Lesson 3.4.4.1

3.4.4.1 Natural selection, adaptation and antibiotic resistance Quiz: AQA Biology, Unit 4

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 3.4.4.1, Natural selection, adaptation and antibiotic resistance: 20 multiple choice questions for the AQA Biology (7402), Unit 4: Genetic information, variation and relationships, written with Revision Ninja.

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The 20 questions

  1. What is genetic diversity within a population?

    • The number of different alleles of genes in the population.
    • The total number of individuals that are present in the population at one time.
    • The number of base pairs in the genome of a single individual in the population.
    • The number of chromosomes that are present in a single cell of the population.

  2. Why is genetic diversity important for natural selection to occur?

    • It removes all harmful alleles from the population, so no individual is ever selected against.
    • It ensures that every individual in the population has exactly the same alleles, so selection is fast.
    • It provides variation in alleles, so some individuals may be better suited to a changing environment.
    • It ensures that mutation never occurs, so the population does not change over time.

  3. Which statement describes the principle of natural selection?

    • Individuals acquire new alleles during their lifetime and pass them to all offspring in the next generation.
    • Individuals with harmful alleles always have increased reproductive success, so the allele spreads quickly.
    • Individuals with advantageous alleles have increased reproductive success, so the allele becomes more common over generations.
    • All individuals have the same reproductive success regardless of their alleles, so no selection occurs.

  4. In natural selection, what happens to a new allele that benefits its possessor in a particular environment?

    • It is inherited by members of the next generation and increases in frequency over many generations.
    • It is converted into a harmful allele by the environment, which removes it from the population.
    • It is inherited only by the individual that possesses it and is lost when that individual dies.
    • It is removed from the population in the next generation because it is always harmful.

  5. Which statement describes directional selection?

    • Selection removes all variation from the population, so every individual becomes identical over time.
    • Selection favours one extreme of a range of phenotypes, shifting the population mean in one direction.
    • Selection favours the middle of a range of phenotypes, so the extremes are removed from the population.
    • Selection favours individuals with two different alleles, so the population becomes genetically mixed.

  6. Which statement describes stabilising selection?

    • Selection favours the intermediate phenotype, so the extremes are removed from the population.
    • Selection favours one extreme phenotype, so the population mean shifts in one direction.
    • Selection has no effect on phenotypes, because stabilising selection involves only mutations.
    • Selection favours the most extreme phenotypes on both sides, so the mean is never stable.

  7. Human birth weight is an example of which type of selection, and why?

    • Directional selection, because birth weight is determined only by the number of alleles in the mother.
    • Stabilising selection, because birth weight is determined only by the environment and not by genes.
    • Stabilising selection, because very low and very high birth weights have lower survival than average weights.
    • Directional selection, because birth weight has steadily increased in every population over time.

  8. Which statement describes an adaptation that can result from natural selection?

    • A feature that appears only in individuals that have been exposed to a particular antibiotic.
    • A change in the chromosome number that happens only in individuals with no alleles at all.
    • An anatomical, physiological or behavioural feature that improves survival or reproduction in an environment.
    • A change in an individual's alleles during its lifetime in response to the environment.

  9. Which of these is an example of an anatomical adaptation?

    • The habit of an animal migrating to warmer areas during the winter months each year.
    • The ability of an animal to produce extra haemoglobin when it moves to high altitude.
    • The learned habit of a bird in using a tool to open a food container.
    • The thick fur of a polar animal, which reduces heat loss in cold conditions.

  10. Random mutation can result in new alleles of a gene. What is the main role of random mutation in natural selection?

    • It ensures that every new allele is advantageous, so selection always favours the mutant individuals.
    • It produces new alleles only in response to the environment, so mutations are always adaptive.
    • It removes existing alleles from the population so that selection can act on the remaining individuals only.
    • It creates the new alleles on which selection can act, although most mutations are harmful.

  11. A bacterial culture is grown and the number of cells is recorded over several hours. Why is a logarithmic scale useful for these data?

