Cambridge IGCSE Biology 0610: Variation and selection – Practice Questions

These are original questions written for Marlbridge, for revision and practice on this content. They are not reproduced past-paper questions, and they do not replicate the exam’s exact structure, question count or mark tariffs – examination boards hold copyright in their own papers. Use these alongside the official past papers from your board or school.

These questions cover topic 18, Variation and selection, of the Cambridge IGCSE Biology 0610 syllabus for examination in 2026, 2027 and 2028: sections 18.1 Variation, 18.2 Adaptive features and 18.3 Selection. Questions without a label use Core content and suit every candidate. Questions labelled (Extended) test Supplement content, which only Extended candidates (Papers 2 and 4) need.

Links: study guide · revision notes · course hub · checklist · Core diagnostic · Extended diagnostic · Inheritance practice

Questions

1. Define the term variation. [1]

2. State whether each of these features shows continuous or discontinuous variation.

(a) body length of adult salmon [1] (b) seed shape in peas [1] (c) ABO blood group [1] (d) mass of apples picked from one tree [1]

3. A student measured the shell length of 40 limpets on a rocky shore.

Shell length / mm	20–24	25–29	30–34	35–39	40–44
Number of limpets	4	9	15	8	4

(a) State the type of variation shown by shell length. Give a reason for your answer. [2] (b) Calculate the percentage of limpets in the modal class. [2] (c) State the type of graph the student should draw to display these data. [1] (d) Suggest one environmental factor that could affect the shell length of a limpet. [1]

4.

(a) Describe what is meant by mutation. [1] (b) State the importance of mutation in producing variation. [1] (c) State two factors that increase the rate of mutation. [2]

5. (Extended)

(a) Describe what is meant by a gene mutation. [2] (b) Mutation is one source of genetic variation in populations. State three other sources. [3]

6. A species of small fox lives in hot, sandy deserts. It has very large ears with many blood vessels close to the skin surface, thick fur on the soles of its feet, and sand-coloured fur.

(a) Describe what is meant by an adaptive feature. [2] (b) Explain how two of the features described help the fox to survive in its environment. [4]

7. (Extended) A grass that grows on sand dunes has leaves that roll up in dry weather. The stomata are on the inner surface of the rolled leaf, sunk in grooves lined with hairs. The outer surface has a thick waxy cuticle. Explain how these features reduce water loss from the leaf. [5]

8. (Extended) A water lily is a hydrophyte with large leaves that float on the surface of a pond.

(a) Explain why the stomata of the floating leaves are on the upper surface. [2] (b) Explain the advantage to the water lily of having large air spaces in its leaves and stems. [2]

9. A species of grasshopper lives in grassland. Most grasshoppers in the population are green, but a few are brown. The colour is controlled by genes. Birds feed on grasshoppers and find them by sight. After several years of drought, the grass in the area stays brown for most of the year. Describe how natural selection could lead to an increase in the proportion of brown grasshoppers. [6]

10. (Extended) A sample of bacteria from a patient contained 4 000 000 bacteria. The sample was treated with an antibiotic. 200 bacteria survived.

(a) Calculate the percentage of bacteria that survived. [2] (b) The surviving bacteria were resistant to the antibiotic. State where the allele for resistance came from and describe how it arose. [2] (c) Explain how a strain of antibiotic-resistant bacteria could develop in a population exposed to this antibiotic. [4]

11. A dairy farmer used selective breeding for four generations. The table shows the mean milk yield per cow per year.

Generation	1	2	3	4
Mean milk yield / litres	4200	4650	5100	5460

(a) Calculate the percentage increase in mean milk yield from generation 1 to generation 4. [2] (b) Outline how the farmer carried out selective breeding to increase milk yield. [3] (c) State the type of variation shown by milk yield. [1] (d) Suggest two reasons why cows in generation 4 do not all produce the same yield of milk. [2] (e) (Extended) State two differences between natural selection and artificial selection. [2]

Answers

1. Differences between individuals of the same species [1].

Examiner insight: “Differences between organisms” is too vague for the mark; the definition needs “of the same species”.

2. (a) Continuous [1]. (b) Discontinuous [1]. (c) Discontinuous [1]. (d) Continuous [1].

Examiner insight: One mark per feature, so a single wrong item costs only that mark; do not hedge with “both”, which scores nothing.

3. (a) Continuous [1]; shell length can take any value in a range between two extremes [1]. (b) Modal class 30–34 mm has 15 limpets; 15 ÷ 40 × 100 [1] = 37.5% [1]. (c) A histogram [1]. (d) Any one: amount of food (algae) available; exposure to waves; temperature [1].

Examiner insight: The reason mark in (a) is separate from the answer mark; “because it is measured” alone does not describe a range of phenotypes, so give the full reason.

4. (a) Genetic change [1]. (b) Mutation is the way in which new alleles are formed [1]. (c) Ionising radiation [1]; some chemicals [1].

