BIO 311D Organismal Biology, Ecology, and
Evolution Final Exam Study Set, 2026/2027 –
75-Question Integrative Biology Examination
with Verified Solutions
Section A: Evolution & Population Genetics (Q1–20)
1. In a population of lizards, a mutation arises that improves running speed.
Over many generations, the frequency of this allele increases. This is an
example of:
A) Genetic drift
B) Natural selection
C) Gene flow
D) Mutation pressure
Answer: B
Rationale: Natural selection increases the frequency of alleles that confer
higher fitness (survival/reproduction). Genetic drift is random, gene flow is
movement of alleles between populations, and mutation alone is weak at
changing frequencies.
2. Which of the following is required for evolution by natural selection to
occur?
A) Acquired traits are passed to offspring
B) Variation in a trait that is heritable and affects survival/reproduction
C) All individuals are genetically identical
D) The population is very small
Answer: B
Rationale: Darwin’s postulates: variation, heritability, differential
survival/reproduction, and a link between trait and fitness. Without heritable
variation that affects fitness, selection cannot act.
3. Two populations of squirrels are separated by a river and can no longer
interbreed. This is an example of:
A) Sympatric speciation
B) Allopatric speciation
,C) Peripatric speciation
D) Parapatric speciation
Answer: B
Rationale: Allopatric speciation occurs when populations are geographically
separated (e.g., by a river, mountain range). Gene flow is interrupted,
allowing divergence.
4. The biological species concept defines a species as:
A) A group of organisms that look similar
B) A group of populations that can interbreed and produce fertile offspring
C) A group that shares a common ancestor
D) A group with similar ecological roles
Answer: B
Rationale: Ernst Mayr’s biological species concept emphasizes reproductive
isolation. Morphological and phylogenetic concepts define species differently.
5. Which of the following is a prezygotic isolating mechanism?
A) Hybrid inviability
B) Hybrid sterility
C) Habitat isolation
D) Reduced hybrid fitness
Answer: C
Rationale: Prezygotic barriers prevent mating or fertilization (habitat
isolation, temporal isolation, behavioral isolation). Postzygotic barriers (A, B,
D) act after zygote formation.
6. The evolution of similar body forms in sharks (fish) and dolphins
(mammals) is an example of:
A) Convergent evolution
B) Divergent evolution
C) Coevolution
D) Sexual selection
Answer: A
Rationale: Analogous structures arise from convergent evolution when
unrelated species adapt to similar environments. Divergent evolution creates
homologous structures.
7. In the Hardy-Weinberg equation p2 +2 pq+ q2=1, what does 2 pq represent?
A) Frequency of homozygous dominant genotype
B) Frequency of homozygous recessive genotype
, C) Frequency of heterozygous genotype
D) Frequency of the recessive allele
Answer: C
Rationale: p2 = AA, 2 pq = Aa, q 2 = aa. Allele frequencies: p (dominant), q
(recessive).
8. A population of birds has genotype frequencies: AA = 0.36, Aa = 0.48, aa
= 0.16. Is this population in Hardy-Weinberg equilibrium?
A) Yes
B) No, because heterozygotes are too rare
C) No, because homozygotes are too common
D) Cannot determine
Answer: A
Rationale: p= √ 0.36=0.6 , q=√ 0.16=0.4 . Expected Aa = 2 pq=0.48 , which
matches observed. Population is in equilibrium.
9. The bottleneck effect is a type of:
A) Natural selection
B) Genetic drift
C) Gene flow
D) Mutation
Answer: B
Rationale: A bottleneck (sharp reduction in population size) causes random
loss of genetic variation, a form of genetic drift. It is not directional like
selection.
10. In a flowering plant, individuals with red flowers attract more pollinators
and produce more seeds than white-flowered individuals. Over time, red
flowers become more common. This is:
A) Directional selection
B) Stabilizing selection
C) Disruptive selection
D) Sexual selection
Answer: A
Rationale: Directional selection shifts the population mean toward one
extreme phenotype (red flowers). Stabilizing favors intermediate, disruptive
favors both extremes.
