Short answer
Evolution is change in inherited characteristics of a population over generations. Natural selection is one way that change occurs: inherited traits associated with greater reproductive success tend to become more common in a given environment. Mutation, drift and gene flow can also contribute to evolution. 1 2
Natural selection is one mechanism of evolution; evolution is the broader pattern or process of population change.
On this page
At a glance
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| Question | Natural selection | Evolution |
|---|---|---|
| Role | Mechanism | Broader population change |
| Requires advantage? | Depends on differential reproductive success | No; change can be neutral |
| Example | Resistance-associated variants spread under drug exposure | Allele frequencies change over generations |
The table summarizes the cited definitions and the article’s stated scope. 1 2
What each thing is
Natural selection. A process in which heritable differences associated with survival or reproduction change in frequency across generations. 1
Evolution. Change in heritable characteristics of populations across generations. 2
Key differences
Natural selection is directional with respect to reproductive success in a particular environment; evolution need not be adaptive. Genetic drift can alter allele frequencies by chance, and migration can introduce variants. Selection acts on existing variation while mutation can generate new variation. 1 2
To identify selection, compare inherited differences and their effects on the number of descendants in a particular setting. If one variant becomes common merely because a few carriers happened to found an isolated group, the population has evolved by drift. The same observed change in frequency can therefore have different causal stories. 1 2
How to tell them apart
If a statement explains why some heritable variants leave more descendants than others, it is about natural selection. If it reports that inherited traits or allele frequencies changed across generations, it is about evolution, regardless of cause. 1 2
Where they overlap
Natural selection often produces evolutionary change. The two terms can appear in the same explanation when both the mechanism and the outcome are specified. 1 2
Edge cases
An individual growing stronger during life is not population evolution. Selection can favor traits in one setting and not another, and an evolutionary change can happen without an improvement or plan. 1 2
Selection does not create the variant it favors at the moment it is needed; new variation can arise through mutation and enter through migration. It also has no fixed direction across environments. A trait favored under one set of conditions can become costly when conditions change. 1 2
Why the distinction exists
The separation lets biologists ask two different questions: did a population change, and what process caused the change? Conflating them hides alternatives such as drift. 1 2
Common misconceptions
Evolution does not always mean progress, and natural selection does not anticipate what a species will need in the future. 1 2
Examples
In a small isolated population, an allele could become common by chance: evolution occurred even if natural selection did not drive that particular change. 1 2
Sources
Sources checked October 3, 2026.
- OpenStax Biology 2e — Adaptive Evolution. 19.3 Adaptive Evolution.
- OpenStax Biology 2e — Understanding Evolution. 18.1 Understanding Evolution.