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NAME: ________________________________ PID: ______________ Group Name: _________________
BioSci 110, Fall 08
Exam 3
For questions 1 and 2 use the phylogeny to the
right.
1. With what group of species do rodents share
the most traits?
a. amphibians
b. dinosaurs and birds
c. *primates
d. ray-finned fish
e. sharks
2. Which node represents the most recent
common ancestor of amphibians and primates?
a. B
b. *C
c. D
d. E
e. F
3. In the tree below, assume that the ancestor had a long tail, ear flaps, external testes, and fixed claws. Based
on the tree and assuming that all evolutionary changes in these traits are shown, what traits do bears have?
Note: Traits shown on the tree should be matched to the nearest red line.
a. long tail, ear flaps, external testes, and fixed claws
b. short tail, no ear flaps, external testes, and fixed
claws
c. short tail, no ear flaps, abdominal testes, and fixed
claws
d. *short tail, ear flaps, external testes, and fixed claws
e. long tail, ear flaps, abdominal testes, and retractable
claws
4. Speciation has occurred when two or more subpopulations:
a. Become geographically separated from one another
b. *Achieve reproductive isolation
c. Experience genetic divergence
d. Compete for limiting resources
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NAME: ________________________________ PID: ______________ Group Name: _________________
BioSci 110, Fall 08
Exam 3
5. Hurricane Katrina had a devastating effect on New Orleansʼ historic population of Live Oaks, many of which
were well over 100 years old. Oaks in low-lying areas were particularly devastated - many died as a result of
having their roots submerged in the floodwaters for weeks. Oaks occurring on higher ground were more likely to
survive because they did not experience long-term flooding. The change in allele frequencies that occurred in
New Orleansʼ Live Oaks is an example of:
a. *Genetic drift
b. Gene flow
c. Artificial selection
d. Natural selection
e. Sexual selection
6. Carl Woeseʼs work in the 1970ʼs and 80ʼs used RNA sequences to construct phylogenetic trees for different
groups of organisms. His results indicated:
a. Relationships cannot be determined by molecular methods
b. Whittakerʼs 5-kingdom classification is an accurate representation of evolutionary relatedness
c. *Prokaryotes are more diverse than initially thought
d. Heterotrophs are not related to autotrophs
7. Cows have bacteria that live in their digestive tract that help them digest cellulose from grasses. The bacteria
allow the cows to extract more nutrients and calories from grass than they would if they didnʼt have these
bacteria. The bacteria live their entire life cycle within the gut of the cow and do not survive outside of the cow
gut. The relationship between the cow and its gut bacteria is an example of a:
a. commensalism
b. competition
c. * mutualism
d. parasitism
e. predation
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NAME: ________________________________ PID: ______________ Group Name: _________________
BioSci 110, Fall 08
Exam 3
In the 1970ʼs, evolutionary biologist, John Endler began studying wild populations of guppies in Venezuela. He
was impressed by the range of variation he observed among guppies living in different pools within the same
stream. Endler carefully measured size, color, and placement of spots on guppies and started to observe a
strong correlation between where guppies lived in a particular stream and whether male fish were bright or drab.
Female guppies are all drab, regardless of location. Data from 3 pools within the same stream are indicated in
the table below.
Pool
Number
guppies
Average Male Coloration
Average Female
Coloration
Number of Predators
1
100
Bright, multi-colored,
large spots
drab, small spots
2
100
Medium color, medium
spots
drab, small spots
3
100
Drab colors, small spots
near tail
drab, small spots
Pike cichlids: 0
Blue acara: 0
Rivulus: 12
Pike cichlids: 0
Blue acara: 7
Rivulus: 15
Pike cichlids: 17
Blue acara: 20
Rivulus: 5
Pool 2
Pool 1
Pool 3
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NAME: ________________________________ PID: ______________ Group Name: _________________
BioSci 110, Fall 08
Exam 3
____ 1. (2 pts) Describe 2 potential consequences that variation in male coloration might have on fitness in
guppies.
- bright colors could attract more females
- drab color may benefit guppies by allowing them to escape predation (camouflage)
____ 2. (1 pt) In describing the relationship between male coloration and fitness, [male coloration / fitness] is the
dependent variable. Fitness
___ 3. (5 pts) Construct a graph that shows your prediction about the relationship between male coloration and
fitness for each of the 3 pools. You may construct this as 3 separate graphs or as 3 plots within the same
graph. In either case, label axes and indicate which plot is associated with Pool 1, Pool 2, and Pool 3.
