– forces of nature/environment which act on gene pools of population of organisms
– ensures that gene which are disadvantageous to the organism eliminate
– only those genes that enable the organism to survive in an environment survive to reproductive maturity (survival of the fittest)
– this was proposed by Drawn as the major force in evolution of plants and animals
– he could not demonstrate this practically
– natural selection acts slowly on populations of organisms
– it perpetrate constancy as long as the environment remains stable
– promotes the emergence of new forms if and when the environment changes