    • Log scales show the mass of bacteria directly, which is not possible on a linear scale.
    • Bacterial numbers are always below 10, so a log scale is needed only for very small numbers.
    • Bacterial numbers grow exponentially, so a log scale gives a clearer and more manageable representation of the data.
    • Bacterial numbers grow in a straight line, so a log scale is never needed for the data.

  12. A population of bacteria contains a resistant allele at low frequency. An antibiotic is then applied. What is the most likely result over several generations?

    • The resistant allele is converted to a susceptible allele, because the antibiotic acts directly on the DNA.
    • The frequency of the resistant allele increases, because resistant bacteria survive and reproduce more successfully.
    • The frequency of the resistant allele decreases, because the antibiotic kills all resistant bacteria first.
    • The frequency of the resistant allele is unchanged, because antibiotics do not affect bacterial alleles at all.

  13. A student claims that natural selection causes individuals to evolve during their lifetime. Evaluate this claim.

    • The claim is right, because each individual adapts to its environment by changing its alleles during its life.
    • The claim is wrong, because natural selection acts on populations over generations, not on changes within an individual's lifetime.
    • The claim is right, because natural selection only occurs when individual organisms learn new behaviours.
    • The claim is partly right, because selection acts within a lifetime only in organisms that reproduce by binary fission.

  14. A population has a large amount of genetic diversity. Which outcome is most likely if the environment changes suddenly?

    • All individuals survive equally, because diversity removes all differences in survival between individuals.
    • Some individuals are more likely to carry alleles that help them survive, so the population can adapt more easily.
    • The population becomes uniform, because genetic diversity causes every individual to have the same alleles.
    • No individuals survive, because diversity makes every individual less fit to face any environmental change.

  15. Which feature of an organism is an example of a behavioural adaptation?

    • The waxy cuticle on the leaves of a desert plant, which reduces water loss through the epidermis.
    • The hump of a camel, which stores fat that can be used as a source of energy and water.
    • Nocturnal feeding in an animal that lives in a hot desert, reducing water loss during the day.
    • The enlarged kidneys of a desert mammal, which concentrate urine and conserve water.

  16. Which two types of adaptation are described alongside anatomical adaptations in the specification?

    • Physiological and behavioural adaptations.
    • Digestive and circulatory adaptations.
    • Reproductive and developmental adaptations.
    • Genetic and chemical adaptations.

  17. A population of insects shows body lengths with the smallest and largest individuals most often killed by predators. Which type of selection is operating?

    • Directional selection, because the largest body length is always favoured by predators.
    • No selection, because predators do not cause differences in survival between insects.
    • Directional selection, because the smallest body length is always favoured by predators.
    • Stabilising selection, because the intermediate body length is favoured.

  18. A new allele reduces disease in a species only in one environment and has no effect in another. What is the most likely outcome?

    • It increases equally in all environments, because advantage does not depend on the environment.
    • It is removed in all environments immediately, because new alleles are always harmful to the population.
    • It increases in frequency in the environment where it is advantageous, but not in the other.
    • It is converted into the old allele in every environment, because alleles cannot change over time.

  19. A student claims that all adaptations are physical structures. Evaluate this claim.

    • The claim is right, because only anatomical features can be passed on to offspring.
    • The claim is right, because behaviour cannot be an adaptation, only a learned response.
    • The claim is wrong, because adaptations can also be physiological or behavioural.
    • The claim is partly right, because physiological adaptations are never inherited by the next generation.

  20. A bird population has beak lengths of 10 to 20 mm. A drought removes most of the small seeds, so birds with large beaks survive better. What change over generations is expected?

    • The mean beak length shifts towards smaller values, because small beaks are always favoured by selection.
    • The mean beak length stays the same, because the drought affects only seeds and not the birds.
    • Beak length becomes more variable, because selection always increases variation in a population.
    • The mean beak length shifts towards larger values, through directional selection.

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