Labs 27-30 Review Sheet Answer Key
Evolution
Vocabulary: Match the following words with their definition.
Evolution
Common descent
Vestigial structure
Slow process of change in organisms over long period of time
a group of organisms share a most recent common ancestor
a feature that was an adaptation for the organism's ancestor, but that evolved to be
non-functional because the organism's environment changed.
Divergent evolution
The process by which an interbreeding population or species diverges into two or
more descendant species, resulting in once similar or related species becoming less
and less alike.
Convergent evolution A kind of evolution wherein organisms evolve structures that have similar
(analogous) structures or functions in spite of their evolutionary ancestors being very
dissimilar or unrelated.
Natural selection
A process in nature in which organisms possessing certain characteristics are better
adjusted to an environment, therefore survive, reproduce, and increase the frequency
of that adapted characteristic.
Genetic drift
The process of change in a small population due to chance or random resulting in
changes in allele frequencies over time.
Mutation
A change in DNA caused by exposure to ultraviolet light, chemicals or even viruses.
It can also be the result of an error during meiosis or mitosis. It is the source of
variation for evolution.
Migration
The movement of organisms from one area to another. During gene flow it results in
increasing the variation within populations and decreasing the variation between
populations.
Selective pressure
Reduces reproductive success in a proportion of a population that do not have
adaptive traits
Speciation
The process in which new species evolve usually as a result of isolation from the main
population.
Gene flow
Sexual selection
Adaptation
Transfer of alleles from one population to another through migration of individuals.
A type of natural selection arising through preference by one sex for certain
characteristics in individuals of the other sex.
a change or the process of change by which an organism or species becomes better
suited to its environment
Lab 27: Phylogenetic Trees
1. An evolutionary tree shows the evolutionary relationships among various species that are believed to
have a common ancestor. This tree shows the evolution of vertebrate animals.
a.
b.
c.
d.
Which letter above is the common ancestor to all the vertebrate animals?A
Which letter above is the common ancestor for birds and dinosaurs?E
Which of the following are the most closely related? Birds and Dinosaurs
In the diagram above, which strand is an example of rapid diversification? D because many
organisms form in an evolutionarily quick timeframe
e. In the diagram above, which strand is an example of evolutionary stasis? Because there is no
change in Hagfishes or Lampreys for millions of years.
2. Mammalian milk contains antibodies that are produced by the mother’s immune system and passed
to offspring during feeding. Mammalian milk also contains a sugar (lactose) and may contain proteins
(protein A, protein B, and casein), as indicated in the table.
Character Cat
Cow
Horse
Human
Lactose
+
+
+
+
Protein A +
–
–
+
Protein B
–
+
+
–
Casein
–
+
+
–
+ indicates the presence of the character, and –
indicates the absence of the character
Pig
+
–
+
+
Using the data in the table, construct a phylogenetic tree on the template provided to indicate the most
likely evolutionary relationships among the different mammals. Determine where each of the
characters most likely arose in the evolutionary process.
Cat
Cow
Horse
Human
Pig
D or E
A, B or C
A, B or C
E or D
A, B or C
Lactose
Protein A
Protein B
Casein
4
3
1 or 2
1 or 2
The chart is correct if
you have the Cow,
Horse, and Pig on the
left side of the chart and
the Cat and Human on
the right. It doesn’t
matter the exact
location.
The chart is correct if you
have Protein B and Casein
under the Cow, Horse,
and Pig side of the chart.
It doesn’t matter which
number (1 or 2) that you
choose.
3. Give an example of divergent evolution. Give an example of convergent evolution.
Divergent Evolution: a flock of bird in migration gets divided as half of them settled to a new island while the
other half continued migrating to a farther land. Over time, the two groups become more adapted by
developing new characteristics to enable them to survive to their new habitats. Thus, they become a different
species to their ancestors and what was once one species has diverged into two.
Convergent Evolution: the wings of bats, birds, and insects. Each has evolved a similar body plan that allows
them to fly but their common ancestor did not have wings.
4. Give an example of gene flow
a small population of beetles infested some packing material in Asia and that material was transported to the
United States, the same species of beetles in the US now has access to genes from beetles in Asia.
Lab 28: Evidence for MacroEvolution
5. The diagram below represents a section of undisturbed layers of sedimentary rock in New York State
and shows the location of fossils of several closely related species.
a. Which species is the oldest? Species C because it is in the lowest sedimentary rock level.
b. How can you determine the specific age of species A? Scientists can use the half-life of
radioisotopes to determine the exact age of the fossils. They use carbon 14 dating if the rock
layer is less than 50,000 years or Uranium 238 if it is older.
c. What is the difference in relative dating and absolute dating? Relative dating is the science of
determining the relative order of past events, without necessarily determining their absolute
age. It says that younger rocks are found on top of older rocks.
