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
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.
Which way do arrows point in a food chain?✗ From predator to prey, because predators eat prey. ✓ From prey to predator, showing the direction of energy flow.
Is energy recycled in an ecosystem?✗ Yes, the same energy goes round and round forever. ✓ No — energy flows through and is lost as heat; only nutrients are recycled.
Why are decomposers important?✗ They are not important and could be removed. ✓ They recycle nutrients from dead matter back into the ecosystem.
Practise Evolution & Biodiversity — free games
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