selection (redirected from Directional selection)

selection /se·lec·tion/ (se-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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se·lec·tion (s-lkshn)

n.

A natural or artificial process that favors or induces survival and perpetuation of one kind of organism over others that die or fail to produce offspring.

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selection,

n 1. the act of choosing between or among a variety of options or alternatives.
2. the process by which various factors or mechanisms determine and modify the reproductive ability of a genotype within a specific population. Also referred to as
natural selection.

selection, shade (tooth color selection),

n the determination of the color (hue, brilliance, saturation, translucency) of the artificial tooth or set of teeth for a given patient.

selection, tooth,

n the selection of a tooth or teeth (shape, size, color) to harmonize with the individual characteristics of a patient.

selection, tooth color,

n See selection, shade.

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selection

1. choosing the individual units to be included in a sample. See also random selection.

2. choosing the animals to be retained for breeding purposes; genetic selection.

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artificial selection

selection based on human decisions.

selection coefficient

proportionate reduction in the average genetic contribution made by a specific genotype, relative to the contribution made by another genotype. Denoted by s.

selection criteria

the animal characteristic which is used in a selection program.

selection differential

a measure of the gain achieved by selection; the phenotypic superiority of selected individuals, compared to the population from which they were selected.

selection index

a single overall estimate of the patient's true breeding value obtained from as many sources of information as are available.

individual selection

selection on the results of performance testing of the subject.

selection intensity

the superiority of the individuals selected for breeding, relative to the population from which they were selected.

selection limit

the situation in which the entire population is homozygous for the same set of favorable genes; called also selection plateau.

selection/mutation balance

when the rate of removal of a gene from the population by selection equals the rate at which mutations occur.

selection plateau

see selection limit.

selection program

the method used to select individuals from a population to be used for breeding. Usually includes nomination of the characters to be selected, the optimum size of the population in which the program is to operate, the intensity of selection available, the accuracy of the selection procedures, lengths of the generations in the species, the target rate of response.