
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
2. According to your DNA sequence comparison, which 2 species appear to be the
most closely related?
__________________________________________________________________
3. Label the phylogenetic tree below according to similarities in DNA
sequence.
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Minority Science Programs – School of Biological Sciences – University of California, Irvine
Evolutionary Relationships 2009
4. What can body structures tell you about how species might be related?
__________________________________________________________________
5. What does DNA tell you about how similar two species are?
__________________________________________________________________
Great
Panda
GTTAGTATAA
Red
Panda
GTCGATGAGA
Polar
Bear
GCTCTCATAA
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Minority Science Programs – School of Biological Sciences – University of California, Irvine
Evolutionary Relationships 2009
Brown
Bear
GATCTCATAA
Raccoon
GTCGATTCGA
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Minority Science Programs – School of Biological Sciences – University of California, Irvine