Examiner insight: “Radiation” is often accepted only when qualified as ionising (or a named type such as X-rays); “sunlight” or “microwaves” do not score.

5. (a) A random change [1] in the base sequence of DNA [1]. (b) Meiosis [1]; random mating [1]; random fertilisation [1].

Examiner insight: In (a) the word “random” earns its own mark; “a change in DNA” alone scores at most one of the two.

6. (a) An inherited feature [1] that helps an organism to survive and reproduce in its environment [1]. (b) Any two features, each with the feature linked to its effect and the effect linked to survival. For example:

• Large ears with many blood vessels give a large surface area for heat loss [1], so the fox can cool down in the hot desert [1].
• Sand-coloured fur gives camouflage [1], so it is less easily seen by predators or prey [1].

Also accept: fur on the soles of the feet insulates the feet from hot sand or helps grip on loose sand, so the fox can move to hunt or escape (two marks, in place of either feature above).

Examiner insight: Each feature needs a “what it does” point and a “why that helps survival” point; naming a feature without explaining it scores zero for that feature.

7. Rolled leaves trap moist air inside the roll, next to the stomata [1]. Stomata in grooves (sunken) are also surrounded by trapped moist air [1]. Hairs reduce air movement over the stomata [1]. So the water vapour concentration gradient between the leaf and the air is smaller, and less water vapour diffuses out [1]. The thick waxy cuticle reduces evaporation from the outer leaf surface [1].

Examiner insight: “Reduces transpiration” repeated for each feature earns little; the mark for the mechanism needs the smaller concentration gradient or reduced diffusion of water vapour.

8. (a) The lower surface is in contact with water [1], so stomata on the upper surface allow gas exchange with the air (carbon dioxide in, oxygen out) [1]. (b) Air spaces make the leaves and stems buoyant, so leaves float at the surface [1] and receive more light for photosynthesis / store air for gas exchange [1].

Examiner insight: In (b) “to float” is one point; the second mark needs the consequence, such as more light for photosynthesis.

9.

• There is variation in colour, caused by different alleles [1].
• Grasshoppers produce many offspring [1].
• There is a struggle for survival; birds see green grasshoppers more easily on brown grass, so more green ones are eaten [1].
• Brown grasshoppers are better adapted / camouflaged, so more survive [1].
• Brown grasshoppers reproduce and pass on the alleles for brown colour to their offspring [1].
• Over many generations the proportion of brown grasshoppers increases [1].

Examiner insight: Six separate creditworthy points are needed for six marks; answers that say grasshoppers “turn brown to hide” score nothing for that idea because individuals do not change.

10. (a) 200 ÷ 4 000 000 × 100 [1] = 0.005% [1]. (b) From a mutation [1], which is a random change in the base sequence of DNA [1]. (c) The antibiotic kills non-resistant bacteria [1]. Resistant bacteria survive and have less competition [1]. They reproduce and pass on the resistance allele [1]. Over many generations the resistant strain becomes common [1].

Examiner insight: Statements that the antibiotic “caused” the mutation, or that bacteria “became immune”, contradict the mark scheme idea and cost the linked mark.

11. (a) (5460 − 4200) ÷ 4200 × 100 [1] = 30% [1]. (b) Select cows with the highest milk yield (and bulls from high-yielding mothers) [1]. Cross them to produce offspring [1]. Select the offspring with the highest milk yield and breed from them, repeating over many generations [1]. (c) Continuous [1]. (d) Genetic differences: cows still have different alleles [1]; environmental differences, such as diet or health [1]. (e) In natural selection the environment decides which individuals reproduce, in artificial selection humans do [1]; natural selection favours features that aid survival, artificial selection favours features useful to humans / natural selection is usually slower [1].

Examiner insight: For a percentage increase, dividing by the final value (5460) instead of the original (4200) loses the accuracy mark; show the subtraction and division so the method mark is still available.

Where marks are usually lost

• Leaving out “of the same species” when defining variation.
• Calling a measured feature discontinuous because values are rounded.
• Drawing a bar chart with gaps for continuous data.
• Writing “radiation” without “ionising”, or “mutation is caused by radiation” as a definition.
• Naming adaptive features without explaining how each helps survival or reproduction.
• For xerophytes, missing the idea of a reduced water vapour gradient.
• Describing individuals changing during their lifetime instead of allele frequencies changing over generations.
• Saying the antibiotic caused the resistance mutation.
• Selective breeding answers that stop after one generation or never select the offspring.
• Dividing by the wrong value in a percentage increase.

Next steps

• Variation and selection revision notes
• Variation and selection study guide
• Inheritance study guide
• Cambridge IGCSE Biology course hub
• 0610 printable checklist
• 0610 Core diagnostic and 0610 Extended diagnostic
• Book a free trial class

Official syllabus

Cambridge IGCSE Biology 0610 syllabus for examination in 2026, 2027 and 2028 (Version 3), Cambridge University Press & Assessment. Topic 18 Variation and selection, sections 18.1–18.3.