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This is largely because the results of disruptive selection are less stable than the results of directional selection (directional selection favors individuals at only one end of the spectrum). For example, let us take the mathematically straightforward yet biologically improbable case of the rabbits: Suppose directional selection were taking ...
However, it is possible for directional selection to take a very long time to find a local optimum on a fitness landscape. [30] A possible example of long-term directional selection is the tendency of proteins to become more hydrophobic over time, [31] and to have their hydrophobic amino acids more interspersed along the sequence. [32]
Stabilizing selection is the most common form of nonlinear selection (non-directional) in humans. [13] There are few examples of genes with direct evidence of stabilizing selection in humans. However, most quantitative traits (height, birthweight, schizophrenia) are thought to be under stabilizing selection, due to their polygenicity and the ...
The first is directional selection, which is a shift in the average value of a trait over time—for example, organisms slowly getting taller. [80] Secondly, disruptive selection is selection for extreme trait values and often results in two different values becoming most common, with selection against the average value. This would be when ...
Selection can be divided into three classes, on the basis of its effect on allele frequencies: directional, stabilizing, and disruptive selection. [102] Directional selection occurs when an allele has a greater fitness than others, so that it increases in frequency, gaining an increasing share in the population.
The first and most common function to estimate fitness of a trait is linear ω =α +βz, which represents directional selection. [1] [10] The slope of the linear regression line (β) is the selection gradient, ω is the fitness of a trait value z, and α is the y-intercept of the fitness function.
According to the New York Times, here's exactly how to play Strands: Find theme words to fill the board. Theme words stay highlighted in blue when found.
Compared to examples of overdominance in actual populations, underdominance is considered more unstable [3] [4] and may lead to the fixation of either allele. [ 1 ] [ 5 ] [ 6 ] An example of stable underdominance may occur in individuals who are heterozygotic for polymorphisms that would make them better suited for one of two niches . [ 7 ]