Selection that acts to eliminate the intermediate phenotypes is called disruptive selection. Gradualism describes evolutionary change as occurring slowly over long periods of time. Darwin predicted that the environment is the driving force for speciation, therefore, an organisms ability to adapt and change according to environmental conditions leads to the appearance of new kinds of organisms. A sexually reproducing species consists of one or more populations of individuals that are reproductively isolated from other such populations, and can interbreed under natural conditions and produce fertile offspring. Populations of a species have a shared genetic history and are evolving independently of other species.
Speciation is the process where daughter species evolve from the parental species.
Mutation, natural selection, and genetic drift operate independently in each population and favors genetic divergence. This site created by Dr. Sandra Landuyt of Penn Valley Community College as part of a Title III educational grant. It was later modified by Terry Davin as part of a modification of the general biology course at Penn Valley.