OCR GCSE Biology A: Variation, natural selection, evolution and classification (J247) – 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 B5.2 Natural selection and evolution in OCR GCSE (9-1) Gateway Science Biology A (J247), Version 4.0 (August 2026), outcomes B5.2a to B5.2f. No B5.2 statement is shown in bold type, so none is Higher Tier only. Use the study guide and revision notes first. Course links: OCR GCSE Biology hub, checklist and free diagnostics.

Questions

1. State what is meant by genetic variation, and give two sources of it. [3]

2. Distinguish between natural and artificial classification, and give an example of an artificial grouping. [3]

3. A researcher released 80 pale and 120 dark ground beetles onto dark volcanic soil. One year later, 10 pale and 90 dark beetles from the release were still alive.

(a) Calculate the percentage of each colour that survived. [2] (b) Explain these results using natural selection. [3]

4. A student writes: “The lizards grew longer legs to run away from snakes, and passed longer legs on to their young.” Explain two errors in this statement, then rewrite it correctly. [4]

5. A gene of 250 bases was sequenced in three species. Species J and K differ in 5 bases, J and L differ in 30 bases, and K and L differ in 28 bases.

(a) Calculate the percentage difference for J and K, and for J and L. [2] (b) State which two species share the most recent common ancestor. [1] (c) Explain how DNA sequencing can lead to a different classification from one based on appearance. [2]

6. A culture contains 4.0 × 10⁶ bacteria. One in every 2.0 × 10⁶ carries an allele for resistance to an antibiotic. The antibiotic is added and kills every non-resistant cell. Resistant cells divide every 30 minutes.

(a) Calculate the number of resistant bacteria at the start. [1] (b) Calculate the number of resistant bacteria after 4 hours, assuming none die. [2] (c) Explain why a second dose of the same antibiotic is much less effective. [2]

7. A bacterial sample from a patient formed a clear zone of 24 mm diameter around a disc of an antibiotic. A sample taken after a long treatment course formed a zone of 12 mm diameter around the same type of disc.

(a) Calculate the percentage decrease in zone diameter. [2] (b) Explain what the change suggests about the bacteria. [2]

8. The mean limb length of an extinct mammal was measured from fossils in three rock layers: 14 cm (oldest layer), 19 cm (middle layer) and 25 cm (youngest layer).

(a) Calculate the percentage increase in mean limb length from the oldest to the youngest layer, to one decimal place. [2] (b) Describe what the data suggest about the species. [2] (c) Give two reasons why the fossil record is incomplete. [2]

9. (a) Describe the contribution of Alfred Russel Wallace to the theory of evolution by natural selection. [2] (b) Explain one way in which the theory has affected modern biology. [2]

10. A seedbank stores 2000 seeds of a rare wild plant. A test shows that 85% will germinate.

(a) Calculate how many of the stored seeds are expected to germinate. [2] (b) Explain how seedbanks help to conserve biodiversity. [2]

11. A species of mouse lives on one landmass. Rising sea levels split it into two populations on separate islands with different climates. Explain how two new species could form. [6]

12. In a hospital, 2% of samples of a bacterium were resistant to an antibiotic in year 1. In year 8, 9% were resistant.

(a) Calculate the percentage increase in the proportion of resistant samples. [2] (b) Explain how heavy use of the antibiotic could cause this increase. [4] (c) Suggest one way to slow the rise. [1]

Answers

1. Differences between individuals of a species caused by different alleles [1]. Any two sources: mutation, meiosis, random fertilisation [1][1] [3] Examiner insight: “Differences” alone is too vague. Mention alleles or genes, or an answer could describe environmental variation.

2. Natural classification uses many features and shows how organisms are related by ancestry [1]. Artificial classification uses a few chosen, convenient features [1]. Example: grouping animals by whether they can fly, or by living in water [1] [3] Examiner insight: A bare example with no statement of what the basis is does not show you know the difference, so state the basis for each type.

3. (a) Pale: 10 / 80 × 100 = 12.5% [1]. Dark: 90 / 120 × 100 = 75.0% [1] (b) Dark beetles were better camouflaged on dark soil, so fewer were eaten by predators [1]. They were more likely to survive and reproduce, passing on the allele for dark colour [1]. Over many generations the allele would become more common in the population [1] [5] Examiner insight: Percentages are worked out from the number released, not from the survivors. In the explanation, “survive” needs “and reproduce” and the allele being passed on to complete the chain.

4. Error 1: individuals do not change in order to survive or grow features because they need them [1]. Variants with different leg lengths already existed because of random mutation [1]. Error 2: it describes one generation of individuals instead of a change in a population over time [1]. Correct version: lizards with alleles for longer legs escaped snakes more often, survived and reproduced, so the allele became more common over generations [1] [4] Examiner insight: A rewrite that still says the lizards “needed” or “wanted” longer legs repeats the misconception, even if other words are corrected.

