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IGCSEBiology
Trial Class

Original practice · 5 questions · 14 marks · about 16 minutes

Genetic and Environmental Variation Practice Questions

Biology editorial review is supported by the named review panel. Reviewer participation may vary by guide. Checked against Cambridge IGCSE Biology 0610 (2026–2028); last reviewed August 2026.

These questions test your understanding of the causes of variation within a species and how to classify different types of variation.

Before you open the answers

  • Attempt every question without notes.
  • Show working for calculations and write complete biological statements.
  • Use the suggested time as a guide, not a strict limit on the first attempt.

These are original practice questions. They do not reproduce an official Cambridge paper or official mark scheme.

  1. Question 1

    Paper 2 Both 3 marks Difficulty 2/5

    Distinguish between continuous and discontinuous variation. Give one example of each.

    Show model answer and marking guidance
    1. Continuous: variation shows a range of values with no distinct categories: e.g. Height, mass, hand span.
    2. Discontinuous: variation falls into distinct categories with no intermediates: e.g. Blood group (A, B, AB, O), tongue rolling.
    3. Continuous variation is often controlled by multiple genes and the environment; discontinuous is usually controlled by a single gene.

  2. Question 2

    Paper 4 Extended 3 marks Difficulty 3/5

    Explain why identical twins may have different body masses despite being genetically identical.

    Show model answer and marking guidance
    1. Body mass is affected by environmental factors, not just genes.
    2. Differences in diet, exercise levels, and lifestyle.
    3. This shows that body mass is influenced by both genes and the environment.

  3. Question 3

    Paper 4 Both 3 marks Difficulty 3/5

    State three sources of genetic variation in a species.

    Show model answer and marking guidance
    1. Mutation: random changes in DNA / genes.
    2. Meiosis: crossing over and independent assortment of chromosomes produce unique gametes.
    3. Random fertilisation: any sperm can fuse with any egg, producing unique combinations.

  4. Question 4

    Paper 2 Core 2 marks Difficulty 1/5

    Define the term "variation".

    Show model answer and marking guidance
    1. Differences between individuals of the same species.
    2. Can be genetic, environmental, or a combination of both.

  5. Question 5

    Paper 4 Extended 3 marks Difficulty 4/5

    Explain why mutations are the ultimate source of all new alleles in a population.

    Show model answer and marking guidance
    1. A mutation is a change in the base sequence of DNA.
    2. This can create a new allele that codes for a different form of a protein.
    3. Without mutation, no new alleles would exist: all other sources of variation (meiosis, fertilisation) only shuffle existing alleles.

Mark the set consistently

Award a point only when the idea is clearly present in the written answer. Correct any missed point in a complete sentence, then test the same skill on a different question several days later.

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