Natural selection
Exam-ready definition
The process by which individuals with variation better suited to the environment are more likely to survive and reproduce, passing on their alleles, so the favourable feature becomes more common over generations.
How this is marked
The 6-mark version is formulaic: variation exists → competition/selection pressure → best adapted survive → reproduce → pass on alleles → frequency increases over generations. Antibiotic resistance is the most commonly examined context.
In an exam answer
For antibiotic resistance: 'Resistant bacteria survive the antibiotic, reproduce and pass on the resistance allele, so over generations the resistant type becomes more common. This is natural selection.'
Full topic guide: Inheritance
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