,Population Genetics and Essential Biology I
Practice Exam questions and correct
answers– Updated 2026 (Graded A+) instant
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Subject: Biology I with Laboratory
Subtopic: Population Genetics Fundamentals
Question 1:
A population of beetles contains 640 black individuals and 360 brown individuals. Assuming
black coloration is dominant and the population is in Hardy-Weinberg equilibrium, what is the
frequency of the recessive allele if brown coloration is recessive?
A) 0.20
B) 0.36
C) 0.40
D) 0.60
Correct Answer: D - 0.60
Rationale: Brown individuals represent the recessive phenotype (q²). The recessive frequency
equals 360/1000 = 0.36. Therefore, q = √0.36 = 0.60. Option A and C represent incorrect
calculations, while B represents q² rather than q. Hardy-Weinberg problems require
distinguishing genotype frequencies from allele frequencies.
Question 2:
A population will remain in Hardy-Weinberg equilibrium only if:
A) Natural selection strongly favors one allele
B) Mutation rates are extremely high
C) Random mating occurs and evolutionary forces are absent
D) The population size continually decreases
Correct Answer: C - Random mating occurs and evolutionary forces are absent
,Rationale: Hardy-Weinberg equilibrium requires no selection, mutation, migration, genetic drift,
and random mating in a large population. Selection, mutation, and population decline all violate
equilibrium assumptions.
Question 3:
Which evolutionary mechanism is most likely responsible for a sudden change in allele
frequency after a natural disaster drastically reduces population size?
A) Gene flow
B) Genetic drift
C) Mutation
D) Nonrandom mating
Correct Answer: B - Genetic drift
Rationale: A severe reduction in population size produces a bottleneck effect, a form of genetic
drift. Allele frequencies change due to chance rather than adaptation. Gene flow requires
migration, mutation occurs slowly, and nonrandom mating does not directly explain the rapid
change.
Question 4:
Two previously isolated populations begin interbreeding. The movement of alleles between
populations is known as:
A) Genetic drift
B) Gene flow
C) Stabilizing selection
D) Sexual selection
Correct Answer: B - Gene flow
Rationale: Gene flow occurs when individuals or gametes move between populations,
introducing new alleles. Drift involves random changes, while selection involves differential
reproductive success.
Question 5:
In a population with p = 0.7 and q = 0.3, the expected frequency of heterozygotes is:
, A) 0.09
B) 0.21
C) 0.42
D) 0.49
Correct Answer: C - 0.42
Rationale: Hardy-Weinberg predicts heterozygote frequency as 2pq. Therefore, 2(0.7)(0.3) =
0.42. The remaining values correspond to p², pq, or q² calculations.
Subtopic: Natural Selection
Question 6:
A bird population exhibits intermediate beak sizes that survive better than both small and large
beaks. This represents:
A) Directional selection
B) Stabilizing selection
C) Disruptive selection
D) Artificial selection
Correct Answer: B - Stabilizing selection
Rationale: Stabilizing selection favors intermediate phenotypes while selecting against extremes.
Directional selection favors one extreme, whereas disruptive selection favors both extremes.
Question 7:
Industrial melanism in peppered moths is a classic example of:
A) Genetic drift
B) Artificial selection
C) Directional selection
D) Gene flow
Correct Answer: C - Directional selection
Rationale: Dark-colored moths gained a selective advantage during industrial pollution, causing
allele frequencies to shift toward one extreme phenotype.
Practice Exam questions and correct
answers– Updated 2026 (Graded A+) instant
download pdf
Subject: Biology I with Laboratory
Subtopic: Population Genetics Fundamentals
Question 1:
A population of beetles contains 640 black individuals and 360 brown individuals. Assuming
black coloration is dominant and the population is in Hardy-Weinberg equilibrium, what is the
frequency of the recessive allele if brown coloration is recessive?
A) 0.20
B) 0.36
C) 0.40
D) 0.60
Correct Answer: D - 0.60
Rationale: Brown individuals represent the recessive phenotype (q²). The recessive frequency
equals 360/1000 = 0.36. Therefore, q = √0.36 = 0.60. Option A and C represent incorrect
calculations, while B represents q² rather than q. Hardy-Weinberg problems require
distinguishing genotype frequencies from allele frequencies.
Question 2:
A population will remain in Hardy-Weinberg equilibrium only if:
A) Natural selection strongly favors one allele
B) Mutation rates are extremely high
C) Random mating occurs and evolutionary forces are absent
D) The population size continually decreases
Correct Answer: C - Random mating occurs and evolutionary forces are absent
,Rationale: Hardy-Weinberg equilibrium requires no selection, mutation, migration, genetic drift,
and random mating in a large population. Selection, mutation, and population decline all violate
equilibrium assumptions.
Question 3:
Which evolutionary mechanism is most likely responsible for a sudden change in allele
frequency after a natural disaster drastically reduces population size?
A) Gene flow
B) Genetic drift
C) Mutation
D) Nonrandom mating
Correct Answer: B - Genetic drift
Rationale: A severe reduction in population size produces a bottleneck effect, a form of genetic
drift. Allele frequencies change due to chance rather than adaptation. Gene flow requires
migration, mutation occurs slowly, and nonrandom mating does not directly explain the rapid
change.
Question 4:
Two previously isolated populations begin interbreeding. The movement of alleles between
populations is known as:
A) Genetic drift
B) Gene flow
C) Stabilizing selection
D) Sexual selection
Correct Answer: B - Gene flow
Rationale: Gene flow occurs when individuals or gametes move between populations,
introducing new alleles. Drift involves random changes, while selection involves differential
reproductive success.
Question 5:
In a population with p = 0.7 and q = 0.3, the expected frequency of heterozygotes is:
, A) 0.09
B) 0.21
C) 0.42
D) 0.49
Correct Answer: C - 0.42
Rationale: Hardy-Weinberg predicts heterozygote frequency as 2pq. Therefore, 2(0.7)(0.3) =
0.42. The remaining values correspond to p², pq, or q² calculations.
Subtopic: Natural Selection
Question 6:
A bird population exhibits intermediate beak sizes that survive better than both small and large
beaks. This represents:
A) Directional selection
B) Stabilizing selection
C) Disruptive selection
D) Artificial selection
Correct Answer: B - Stabilizing selection
Rationale: Stabilizing selection favors intermediate phenotypes while selecting against extremes.
Directional selection favors one extreme, whereas disruptive selection favors both extremes.
Question 7:
Industrial melanism in peppered moths is a classic example of:
A) Genetic drift
B) Artificial selection
C) Directional selection
D) Gene flow
Correct Answer: C - Directional selection
Rationale: Dark-colored moths gained a selective advantage during industrial pollution, causing
allele frequencies to shift toward one extreme phenotype.