5. (a) J and K: 5 / 250 × 100 = 2.0% [1]. J and L: 30 / 250 × 100 = 12.0% [1] (b) J and K [1] (c) Organisms can look alike because similar environments select similar features, although they are not closely related [1]. DNA sequences show the number of differences, which reflects relatedness, so the groups can be changed [1] [5] Examiner insight: In (b), give the pair and, where a reason is wanted, link fewer differences to a more recent common ancestor.

6. (a) 4.0 × 10⁶ / 2.0 × 10⁶ = 2 resistant bacteria [1] (b) 4 hours = 8 divisions of 30 minutes [1]. 2 × 2⁸ = 2 × 256 = 512 [1] (c) The population now consists mostly of resistant bacteria descended from the survivors [1]. The resistance allele has been passed on, so the antibiotic no longer kills most of them [1] [5] Examiner insight: Show the number of divisions before the power of 2. A bare “512” is easier to credit when the working is visible.

7. (a) (12 - 24) / 24 × 100 = -50%, a decrease of 50% [1][1] (b) The bacteria have become less susceptible, so more are resistant [1]. Resistant bacteria survived the treatment, reproduced and passed on the allele [1] [4] Examiner insight: Percentage change is taken against the original value. Say the antibiotic selected resistant bacteria; saying it “made” them resistant loses the point.

8. (a) (25 - 14) / 14 × 100 [1] = 78.6% [1] (b) Limb length increased through the layers [1], so characteristics of the species changed over time, which supports evolution [1] (c) Any two: soft-bodied organisms decay and leave no fossil; most organisms do not die where fossils form; fossils destroyed by rock movement; many fossils not yet found [1][1] [6] Examiner insight: For “describe the data”, quote figures. For the incomplete record, two different reasons are needed, not one reason said twice.

9. (a) Wallace independently developed the idea of evolution by natural selection [1]. His work, from collecting specimens in south-east Asia, was presented together with Darwin’s in 1858 [1] (b) Any one explained: it explains how organisms are related, which underpins classification; it explains how antibiotic resistance arises; it supports conservation of variation [1] with a link, such as seedbanks storing seeds to keep genetic variation [1] [4] Examiner insight: “Explain” asks for the effect as well as the name of the impact, so give a consequence.

10. (a) 85 / 100 × 2000 [1] = 1700 seeds [1] (b) Seedbanks store seeds of many species, kept cold and dry, so that a species can be regrown if it dies out in the wild [1]. Storing seeds from many plants keeps genetic variation that may be needed if the environment changes [1] [4] Examiner insight: “To protect biodiversity” restates the question. Say what is stored and what it allows later.

11. Sea splits the mice, so the populations no longer interbreed [1]. The climates differ, so the selection pressures differ [1]. Mice with different alleles survive and reproduce on each island [1]. Different random mutations also occur in each population [1]. Over many generations the populations become increasingly different [1]. If they met, they could no longer interbreed to produce fertile offspring, so they are separate species [1] [6] Examiner insight: A six-mark explanation gains credit by following a clear sequence. The end point, no fertile offspring, is the test for separate species.

12. (a) (9 - 2) / 2 × 100 [1] = 350% [1] (b) A random mutation produced a resistance allele in some bacteria [1]. The antibiotic killed non-resistant bacteria but resistant ones survived [1]. The resistant bacteria reproduced and passed on the allele [1]. The proportion of resistant bacteria rose over generations [1] (c) Reduce antibiotic use, for example not prescribing for viral infections [1] [7] Examiner insight: A rise from 2% to 9% is 7 percentage points but 350% as a percentage increase; answer what the question asks. State that the mutation was random and already present.

Where marks are usually lost

• Writing that individuals adapt or evolve rather than that a population changes across generations.
• Saying organisms change “in order to” or “because they need to”.
• Missing “reproduce” and “pass on the allele” from natural selection answers.
• Describing artificial classification without naming its basis.
• Dividing by the new value instead of the original when finding percentage change.
• Describing a trend without quoting figures from the data.
• Giving one reason for an incomplete fossil record twice in different words.
• Saying antibiotics cause resistance, rather than selecting for resistant bacteria.
• Writing “biodiversity” in a seedbank answer without saying what is stored.

Next steps

• Review the revision notes and the study guide.
• Return to the OCR GCSE Biology hub and tick off topics on the checklist.
• Take all free 10-minute diagnostics.
• Book a free trial class.

Official syllabus

OCR, GCSE (9-1) Gateway Science Biology A (J247) specification, Version 4.0 (August 2026), first assessment 2018, topic B5.2.