Lesson 6.1.2b

6.1.2b Evolution and the Hardy-Weinberg principle Quiz: OCR Biology, Unit 7

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 6.1.2b, Evolution and the Hardy-Weinberg principle: 20 multiple choice questions for the OCR Biology (H020), Unit 7: Genetics and evolution, written with Revision Ninja.

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The 20 questions

  1. Which equation expresses the Hardy-Weinberg principle for allele frequencies?

    • p^2 + q^2 = 2
    • 2p + 2q = 1
    • p x q = 1
    • p + q = 1

  2. Under Hardy-Weinberg, which term gives the frequency of heterozygotes?

    • p^2
    • 2pq
    • q^2
    • p + q

  3. Which condition is required for allele frequencies to remain constant under the Hardy-Weinberg principle?

    • Random mating
    • High mutation rate
    • Small population size
    • Selective predation

  4. Which type of phenotype is favoured during directional selection?

    • Both extreme phenotypes
    • One extreme phenotype
    • Modal phenotypes
    • Intermediate phenotypes

  5. Which type of phenotype is favoured during stabilising selection?

    • Intermediate phenotypes
    • One extreme phenotype
    • Both extreme phenotypes
    • Rare phenotypes

  6. What process describes random changes in allele frequencies within a small population?

    • Natural selection
    • Genetic drift
    • Founder effect
    • Gene flow

  7. What occurs when a small group colonises a new area, establishing a new population?

    • Directional selection
    • Sympatric speciation
    • Bottleneck effect
    • Founder effect

  8. In a population, the frequency of allele A is p = 0.6 and of allele a is q = 0.4. What is the expected frequency of heterozygotes?

    • 0.16
    • 0.36
    • 0.48
    • 0.24

  9. In a population, the frequency of the homozygous recessive genotype (aa) is 0.04. What are p and q?

    • p = 0.4 and q = 0.6
    • p = 0.2 and q = 0.8
    • p = 0.8 and q = 0.2
    • p = 0.04 and q = 0.96

  10. The recessive phenotype occurs in 9% of a population. What is the expected frequency of carriers (heterozygotes)?

    • 0.21
    • 0.42
    • 0.49
    • 0.09

  11. A population has 36 AA, 48 Aa and 16 aa individuals. What is the frequency of allele A?

    • 0.48
    • 0.6
    • 0.36
    • 0.5

  12. In a population where p = 0.7, what is the expected frequency of the homozygous recessive genotype?

    • 0.21
    • 0.49
    • 0.30
    • 0.09

  13. What happens to genetic variation in a population following a severe bottleneck event?

    • Increased variation
    • Constant mutation rate
    • Reduced variation
    • Unchanged variation

  14. Why does genetic drift have a greater effect in small populations?

    • Higher mutation rate
    • Faster reproduction rate
    • Stronger natural selection
    • Greater chance influence

  15. What happens to the variance of a trait during stabilising selection?

    • It stays unchanged
    • It increases
    • It fluctuates wildly
    • It decreases

  16. A population of 1000 has 90 individuals with the recessive phenotype. How many heterozygotes are expected under Hardy-Weinberg?

    • 90
    • 490
    • 210
    • 420

  17. Why does strong natural selection violate the Hardy-Weinberg principle?

    • Population size increases
    • Allele frequencies change
    • Mutations stop occurring
    • Mating becomes random

  18. The recessive phenotype frequency in a population is 0.16. What is the expected frequency of the homozygous dominant genotype?

    • 0.48
    • 0.36
    • 0.16
    • 0.84

  19. How does a founder effect differ fundamentally from a population bottleneck?

    • Forms new population
    • Increases genetic diversity
    • Involves mass extinction
    • Requires geographical barriers

  20. Besides natural selection, what is essential for speciation to occur?

    • Genetic drift
    • Artificial selection
    • Reproductive isolation
    • High mutation rate

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