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Natural selection

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Theory of Evolution > Selection > Natural Selection

Diagram of natural selection (directional) selecting darker organisms over lighter ones.

Natural selection is the idea that traits which give a reproductive advantage on their possessors tend to spread throughout a given population, and traits which are reproductively disadvantageous tend to disappear.

Natural selection was recognized as a mechanism for evolution by Charles Darwin and independently by Alfred Russel Wallace. Herbert Spencer soon afterwards coined the somewhat misleading term "Survival of the fittest".



Natural selection is technically defined as 'the differential reproductive success of genetic variants'. Variation exists in phenotype, due in part to variation in genotype caused by factors such mutation and sexual reproduction. For example, not all trees grow to the same height, due both to the variations in rain patterns and the variation in the genes of the plants.

Some of these variations confer a reproductive advantage to the organism in certain environments. In the case of the trees, those which grow taller may receive more light than those that are shorter, and so the taller trees have more energy to spend producing seeds. The increased success of being taller and the disadvantage of being shorter is an example of what is termed a "selection pressure" (despite not being a physical force or pressure).

Because some of the variation in inheritable, being contained the DNA of the organism, it can be passed on to the next generation. Those genes that gave an advantage to the possessor will be more likely to be passed on, as the organism is more likely to reproduce. Those genes that didn't give an advantage may not be passed on as often, as the organism possessing those genes is more likely to fail to reproduce. Therefore, the next generation should have a higher proportion of taller trees. That is, greater height has been 'selected for'.

See also

External Links

  1. Hoekstra et al. (2001). "Strength and tempo of directional selection in the wild." Proceedings of the National Academy of Sciences, Vol. 98, Issue 16, 9157-9160.
  2. Kingsolver et al. (2001) "The Strength of Phenotypic Selection in Natural Populations." American Naturalist, Vol. 157, pp. 245-261.
  3. Endler, John (1986). Natural Selection in the Wild. Princeton University Press.
  4. Mousseau, Timothy A., and Sinervo, Barry, eds. (1999). Adaptive Genetic Variation in the Wild. Oxford University Press.

  1. Mitton, Jeffry B. (1997). Selection in Natural Populations. Oxford University Press.

Creationist arguments about natural selection

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