Natural selection is the differential survival and reproduction of individuals due to differences in phenotype. It is a key mechanism of evolution, the change in the heritable traits characteristic of a population over generations.

Darwinism is a term used to describe a theory of biological evolution developed by the English naturalist Charles Darwin (1809–1882) and others. The theory states that all species of organisms arise and develop through the natural selection of small, inherited variations that increase the individual's ability to compete, survive, and reproduce.

Learn about how natural selection works at the level of genes, alleles, genotypes, and phenotypes.

natural selection, process that results in the adaptation of an organism to its environment by means of selectively reproducing changes in its genotype, or genetic constitution. A brief treatment of natural selection follows. For full treatment, see evolution: The concept of natural selection.

In natural selection, genetic mutations that are beneficial to an individual’s survival are passed on through reproduction. This results in a new generation of organisms that are more likely to survive to reproduce.