Natural selection is the mechanism by which heritable variation leads to differential survival and reproduction in changing environments in evolving populations.
Coverage 2012–2025 · Updated 16 Jul 2026
Natural selection is the process in which heritable trait differences cause some individuals to leave more surviving offspring than others.
Selection pressure changes success; successful individuals pass alleles more often; across generations the population’s trait and allele frequencies shift.
Trace variation; pressure; survival or mating; offspring; population change.; separate variation, selection, inheritance and time
In a dry habitat, beetles whose colour better matches the soil are eaten less and leave more offspring, so camouflage becomes more common. This gives a concrete prediction from the stated population.
Individuals do not evolve because they need to; selection changes inherited variation already present. Interpret the result within the stated selection model and evidence limits.
This objective is assessed through essay response, commonly using Explain / Identify / Evaluate.
Explain / Identify / Evaluate / Outline / State / Describe / Discuss
Build the answer around this relationship: Natural selection acts on individuals but changes populations across generations.
Representative question
Explain how evolution may happen in response to environmental change with evidence from examples.
Core D4.1 examples follow the same causal route: heritable variation exists, a selection pressure acts, individuals differ in fitness, and alleles linked to higher reproduction become more common. Endler’s guppies and sexual selection are evidence versions of the same chain.
Core natural-selection exam answers should never stop at “the best adapted survive.” They need the chain: heritable variation exists, a named pressure acts, some individuals have higher fitness, and their alleles become more common over generations. Use this for abiotic pressure, overproduction, sexual selection, and Endler-style data.
