Evolutionary Relationships 2009
Name: TEACHER NOTES 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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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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Evolutionary Relationships 2009
Name: _____________________ Period: ____
Results:
TABLE 1
Body Structure Observations (examples)
Brown Bear
Large body, rounded ears, small tail, dark fur, long snout
Polar Bear
Similar to above with light fur and shorter snout
Great Panda
Medium body, short fur, round ears, specific coloration
Red Panda
Small body, pointed ears, long & ringed tail, red fur
Raccoon
Similar to above with gray color, dark eye spots
TABLE 2
Brown Bear
3
Polar Bear Great Panda Red Panda Raccoon
1
4
8
8
Polar Bear
4
8
8
Minority Science Programs – School of Biological Sciences – University of California, Irvine
Evolutionary Relationships 2009
Great Panda
6
6
Red Panda
2
Raccoon
Questions:
1. Which animals would you group together based on morphology? Why?
Raccoon and Read Panda- they are both small-bodied, have long & striped
tails, and pointed ears. Polar Bear and Brown Bear- they both have very
large bodies, small tails, long neck and snout, and solid coloring.
2. According to your DNA sequence comparison, which 2 species appear to be the
most closely related?
Polar Bear and Brown Bear (then Red Panda and Raccoon)
3. Label the phylogenetic tree below according to similarities in DNA
sequence.
Great
Panda
4
Polar
Bear
Brown
Bear
Red
Panda
Raccoon
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?
Similar body structures suggest organisms may share a common ancestor.
(i.e. They may be related.)
5. What does DNA tell you about how similar two species are?
The more similar the DNA is, the more closely related the organisms
probably 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
6
Minority Science Programs – School of Biological Sciences – University of California, Irvine