CLEP Biology Mechanisms of Natural Selection 2 — Questions and Answers
Question 1: Which condition is NOT required for Hardy-Weinberg equilibrium to apply to a population?
- Random mating
- No natural selection
- Small population size (Correct answer)
- No gene flow
Correct answer: Small population size
Hardy-Weinberg equilibrium requires a large (ideally infinite) population, so small population size violates the assumptions.
Question 2: A cheetah population that went through a severe bottleneck event would most likely show:
- High genetic diversity
- Reduced genetic variation (Correct answer)
- Increased mutation rate
- Greater phenotypic variation
Correct answer: Reduced genetic variation
Bottleneck events drastically reduce population size, causing loss of alleles and reduced genetic variation.
Question 3: Disruptive selection in a population tends to:
- Favor intermediate phenotypes
- Favor both extreme phenotypes (Correct answer)
- Reduce phenotypic variation
- Favor only the largest individuals
Correct answer: Favor both extreme phenotypes
Disruptive selection favors both extreme phenotypes while selecting against intermediate ones, potentially splitting a population.
Question 4: Industrial melanism in peppered moths is a classic example of which evolutionary mechanism?
- Genetic drift
- Founder effect
- Directional selection (Correct answer)
- Balancing selection
Correct answer: Directional selection
The shift from light to dark moths during industrialization illustrates directional selection favoring the darker phenotype in polluted environments.
Question 5: Which statement best describes stabilizing selection?
- It increases variation in a population over time
- It favors extreme phenotypes at both ends
- It reduces variation by favoring intermediate phenotypes (Correct answer)
- It only operates in sexually reproducing species
Correct answer: It reduces variation by favoring intermediate phenotypes
Stabilizing selection favors the average phenotype and eliminates extremes, reducing overall variation in the population.
Question 6: Gene flow between two previously isolated populations would most likely:
- Increase genetic differences between them
- Decrease genetic differences between them (Correct answer)
- Cause speciation
- Have no effect on allele frequencies
Correct answer: Decrease genetic differences between them
Gene flow introduces alleles from one population into another, making the populations more genetically similar over time.
Question 7: Which best explains why recessive deleterious alleles persist in a population rather than being eliminated?
- They are beneficial in heterozygous form
- Natural selection cannot act on hidden recessive alleles in heterozygotes (Correct answer)
- Mutations continuously recreate them at high rates
- They are always co-dominant with the dominant allele
Correct answer: Natural selection cannot act on hidden recessive alleles in heterozygotes
When a deleterious allele is recessive, natural selection cannot eliminate it while it is 'hidden' in heterozygous carriers.
CLEP Biology Mechanisms of Natural Selection 2
Which condition is NOT required for Hardy-Weinberg equilibrium to apply to a population?