THE UNITS OF SELECTION

摘要: The principle of natural selection as the motive force for evolution was framed by Darwin in terms a "struggle existence" on part organisms living finite and risky environment. logical skeleton his argument, however, turns out to be powerful predictive system changes at all levels biological organization. As seen present-day evo­ lutionists, Darwin's scheme embodies three principles (Lewontin 1) : 1. Different individuals popUlation have different morphologies, physiologies, behaviors (phenotypic variation). 2. phenotypes rates survival reproduc­ tion environments (differential fitness). 3. There is correlation between parents offspring contribu­ each future generations (fitness heritable). These embody selec­ tion. While they hold, population will undergo evolutionary change. It important note certain generality principles. No particular mechanism inheritance specifi'ed, but only fitness parent offspring. would evolve whether arose from Mendelian, cytoplasmic, or cultural inheritance. Conversely, when equilibrium under (for example, stable polymorphism due heterozygous superiority), there no offspring, matter what Nor does Principle 2 specify reason differential rate contribution phenotypes. not necessary, that resources short supply struggle existence. himself pointed "a plant edge desert said life against drought." Thus, although came idea consideration Malthus', essay overpopulation, element competition resource integral argument. Natural occurs even two bacterial strains are growing logarithmically an excess nutrient broth if division times. means any enti­ ties nature variation, reproduction, heritability may evolve. For we replace term individual with