Evolutionary Biology (PCB4674) Exam 2 2026 – FSU
1. Which of the following is the best definition of biological fitness?
A. The physical strength and speed of an individual.
B. The relative contribution of an individual to the gene pool of the next generation.
C. The ability of an individual to survive to old age.
D. The number of mates an individual acquires during its lifetime.
Answer: B
Rationale: Fitness is defined by reproductive success relative to others in the population,
measuring how many offspring are contributed to the next generation.
2. In a population undergoing directional selection, how does the mean
phenotype change over time?
A. The mean phenotype stays the same, but variance decreases.
B. The mean phenotype shifts toward the center, increasing the average.
C. The mean phenotype shifts toward one extreme of the trait distribution.
D. The population splits into two distinct phenotypic groups.
Answer: C
Rationale: Directional selection favors one extreme phenotype, causing the population
mean to shift in that direction over generations.
,3. Which mode of selection results in a reduction of phenotypic variance
without changing the mean?
A. Directional selection
B. Disruptive selection
C. Negative frequency-dependent selection
D. Stabilizing selection
Answer: D
Rationale: Stabilizing selection favors intermediate phenotypes and acts against extremes,
narrowing the distribution around the mean.
4. What is a synapomorphy?
A. A shared ancestral character state.
B. A character state unique to a single terminal taxon.
C. A trait that evolved independently in two different lineages.
D. A shared derived character state that defines a clade.
Answer: D
Rationale: Synapomorphies are derived traits shared by a group of organisms and their
most recent common ancestor, used to define monophyletic groups.
5. The presence of wings in both birds and bats is an example of:
A. Homoplasy (Convergent Evolution)
B. Synapomorphy
C. Symplesiomorphy
D. Monophyly
Answer: A
Rationale: Wings in birds and bats evolved independently to solve the same functional
problem, making them analogous structures or homoplasies.
, 6. Genetic drift has the strongest effect in:
A. Large populations with high mutation rates.
B. Small populations.
C. Populations experiencing heavy migration.
D. Populations under intense natural selection.
Answer: B
Rationale: The sampling error associated with genetic drift is inversely proportional to
population size; smaller populations experience more dramatic random fluctuations.
7. Which of the following describes a ‘founder effect’?
A. A population crash due to a natural disaster.
B. A new population started by a small number of individuals from a larger source.
C. The movement of alleles between two established populations.
D. The process where individuals with certain traits are more likely to mate.
Answer: B
Rationale: A founder effect occurs when a small group of colonists carries only a fraction
of the original population’s genetic diversity to a new location.
8. In the Hardy-Weinberg equation, what does the term ‘2pq’ represent?
A. The frequency of the dominant allele.
B. The frequency of the homozygous recessive genotype.
C. The frequency of the heterozygous genotype.
D. The total number of individuals in the population.
Answer: C
Rationale: In the equation p^2 + 2pq + q^2 = 1, p^2 is homozygous dominant, 2pq is
heterozygous, and q^2 is homozygous recessive.
1. Which of the following is the best definition of biological fitness?
A. The physical strength and speed of an individual.
B. The relative contribution of an individual to the gene pool of the next generation.
C. The ability of an individual to survive to old age.
D. The number of mates an individual acquires during its lifetime.
Answer: B
Rationale: Fitness is defined by reproductive success relative to others in the population,
measuring how many offspring are contributed to the next generation.
2. In a population undergoing directional selection, how does the mean
phenotype change over time?
A. The mean phenotype stays the same, but variance decreases.
B. The mean phenotype shifts toward the center, increasing the average.
C. The mean phenotype shifts toward one extreme of the trait distribution.
D. The population splits into two distinct phenotypic groups.
Answer: C
Rationale: Directional selection favors one extreme phenotype, causing the population
mean to shift in that direction over generations.
,3. Which mode of selection results in a reduction of phenotypic variance
without changing the mean?
A. Directional selection
B. Disruptive selection
C. Negative frequency-dependent selection
D. Stabilizing selection
Answer: D
Rationale: Stabilizing selection favors intermediate phenotypes and acts against extremes,
narrowing the distribution around the mean.
4. What is a synapomorphy?
A. A shared ancestral character state.
B. A character state unique to a single terminal taxon.
C. A trait that evolved independently in two different lineages.
D. A shared derived character state that defines a clade.
Answer: D
Rationale: Synapomorphies are derived traits shared by a group of organisms and their
most recent common ancestor, used to define monophyletic groups.
5. The presence of wings in both birds and bats is an example of:
A. Homoplasy (Convergent Evolution)
B. Synapomorphy
C. Symplesiomorphy
D. Monophyly
Answer: A
Rationale: Wings in birds and bats evolved independently to solve the same functional
problem, making them analogous structures or homoplasies.
, 6. Genetic drift has the strongest effect in:
A. Large populations with high mutation rates.
B. Small populations.
C. Populations experiencing heavy migration.
D. Populations under intense natural selection.
Answer: B
Rationale: The sampling error associated with genetic drift is inversely proportional to
population size; smaller populations experience more dramatic random fluctuations.
7. Which of the following describes a ‘founder effect’?
A. A population crash due to a natural disaster.
B. A new population started by a small number of individuals from a larger source.
C. The movement of alleles between two established populations.
D. The process where individuals with certain traits are more likely to mate.
Answer: B
Rationale: A founder effect occurs when a small group of colonists carries only a fraction
of the original population’s genetic diversity to a new location.
8. In the Hardy-Weinberg equation, what does the term ‘2pq’ represent?
A. The frequency of the dominant allele.
B. The frequency of the homozygous recessive genotype.
C. The frequency of the heterozygous genotype.
D. The total number of individuals in the population.
Answer: C
Rationale: In the equation p^2 + 2pq + q^2 = 1, p^2 is homozygous dominant, 2pq is
heterozygous, and q^2 is homozygous recessive.
