A-Level Biology: Evolution & Biodiversity Revision

Quick check · one tap

How does a population of organisms become better adapted to its environment over time?

Evolution & Biodiversity is a core part of A-Level Biology. Revise the key concepts and common mistakes below, then lock them in with the free games.

Key concepts

VariationDifferences within a species (genetic and environmental).

Natural selectionBetter-adapted individuals survive and reproduce.

EvolutionChange in a population over generations.

AdaptationFeatures that improve survival.

SpeciationFormation of new species.

ClassificationGrouping organisms by shared, evolutionary features.

Gene poolAll alleles of all genes in a population

Allele frequencyProportion of one allele in the gene pool

Hardy-WeinbergModel: allele frequencies stay constant if no selection, drift, migration, mutation

p + q = 1Two allele frequencies must sum to one

p^2 + 2pq + q^2 = 1Genotype frequencies: homozygous dominant + heterozygous + homozygous recessive

Five HW assumptionsNo selection, no migration, no mutation, random mating, large population

SpeciesGroup of organisms that can interbreed to produce fertile offspring

Allopatric speciationNew species arises by geographic isolation

What your exam board covers

Where Evolution & Biodiversity sits in each exam board's specification. Tap a board to see what it lists.

EdexcelBiodiversitySpec 9BI0

Part of: Classification and biodiversity

Source: Pearson Edexcel A-Level Biology B (9BI0) specification, accessed 23 June 2026.

OCRModule 4 — Biodiversity, evolution and diseaseSpec H420

Communicable diseases, disease prevention and the immune system
Biodiversity
Classification and evolution

Source: OCR A Level Biology A (H420) specification, accessed 23 June 2026.

Learn Evolution & Biodiversity step by step

Free interactive mini-lessons: short screens, worked examples and quick checks. Pick your exam board:

Other boards:AQA CCEA Eduqas/WJEC

Common mistakes to avoid

Questions where students often pick the tempting wrong answer — make sure you know the right one:

How does a population of organisms become better adapted to its environment over time?✗ Individual organisms change during their lifetime in response to their environment and pass the changes on to offspring. ✓ Individuals with advantageous heritable variations survive and reproduce more; their alleles increase in frequency over generations.

What actually changes during natural selection in a population?✗ Individual organisms change their own genes to adapt. ✓ The frequencies of alleles in the population's gene pool change across generations.

Practise Evolution & Biodiversity — free games

Test yourself with these quick revision games for this topic:

▶ Two Truths, One Lie ▶ Reveal Race ▶ Connections Grid ▶ Falling Words ▶ Word Web

See all 22 games in the Revision Arcade →

Evolution & Biodiversity

Key concepts

What your exam board covers

Common mistakes to avoid

Practise Evolution & Biodiversity — free games

More A-Level Biology topics