Absolute dating uses certain elements that are radioactive, meaning that they break down over
time. Scientists know the time it takes for these elements to break down. Most absolute dating
is done by measuring radioactive Carbon 14 and Uranium 238.
d. Is a or b above an example of relative dating? Question a. Because you are determining the
answer by location in the layers and not isotope half-lives.
e. Describe three other pieces of evidences of speciation that would support the hypothesis that
species C evolved into B and A.
 Comparative Embryology- We can determine evolutionary relationships based on
characteristics that are present in embryos that are not present in adults. If Species B
and A had the same embryological characteristics that species C did, it would be
evidence that they might have shared that common ancestor.
 Comparative BioChemistry- we can determine evolutionary relationships based on
similarities in DNA or proteins. Often proteins are used more often than DNA sequences
because they are more general (remember more than one codon codes for an amino
acid). If Species A and B had similarities in a specific DNA sequence that was found in
species C, it would be evidence that they might have shared that common ancestor.
 Anatomy- We can determine evolutionary relationships based on similarities that are
found in homologous structures. This would include vestigial structures as well. If A and
B had a vestigial structure that appeared to have a function in species C then it would be
evidence that they might have shared that common ancestor.
6. Why do you think that organisms with fewer shared anatomical traits also have more amino acid
differences?
Both of these are evidence of relationships. The longer ago two organisms shared a common ancestor
the more differences you would expect in their anatomy and DNA.
7. Neurospora (bread mold) and Saccharomycetes (bakers yeast) are both in the Kingdom fungi and have
different amino acid sequences for cytochrome C. Chickens and turkeys are both birds in the Kingdom
Animal, Phylum Chordata, and Class Aves.
a. What can you say about the inferred evolutionary relationships between the two birds compared
to the relationship between the two fungi? Explain your reasoning.
Birds are more closely related than the two fungi because they share the exact same
cytochrome C protein. Although Neurospora and Saccharomycetes are two fungi they have
many differences in their cytochrome C and therefore are less closely related.
b. Which pair would share more DNA nucleotides in their cytochrome C gene?
Turkey and chickens.
Lab 29: Sexual Selection
8. When evolutionary biologist John Endler began studying Trindad’s wild guppies in the 1970s, he was
struck by the wide variation among guppies from different streams, even among guppies living in
different parts of the same stream. Males from one pool sported vivid blue and orange splotches along
their sides, while those further downstream carried only a modest splash of color near their tails.
Endler also observed differences in the distribution of guppy predators, and in the color and size of
gravel in different stream locations.
a. Male guppies are often brightly colored, while females are always drab. How would you
explain this difference between males and females within this species?
Sexual selection causes males to become more and more brightly colored because females choose
males that are brightly colored. More of their genes get passed to the next generation causing their
offspring to be brightly colored. Females are drab because they need to be able to hide from
predators. Those that are able to hide can take care of more offspring and pass their traits to the
next generation.
b. If being flashy attracts predators, why are male guppies so colorful?
Sexual selection allows female guppies to judge the quality of males’ genes by his ability to be
attractive to predators but still survive in the environment. Since females choose flashy males then
these traits get passed to the next generation.
c. Selective pressures are environmental forces that result in the survival of only certain
organisms with characteristics that provide resistance. What two selective pressures did this
experiment consider?
Sexual selection (ability to get sex) and natural selection (ability to hide from predators).
Lab 30: Genetic Drift verses Natural Selection
9. An enterprising farmer planted a grape arbor (similar to the
purple paper in Lab 30) next to a blueberry patch (blue paper) and
cranberry bogs (red paper). Lamarkia skittlia migrated from the
patch and bog to the grape arbor.
a. Use the six parts of Darwin’s Theory on Evolution by
Natural Selection to explain what would happen to purple
Lamarkia skittlia in the grape arbor.
There is variation in color of the insects and that variation is inherited. During the spring there
are many insects that are produced and not all can survive. Those insects that can blend into
their environment are able to live longer and reproduce more. Therefore the population will
change over time and with more purple alleles present in the population.
b. Which phenotype(s) would be most likely to escape the predator in the grape arbor? purple
c. Which phenotype(s) would be most likely to escape the predator in the blueberry patch? blue
d. Which phenotype(s) would be most likely to escape the predator in the cranberry bog? red
10. Now assume a geographic change occurs (like the Colorado River cutting through the Grand Canyon)
in the area and the population of Lamarkia skittlia is separated into 2 groups.
a. Explain how the allele frequency would be different in these two new groups in comparison to
the original population.
Since it is a random separation of the populations, genetic drift would cause the allele
frequencies in these populations to be different. If the environment is different on either side
of the river then the populations would evolve by natural selection or become extinct.
b. What type of evolution is occurring in these populations?
Genetic drift is the separation of the alleles and natural selection is the change in the
populations through difference selective pressures.