Genetics, Populations, Evolution and Ecosystems | AQA A-Level Biology (7402)

Genetics, Populations, Evolution and Ecosystems

125 questions
11 subtopics
Paper 2, and available on Paper 3
Paper 2 and Paper 3

Genetics, Populations, Evolution and Ecosystems is examined on Papers 2 and 3 of AQA Biology, which draw on topics 5 to 8.

118 recall questions across 11 subtopics.

Sample questions from Genetics, Populations, Evolution and Ecosystems

Answer each one closed book first, then open the answer.

Genotype, phenotype and types of allele

What is a dominant allele?

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An allele that is expressed in the phenotype when present in either homozygous or heterozygous form.
Monohybrid and dihybrid crosses, sex linkage and autosomal linkage

In a dihybrid cross between two individuals heterozygous for both genes, what phenotypic ratio is expected assuming complete dominance and independent assortment?

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9:3:3:1
Epistasis, genetic diagrams and the chi-squared test

What tool is used in a genetic diagram to show all possible combinations of gametes?

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A Punnett square.
Gene pools, allele frequency and Hardy–Weinberg

What condition regarding natural selection must be met for Hardy–Weinberg equilibrium?

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There must be no natural selection favouring or disfavouring any genotype.
Sources of variation and selection pressures

How does crossing over during meiosis contribute to genetic variation?

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Crossing over exchanges segments of DNA between homologous chromosomes during prophase I, creating new combinations of alleles on the same chromosome.
Types of selection and allopatric and sympatric speciation

What is directional selection?

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Directional selection favours one extreme phenotype, shifting the mean phenotype of the population in one direction.
Genetic drift, founder effects and the route to speciation

How does natural selection contribute to speciation?

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Natural selection causes differential survival and reproduction, leading to changes in allele frequencies that can result in populations becoming genetically distinct.
Communities, ecosystems, niches and carrying capacity

Give one example of a very small ecosystem and one example of a very large ecosystem.

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Very small: a rock pool. Very large: an ocean.

The 11 subtopics

One subtopic is one session. Work down the list.

Subtopic	What it covers	Questions
Genotype, phenotype and types of allele	Recall questions on genotype and phenotype, multiple alleles, dominant, recessive and codominant alleles, homozygous and heterozygous, and the locus of a gene.	9
Monohybrid and dihybrid crosses, sex linkage and autosomal linkage	Recall questions on monohybrid and dihybrid crosses and their expected ratios, why X-linked recessive conditions are commoner in males, autosomal linkage, and multiple alleles.	9
Epistasis, genetic diagrams and the chi-squared test	Recall questions on epistasis and its ratios, setting out a genetic diagram with gametes and a Punnett square, using the chi-squared test on crosses, and the probability of inheriting alleles.	16
Gene pools, allele frequency and Hardy–Weinberg	Recall questions on populations, gene pools and allele frequency, the conditions for the Hardy–Weinberg principle, and using its equations to find allele, genotype and carrier frequencies.	19
Sources of variation and selection pressures	Recall questions on how mutation, independent assortment, crossing over and random fertilisation cause genetic variation, and how predation, disease and competition act as selection pressures.	9
Types of selection and allopatric and sympatric speciation	Recall questions on how differential reproductive success changes allele frequencies, stabilising, directional and disruptive selection, reproductive isolation, and allopatric and sympatric speciation.	11
Genetic drift, founder effects and the route to speciation	Recall questions on genetic drift and why it matters in small populations, the founder and bottleneck effects, and how natural selection and reproductive isolation together lead to new species.	10
Communities, ecosystems, niches and carrying capacity	Recall questions on communities and ecosystems of different sizes, the niche and the abiotic and biotic factors that govern it, carrying capacity, and abiotic factors that affect population size.	8
Competition, predation, quadrats and mark-release-recapture	Recall questions on interspecific and intraspecific competition and predation, estimating population size with quadrats and belt transects, and the Lincoln index for mark-release-recapture.	9
Mark-release-recapture assumptions and succession	Recall questions on the assumptions behind mark-release-recapture estimates, ecosystems as dynamic, and primary succession from pioneer species to a climax community.	8
Succession, conservation and evaluating the evidence	Recall questions on how succession changes the environment and biodiversity, managing succession to conserve habitats, measuring abundance, and judging evidence on conservation such as the badger culling trial.	17

Genetics, Populations, Evolution and Ecosystems is 125 of the 1,977 questions in the guide.Get the guide, £8

How the guide is worked

Answering a question from memory stores it far better than reading the answer again. The guide runs that as a fixed procedure on one subtopic at a time, about twenty minutes a session.

Step 1 · Closed book
Cover the answers. Work through one subtopic and write down what you can. Leave blanks where you have nothing.
Step 2 · Open book
Go back to the top. Read each printed answer and write it out in full, including the ones you had right.
Step 3 · Closed book again
Same questions, same order, from memory. The gap between pass one and pass three is the session result.

Read the full method, the return schedule and the research behind it.