natural selection

selection /se·lec·tion/ (sĕ-lek´shun) the play of forces that determines the relative reproductive performance of the various genotypes in a population.

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directional selection  selection favoring individuals at one extreme of the distribution.

disruptive selection , diversifying selection selection favoring the two extremes rather than the intermediate.

natural selection  the survival in nature of those individuals and their progeny best equipped to adapt to environmental conditions.

sexual selection  natural selection in which certain characteristics attract male or female members of a species, thus ensuring survival of those characteristics.

stabilizing selection  selection favoring intermediate phenotypes rather than those at one or both extremes.

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natural selection

n.

The process in nature by which, according to Darwin's theory of evolution, only the organisms best adapted to their environment tend to survive and transmit their genetic characters in increasing numbers to succeeding generations while those less adapted tend to be eliminated.

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natural selection,

the natural evolutionary processes by which the organisms that are best adapted to an environment tend to survive and propagate whereas those that are unfit are less likely to do so. Compare artificial selection.

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natural

occurs in nature, without the intervention of humans.

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natural experiments

occur by chance when all variables for a population are constant except one, which is different for one large part of the population compared with the other, e.g. when half of a flock comes from one climate and the other half is a local resident in another climate.

natural focus

the ecology that is best suited to a biological system, e.g. an individual insect-borne disease; the area in which the disease naturally flourishes best; an ecological niche.

natural history

history of a process or organism as it occurs in nature, e.g. course of a disease from infection to resolution.

natural killer (NK) cell

see natural killer cell.

natural selection

selection occurring in nature, without any human intervention, direct or indirect.

natural ventilation

ventilation without the use of artificially induced energy and the machines which it drives; the forces used are wind and the exchange of heat from within the barn and the external air, controlled by ventilation devices in the walls and the ceiling.