a type of natural selection in an animal or plant population resulting in the appearance of two or several new forms from a single inceptive one. For example, in the absence of food necessary for the growing young of perch, that is, the fingerlings of other fish, there may remain only “dwarfs” (individuals with severely retarded growth, who may feed for a long time on plankton crustaceans) and “giants” (individuals capable by the end of their first year of feeding on fingerling perch of their own generation). As a result of disruptive selection, in a number of years genetically conditioned races of giants and dwarfs are formed in a body of water.