- (anthropology) changes in gene frequencies resulting from selective pressures being placed upon a population by environmental factors; results in a greater fitness of the population to its ecological niche. Source: Anthromorphemics
- becoming fitted to an environment, or the mutual fitness of an organism and its environments Source: Noland, George B. 1983. General Biology, 11th Edition. St. Louis, MO. C. V. Mosby
- The acquiring of characteristics by an organism (or group of organisms) which make it better suited to live and reproduce in its environment.
- A peculiarity of structure, physiology, or behavior of an organism which especially aids in fitting the organism to its particular environment. Source: Curtis, Helena. 1968. Biology. New York, NY. Worth Publishers