natural selection defined in 1951 yearnatural selection - natural selection;
natural selection - The principal mechanism of evolutionary change, originally suggested by Darwin in 1859. The theory that evolution occurs by natural selection asserts that, of the range of different individuals which make up the population of a given species, individuals having certain characteristics contribute more offspring to the succeeding generation than those having other characteristics; and if such characteristics have an inherited basis, the composition of the population is thereby changed. If one considers the zygotes produced within a population of a species, usually only a minority will develop to maturity and still fewer will succeed in producing offspring. Within such a population there is always variation between individuals. The theory of natural selection asserts that the contribution of offspring to the next generation is not entirely random, but is correlated with this variability. Some kinds of variant individual are consistently more successful in leaving offspring than other kinds. The successful variants and their progeny are said to be Selected', by a natural process. In other words different variations have different 'survival value' in the face of the hostile circumstances in which all organisms live. Of these variations, only those which are inherited are important for evolution. Natural selection is thus the main agent controlling the composition of a population during the course of time, eliminating certain variants and thus preventing change in some directions, making other variants more prevalent and hence producing evolutionary change in other directions.
near natural selection in Knolik
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