11. A scientist compares DNA sequences of a gene from humans,
chimpanzees, and gorillas. The human and chimpanzee sequences differ by
Evolution Final Exam Study Set, 2026/2027 –
75-Question Integrative Biology Examination
with Verified Solutions
Section A: Evolution & Population Genetics (Q1–20)
1. In a population of lizards, a mutation arises that improves running speed.
Over many generations, the frequency of this allele increases. This is an
example of:
A) Genetic drift
B) Natural selection
C) Gene flow
D) Mutation pressure
Answer: B
Rationale: Natural selection increases the frequency of alleles that confer
higher fitness (survival/reproduction). Genetic drift is random, gene flow is
movement of alleles between populations, and mutation alone is weak at
changing frequencies.
2. Which of the following is required for evolution by natural selection to
occur?
A) Acquired traits are passed to offspring
B) Variation in a trait that is heritable and affects survival/reproduction
C) All individuals are genetically identical
D) The population is very small
Answer: B
Rationale: Darwin’s postulates: variation, heritability, differential
survival/reproduction, and a link between trait and fitness. Without heritable
variation that affects fitness, selection cannot act.
3. Two populations of squirrels are separated by a river and can no longer
interbreed. This is an example of:
A) Sympatric speciation
B) Allopatric speciation
,C) Peripatric speciation
D) Parapatric speciation
Answer: B
Rationale: Allopatric speciation occurs when populations are geographically
separated (e.g., by a river, mountain range). Gene flow is interrupted,
allowing divergence.
4. The biological species concept defines a species as:
A) A group of organisms that look similar
B) A group of populations that can interbreed and produce fertile offspring
C) A group that shares a common ancestor
D) A group with similar ecological roles
Answer: B
Rationale: Ernst Mayr’s biological species concept emphasizes reproductive
isolation. Morphological and phylogenetic concepts define species differently.
5. Which of the following is a prezygotic isolating mechanism?
A) Hybrid inviability
B) Hybrid sterility
C) Habitat isolation
D) Reduced hybrid fitness
Answer: C
Rationale: Prezygotic barriers prevent mating or fertilization (habitat
isolation, temporal isolation, behavioral isolation). Postzygotic barriers (A, B,
D) act after zygote formation.
6. The evolution of similar body forms in sharks (fish) and dolphins
(mammals) is an example of:
A) Convergent evolution
B) Divergent evolution
C) Coevolution
D) Sexual selection
Answer: A
Rationale: Analogous structures arise from convergent evolution when
unrelated species adapt to similar environments. Divergent evolution creates
homologous structures.
7. In the Hardy-Weinberg equation p2 +2 pq+ q2=1, what does 2 pq represent?
A) Frequency of homozygous dominant genotype
B) Frequency of homozygous recessive genotype
, C) Frequency of heterozygous genotype
D) Frequency of the recessive allele
Answer: C
Rationale: p2 = AA, 2 pq = Aa, q 2 = aa. Allele frequencies: p (dominant), q
(recessive).
8. A population of birds has genotype frequencies: AA = 0.36, Aa = 0.48, aa
= 0.16. Is this population in Hardy-Weinberg equilibrium?
A) Yes
B) No, because heterozygotes are too rare
C) No, because homozygotes are too common
D) Cannot determine
Answer: A
Rationale: p= √ 0.36=0.6 , q=√ 0.16=0.4 . Expected Aa = 2 pq=0.48 , which
matches observed. Population is in equilibrium.
9. The bottleneck effect is a type of:
A) Natural selection
B) Genetic drift
C) Gene flow
D) Mutation
Answer: B
Rationale: A bottleneck (sharp reduction in population size) causes random
loss of genetic variation, a form of genetic drift. It is not directional like
selection.
10. In a flowering plant, individuals with red flowers attract more pollinators
and produce more seeds than white-flowered individuals. Over time, red
flowers become more common. This is:
A) Directional selection
B) Stabilizing selection
C) Disruptive selection
D) Sexual selection
Answer: A
Rationale: Directional selection shifts the population mean toward one
extreme phenotype (red flowers). Stabilizing favors intermediate, disruptive
favors both extremes.
11. A scientist compares DNA sequences of a gene from humans,
chimpanzees, and gorillas. The human and chimpanzee sequences differ by
