<P> 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 heritable traits of a population over time . Charles Darwin popularised the term "natural selection", and compared it with artificial selection . </P> <P> Variation exists within all populations of organisms . This occurs partly because random mutations arise in the genome of an individual organism, and offspring can inherit such mutations . Throughout the lives of the individuals, their genomes interact with their environments to cause variations in traits . The environment of a genome includes the molecular biology in the cell, other cells, other individuals, populations, species, as well as the abiotic environment . Individuals with certain variants of the trait may survive and reproduce more than individuals with other, less successful, variants; therefore, the population evolves . Factors that affect reproductive success are also important, including sexual selection (now often included in natural selection) and fecundity selection . </P>

Who figured out the mechanism of evolution known as natural selection