AQA A Level Biology (7402) · Paper 2 and Paper 3
AQA A Level Biology 3.7 Genetics, Populations and Ecosystems Exam Questions
Free AQA A Level Biology exam questions by topic for 3.7 Genetics, populations, evolution and ecosystems, with a mark scheme for every pack. Covers inheritance, the chi-squared test, Hardy-Weinberg, speciation, and populations and succession.
3.7 Genetics, Populations and Ecosystems exam questions by subtopic
4 question packs covering every part of the specification, with thousands of real past exam questions between them. Do not stop after a few: answer as many as you can, without notes, and mark each one with the mark scheme. The more questions you do, the more quickly you will spot how examiners ask about each idea.
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About AQA A Level Biology topic 3.7
Topic 3.7 brings together inheritance, how allele frequencies change in populations, how new species form, and how populations interact in ecosystems. Calculations are common here: genetic crosses, the chi-squared test, Hardy-Weinberg and mark-release-recapture.
What you need to know for 3.7 Genetics, Populations and Ecosystems
- 3.7.1 Monohybrid and dihybrid crosses, codominance, multiple alleles, sex linkage, autosomal linkage, epistasis, and using the chi-squared test.
- 3.7.2 Populations, gene pools and allele frequencies, and the Hardy-Weinberg principle: p + q = 1 and p2 + 2pq + q2 = 1.
- 3.7.3 Variation, natural selection, genetic drift, stabilising, directional and disruptive selection, and allopatric and sympatric speciation.
- 3.7.4 Carrying capacity, competition and predation, estimating population size with quadrats and mark-release-recapture, succession, and conservation.
Common mistakes in 3.7 Genetics, Populations and Ecosystems
- Using q2 as q in Hardy-Weinberg. Find q2 from the recessive phenotype, then take the square root.
- Using the wrong degrees of freedom in chi-squared. It is the number of categories minus one; then say whether the difference is significant at p = 0.05.
- Mixing up autosomal linkage (genes on the same autosome) with sex linkage (genes on the X chromosome).
- Describing succession without saying how each stage changes the abiotic conditions, making them less hostile for other species.
- For speciation, not linking reproductive isolation to different allele frequencies in the separated populations.
Try three 3.7 Genetics, Populations and Ecosystems exam-style questions
1. In a population, 9% of individuals show a recessive phenotype. Calculate the percentage of heterozygotes. (2 marks)
Show the mark scheme answer
q2 = 0.09, so q = 0.3 and p = 0.7; 2pq = 2 x 0.7 x 0.3 = 0.42, so 42%.
2. 40 snails were marked and released. A second sample of 50 contained 8 marked snails. Estimate the population size. (1 mark)
Show the mark scheme answer
40 x 50 / 8 = 250.
3. Explain how allopatric speciation can occur. (3 marks)
Show the mark scheme answer
Populations are geographically isolated; different selection pressures and mutations change allele frequencies in each population; eventually they can no longer interbreed to produce fertile offspring.
Want more? Every pack above has many more past exam questions on genetics, populations and ecosystems.
3.7 Genetics, Populations and Ecosystems FAQs
What does AQA A Level Biology topic 3.7 cover?
Topic 3.7, Genetics, populations, evolution and ecosystems, covers inheritance, the chi-squared test, Hardy-Weinberg, speciation, and populations and succession.
Which AQA A Level Biology paper is topic 3.7 on?
Topic 3.7 is examined in Paper 2, which covers topics 3.5 to 3.8. Paper 3 can also include questions on any topic, so it is worth revising for that paper too.
Are these AQA A Level Biology 3.7 exam questions free?
Yes. Every question pack and mark scheme on this page is a free PDF download, with no sign-up needed.
