What is evolution, and who was Darwin? (spec 3.38)
Evolution = gradual change in a species over time; Darwin explained how it happens.
Evolution is the gradual change in the characteristics of a species (a population of organisms) over a very long time — usually many thousands or millions of years.
The big question scientists asked was: how does a species change? In 1859 Charles Darwin published his answer in a book called On the Origin of Species. His explanation is the theory of evolution by natural selection.
The word "theory" here does not mean "a guess". In science a theory is a well-tested explanation that is supported by a huge amount of evidence (fossils, the way living things are related, and modern DNA studies). Natural selection is the mechanism — the engine — that drives evolution.
The key idea is simple but powerful: nature "selects" which individuals survive and breed. Individuals that are better suited to their environment leave more offspring, so their useful features are passed on. Over many generations this slowly changes the whole population.
Exam tip. If a question asks who proposed natural selection, the answer is Charles Darwin. If it asks what natural selection produces, the answer is evolution (a change in the species over time).
- Evolution = gradual change in a species over a long time.
- Charles Darwin explained evolution by natural selection.
- Natural selection is the mechanism that causes evolution.
See the full worked example for darwin's theory of evolution by natural selection →