Pool 1
Fitness
Pool 2
Pool 3
Male coloration (drab  bright)
____ 4. (9 pts) For each of the 3 pools, indicate whether you think selection is or is not acting on the population,
what the likely selective agent is, and the basis for your claim.
If yes, what is
the likely
selective
agent?
Describe your rationale for determining whether selection is or is not
a factor for this population.
Pool 1
Do you think
selection is
acting on
this
population?
yes
female
choice
Pool 2
yes
Pool 3
yes
female
choice AND
predators
predators
There are more bright than dull males. Predator pressure is lowest
in this pool, so bright colors are not a significant risk. Females are
all dull – indicating the variation in the males is due to female choice
(sexual selection). Because predator pressure is low, males gain a
mating advantage if they are bright.
intermediate color is most abundant in this population due to
opposing selective pressures both acting on the guppies (sexual
selection and predation)
predators are most abundant in this pool, so bright color is risky.
Males that are camouflaged (drab) have the highest fitness.
____ 5. (3 pts) An undergraduate research assistant conducts a project in which she moves 50 guppies from
Pool 1 into Pool 3 and observes the fish over several months. Predict the outcome of her experiment and
explain your rationale.
It is likely that survival (thus, fitness) will be low for the transported guppies. Pool 1 guppies are mostly bright –
this is the least favored phenotype in Pool 3 due to the abundance of predators. Bright-colored males will be
most attractive to females, but are at a high risk for predation.
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NAME: ________________________________ PID: ______________ Group Name: _________________
BioSci 110, Fall 08
Exam 3
____ 6. (10 pts) A complete explanation of natural selection would include 5 fundamental principles of evolution
indicated in the left column of the table below. In the right column, explain (in a sentence or less) how each
concept is represented in (or relevant to) the case of guppy coloration in Venezuelan streams.
Genetic Variation
Origin of Variation
Inheritance
Fitness
Population Change
Individual guppies in the population differ from one another in coloration and spot
patterns. Genetic differences (e.g., different alleles) account for the phenotypic variation
we see in the color and spot patterns of the guppies. (+2)
+1 = phenotypic differences are observed
+1 = phenotype differences are linked to genotype differences
Random mutations in existing alleles result in different sequences of bases, thus
new alleles. Random mutations resulted in alleles for brighter coloration and spots in the
guppies. (+2)
Genetic information is passed from parent to offspring through the gametes.
New alleles that conferred brighter colors were passed on to offspring of the guppies. (+2)
+1 = genetic information is passed from parent to offspring through gametes
+1 = more “fit” alleles are passed on to offspring
Guppies differ in their ability to reproduce, and this difference is based on their
phenotypes and is influenced by the environment. (+2)
Alleles for bright colored guppies conferred the greatest fitness advantage, and therefore
guppies displaying these phenotypes will survive and reproduce, passing on their genes
to their offspring. Over time, the alleles for bright color will become more abundant in the
population (because bright colored guppies are reproducing the most) and the population
will change to become brighter, on average. (+2)
+1 = Guppies with a higher fitness reproduce more
+1 = Overtime, the frequency of alleles changes to reflect these different rates
of reproduction
____ 7. (12 pts) In a box-and-arrow model, concepts are structures that are linked by behaviors. Behaviors
are short phrases or linking words that clearly and concisely describe the relationship between structures.
Behaviors are generally active, and therefore tend to be verbs, while structures are concepts or nouns.
a. (10 pts) In the space below, construct a box and arrow model that demonstrates your understanding of the
following concepts in the context of this problem about guppy coloration: gene, allele, DNA molecule,
chromosome, protein, phenotype, mutation, genetic variation, fitness, and selection. Use language in the
structures and behaviors of your model that are specific to this case. For example, instead of using “gene” as a
structure in your model, use “gene for ___” indicating the specific type of gene relevant to the guppy case.
Each concept listed above is represented accurately in association with a correct behavior.
2 pts awarded for correctly representing the associations indicated below, with correct/accurate
descriptive words:
(1) chromosome-DNA: DNA is represented as being equivalent to or a component of a chromosome;
hierarchical organization is represented correctly
(2) gene-mutation-allele-variation: alleles are indicated as alternative versions of genes; new alleles
arise as the result of mutations in existing genes. The consequence of mutations in existing alleles is
that new alleles arise. Mutation is the origin of all variation and the ultimate source of genetic variation
in a population
(3) protein-phenotype: alternative alleles code for the production of different proteins that are expressed
as different phenotypes. Individuals in a population differ in their phenotypes owing to the activity of
proteins encoded by different alleles.
(4) variation–selection–fitness: selection acts on variation in the population; as a result, certain
phenotypes have increased or decreased fitness
(5) model was specific to the guppy problem
b. (2 pts) In a sentence or less, what is the function of your model?
