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Bio 120: Principles of Evolution
Exam 1
Page 1
NAME _____________________________
1. (10 points ) Only one diagram (reproduced below) appears in The Origin of Species. Briefly explain the process
Darwin uses this figure to explain.
Bio 120: Principles of Evolution
Exam 1
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NAME _____________________________
2. (10 points) Briefly explain the Hardy-Weinberg law and its implications for evolutionary change.
3. (20 points) Mountain populations of the frog Rana clamitans are larger in body size than Piedmont populations
in North Carolina. Describe an experiment or set of experiments you would perform to determine whether this
difference in size reflects an evolved difference. Describe the possible outcomes of the experiment and what
conclusions you would draw from each possible outcome.
Bio 120: Principles of Evolution
Exam 1
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NAME _____________________________
4. (10 points) The long-term study by Woolfenden on Florida Scrub Jays showed that a helper at the nest doubled
the fitness of the mated pair being helped. In essence, this means that, relative to a fitness of 1 for an unhelped pair,
the fitness of a helped individual was 2. Woolfenden also found that virtually all individuals assisted by helpers
were either parents (degree of relatedness of "# ) or sibs (degree of relatedness of "# ). Using this information, answer
the following questions:
a. What is the magnitude of the benefit of altruism, b?
b. Assuming helping has evolved through kin selection, what is the maximum magnitude of the cost of
altruism, c?
5. (10 points) In a long-term study of the gene frequencies at the Sickle-cell locus in a Kenyan village, the frequency
of the S allele was found to be 0.1 in 1954 and 0.09 in 1980, approximately one generation later. The population of
the village between these two periods was roughly constant at 100 individuals, 30 of whom were adults. Is the
observed change in gene frequency most likely due to genetic drift or a combination of drift and natural selection?
Explain your answer.
Bio 120: Principles of Evolution
Exam 1
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6. (10 points) The picture-wing group of Drosophila on the Hawaiian islands is believed to have diversified via
repeated allopatric lineage splitting. Briefly explain how this splitting is believed to have occurred and describe two
distribution patterns exhibited by this group that is consistent with this belief.
7. (10 points) It is often said that evolutionary change can not be predicted. Briefly describe two experiments
discussed in class that disprove this statement.
Bio 120: Principles of Evolution
Exam 1
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NAME _____________________________
8. (20 points) Ipomoea purpurea is an annual plant species that grows throughout the southeastern United States.
In most populations it is polymorphic for flower color at the 'A' locus. At this locus there are two alleles, A and a.
AA individuals have darkly pigmented flowers, Aa individuals have lightly pigmented flowers, and aa individuals
have unpigmented, white flowers.
In a recent study, equal numbers of experimental seeds of each genotype were planted in the natural habitat and
were allowed to grow and reproduce. The proportions of individuals surviving to reproduce were: for AA, l œ 0.6;
for Aa, l œ 0.9; for aa, l œ 0.6. The total number of seeds produced by all surviving individuals of a given
genotype were: by AA, 12,000; by Aa, 18,000; by aa, 6,000.
Based on this information, answer the following questions:
a. What are the relative fitnesses of the three genotypes?
b. What are the gene and genotype frequencies expected to be in the next generation?
c. After the next generation, is further evolutionary change expected to occur? If so, in what
direction?
d. After 1000 generations, what is the gene frequency expected to be?
e. What assumptions did you need to make to answer questions a.  d.?
Bio 120: Principles of Evolution
Exam 1
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NAME _____________________________