Natural Selection

Reproductively successful individuals are able to pass on their alleles to their offspring and the population will continue to have these alleles in the gene pool. Differences in the reproductive success of the alleles affects the allele frequency in a population.Within any population there is a gene pool of a variety of alleles.Random mutation occurs by chance and usually leads to harmful alleles but may lead to an allele that gives the individual a competitive advantage over the rest of the population under certain conditions or in certain environments.These individuals will be better adapted to the environment and will outcompete the other members of the species. They will be able to gain resources to grow more rapidly, live longer and breed more successfully than the other members of the species.The individuals with the advantageous alleles will survive, reproduce and pass on their advantageous alleles to their offspring. Over many generations the allele frequency will increase.The environment provides the selection pressure, without which the individuals would have no competitive advantage or reproductive success.