Natural selection represents a crucial mechanism of evolution. It acts on the phenotype of organisms resulting in increased reproductive fitness of the carriers of advantageous phenotypes in the given environment and vice versa. So, the alleles underlying relatively disadvantageous phenotypes are gradually removed from the population.
Depending on the favored phenotype, we can distinguish
- directional selection (one phenotype extreme is favored)
- stabilizing selection (intermediate phenotype is favored)
- disruptive selection (both phenotype extremes are favored)
Together with Genetic drift, natural selection is considered one of the major driving forces of the biological evolution.