Evolutionary Biology (PCB4674) Exam 2 Comprehensive Quiz 2026 –
FSU
1. Which of the following is the primary reason why genetic drift has a greater
impact on small populations compared to large ones?
A. Allele frequencies are more likely to change by chance in small samples.
B. Smaller populations have higher mutation rates.
C. Small populations are always subject to stronger natural selection.
D. Small populations have more gene flow.
Answer: A
Rationale: Genetic drift is the change in allele frequencies due to random sampling. In
small populations, random fluctuations have a proportionately larger effect on the gene
pool than in large populations.
2. In the context of the Neutral Theory of Molecular Evolution, most
evolutionary changes at the molecular level are caused by:
A. Natural selection favoring beneficial mutations.
B. High rates of horizontal gene transfer.
C. Genetic drift acting on neutral mutations.
D. Environmental changes causing specific mutations.
Answer: C
Rationale: Neutral Theory suggests that most molecular variation and evolution are the
result of random genetic drift acting on mutations that do not affect fitness.
,3. What does a dN/dS ratio of greater than 1 (dN/dS > 1) typically indicate about
a protein-coding gene?
A. The gene is under purifying selection.
B. The gene is evolving neutrally.
C. The gene is a pseudogene.
D. The gene is under positive (diversifying) selection.
Answer: D
Rationale: A ratio greater than 1 means non-synonymous substitutions (which change the
amino acid) are occurring faster than synonymous ones, indicating selection for change.
4. Which species concept defines a species as a group of actually or potentially
interbreeding natural populations that are reproductively isolated from other
such groups?
A. Biological Species Concept
B. Phylogenetic Species Concept
C. Morphological Species Concept
D. Ecological Species Concept
Answer: A
Rationale: The Biological Species Concept, proposed by Ernst Mayr, emphasizes
reproductive isolation as the key factor in defining species.
5. A ‘synapomorphy’ is defined as:
A. A shared derived character state.
B. A character state unique to a single taxon.
C. A shared primitive character state.
D. An analogous structure resulting from convergent evolution.
Answer: A
Rationale: Synapomorphies are shared derived traits used in cladistics to define
monophyletic groups (clades).
, 6. What is the term for the movement of alleles from one population to
another?
A. Genetic drift
B. Mutation
C. Gene flow
D. Selection
Answer: C
Rationale: Gene flow is the transfer of genetic material between populations, often
through migration of individuals or gametes.
7. Which type of selection occurs when individuals at both extremes of a
phenotypic range have higher fitness than individuals with intermediate
phenotypes?
A. Directional selection
B. Stabilizing selection
C. Disruptive selection
D. Negative selection
Answer: C
Rationale: Disruptive (or diversifying) selection favors both extremes and can lead to
bimodal trait distribution.
8. The ‘Founder Effect’ is a specific type of:
A. Genetic drift
B. Natural selection
C. Gene flow
D. Assortative mating
Answer: A
Rationale: The Founder Effect occurs when a small group breaks off from a larger
population to establish a new one, leading to random changes in allele frequencies.
FSU
1. Which of the following is the primary reason why genetic drift has a greater
impact on small populations compared to large ones?
A. Allele frequencies are more likely to change by chance in small samples.
B. Smaller populations have higher mutation rates.
C. Small populations are always subject to stronger natural selection.
D. Small populations have more gene flow.
Answer: A
Rationale: Genetic drift is the change in allele frequencies due to random sampling. In
small populations, random fluctuations have a proportionately larger effect on the gene
pool than in large populations.
2. In the context of the Neutral Theory of Molecular Evolution, most
evolutionary changes at the molecular level are caused by:
A. Natural selection favoring beneficial mutations.
B. High rates of horizontal gene transfer.
C. Genetic drift acting on neutral mutations.
D. Environmental changes causing specific mutations.
Answer: C
Rationale: Neutral Theory suggests that most molecular variation and evolution are the
result of random genetic drift acting on mutations that do not affect fitness.
,3. What does a dN/dS ratio of greater than 1 (dN/dS > 1) typically indicate about
a protein-coding gene?
A. The gene is under purifying selection.
B. The gene is evolving neutrally.
C. The gene is a pseudogene.
D. The gene is under positive (diversifying) selection.
Answer: D
Rationale: A ratio greater than 1 means non-synonymous substitutions (which change the
amino acid) are occurring faster than synonymous ones, indicating selection for change.
4. Which species concept defines a species as a group of actually or potentially
interbreeding natural populations that are reproductively isolated from other
such groups?
A. Biological Species Concept
B. Phylogenetic Species Concept
C. Morphological Species Concept
D. Ecological Species Concept
Answer: A
Rationale: The Biological Species Concept, proposed by Ernst Mayr, emphasizes
reproductive isolation as the key factor in defining species.
5. A ‘synapomorphy’ is defined as:
A. A shared derived character state.
B. A character state unique to a single taxon.
C. A shared primitive character state.
D. An analogous structure resulting from convergent evolution.
Answer: A
Rationale: Synapomorphies are shared derived traits used in cladistics to define
monophyletic groups (clades).
, 6. What is the term for the movement of alleles from one population to
another?
A. Genetic drift
B. Mutation
C. Gene flow
D. Selection
Answer: C
Rationale: Gene flow is the transfer of genetic material between populations, often
through migration of individuals or gametes.
7. Which type of selection occurs when individuals at both extremes of a
phenotypic range have higher fitness than individuals with intermediate
phenotypes?
A. Directional selection
B. Stabilizing selection
C. Disruptive selection
D. Negative selection
Answer: C
Rationale: Disruptive (or diversifying) selection favors both extremes and can lead to
bimodal trait distribution.
8. The ‘Founder Effect’ is a specific type of:
A. Genetic drift
B. Natural selection
C. Gene flow
D. Assortative mating
Answer: A
Rationale: The Founder Effect occurs when a small group breaks off from a larger
population to establish a new one, leading to random changes in allele frequencies.