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NAME: ________________________________ PID: ______________ Group Name: _________________
BioSci 110, Fall 08
Exam 3
The model should illustrate both: a) how genetic and phenotypic variation arises in a population, and b) how
environment acts on that variation resulting in differential fitness for different phenotypes (i.e., evolution by
natural selection).
Variable – must be consistent with information represented in model and must go beyond the function
of “origin of variation” because selection and fitness have been added to this model. Anticipated
functions include: evolution of the guppy population.
____ 8. (8 pts) In Endlerʼs data, 3 species of fish (pike cichlids, blue acara, and rivulus) were listed as predators
of guppies.
Pike Cichlid
Blue Acara
Rivulus
Guppy
a. (4 pts) Describe 2 adaptations that help (or could help) the predators above become more successful in
preying on guppies. Explain how the adaptations you list are adaptive.
Lots of answers: bigger and sharper teeth, faster (more hydrodynamic), bigger eyes, etc.
1 pt each for naming a trait; 1 pt for explaining HOW it is adaptive
b. (4 pts) Describe 2 adaptations that help (or could help) guppies become more successful in avoiding
predation. Explain how the adaptations you list are adaptive.
Lots of answers: faster (more hydrodynamic), dull coloration (camouflage), toxins, etc.
1 pt each for naming a trait; 1 pt for explaining HOW it is adaptive
____ 9. (8 pts) Consider the interactions between two of the predatory fish, blue acara and pike cichlids.
a. (1 pt) What type of ecological interaction characterizes the relationship between blue acara and pike cichlids?
a. commensalism
b. *competition
c. mutualism
d. parasitism
e. predation
b. (2 pts) In a sentence or less, explain your answer.
As predators, they overlap in their use of a limiting resource (they both feed on a limited number of guppies) –
that is the definition of competition.
c. (3 pts) BRIEFLY describe (or draw) a simple experiment you could perform to confirm the type of interaction
you predicted for the blue acara and rivulus. - this question was not counted in the scoring –
You could: a) supplement the limiting resource – add more guppies than either population could possibly
consume, or b) isolate the populations of acara and rivulus
d. (2 pts) Describe the results from your experiment that would confirm your prediction about the type of
interaction between blue acara and pike cichlids.
If competition were a factor between acara and rivulus (or cichlids), then fitness of each should go up following
either experiment. This would support the prediction of competition b/c when populations compete, fitness for
both is reduced through the competitive interaction.
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NAME: ________________________________ PID: ______________ Group Name: _________________
BioSci 110, Fall 08
Exam 3
____ 10. (14 pts) For questions a – f, you must show your work to receive full credit, including all equations and
calculations!
This problem was completed through a clicker series in class on 11/25.
In guppies, fan-shaped tails result from the expression of a recessive allele, f. In one of Endlerʼs pools, 64 of the
100 guppies had a fan-shaped tail.
a. (1 pt) What is the Hardy-Weinberg predicted frequency of the f allele (q) in this population of guppies?
Here, we start by assuming that the population is in HWE. If so, then the frequency of 64/100 (.64) represents
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the frequency of the homozygous, recessive genotype, ff. This is represented in HWE as q ; therefore, q = .64.
To solve for q, take the square root. q = .8
b. (1 pt) What is the Hardy-Weinberg predicted frequency of the F allele (p) in this population of guppies?
P = 1 – q = 1 - .8 = .2
c. (4 pts) Calculate the Hardy Weinberg predicted frequencies for all possible genotypes.
2
2
PREDICTED genotype frequencies are generated from the HWE equation: p + 2pq + q = 1
2
2
FF: HWE predicted value is p = (.8) = .64
Ff: HWE predicted value is 2pq = 2(.8)(.2) = .32
2
2
ff: HWE predicted value is q = (.2) = .04
d. (4 pts) Researchers observed that there were no heterozygotes in this population of guppies. Calculate the
observed genotype frequencies for this population.
FF: 1 - .64 = .36
Ff: 0
ff: 64/100 = .64
e. (2 pts) Without actually calculating Chi-Square, do you expect that this population is or is not in HardyWeinberg equilibrium? Explain.
If the values for predicted and observed genotype frequencies are similar, then the population IS in HWE.
If the values for predicted and observed genotype frequencies are different, then the population IS NOT in
HWE.
f. (2 pts) Assume that your conclusion in “e” is verified statistically. What is the biological interpretation of this
outcome? (i.e., what does this mean?)
If you said they are similar, this indicates the population is NOT evolving
If you said they are different, this indicated the population is evolving
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