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A significant example of directional selection in populations is the fluctuations of light and dark phenotypes in peppered moths in the 1800s. [16] During the industrial revolution, environmental conditions were rapidly changing with the newfound emission of dark, black smoke from factories that would change the color of trees, rocks, and other ...
Even when an allele is selectively neutral, selection acting on nearby genes may also change its allele frequency through hitchhiking or background selection. While heterozygosity at a given locus decreases over time as alleles become fixed or lost in the population, variation is maintained in the population through new mutations and gene flow ...
Stabilizing selection (not to be confused with negative or purifying selection [1] [2]) is a type of natural selection in which the population mean stabilizes on a particular non-extreme trait value. This is thought to be the most common mechanism of action for natural selection because most traits do not appear to change drastically over time ...
These charts depict the different types of genetic selection. On each graph, the x-axis variable is the type of phenotypic trait and the y-axis variable is the amount of organisms. Group A is the original population and Group B is the population after selection. Graph 1 shows directional selection, in which a single extreme phenotype is favored.
The level of gene flow among populations can be estimated by observing the dispersal of individuals and recording their reproductive success. [4] [11] This direct method is only suitable for some types of organisms, more often indirect methods are used that infer gene flow by comparing allele frequencies among population samples.
The evolution of the peppered moth is an evolutionary instance of directional colour change in the moth population as a consequence of air pollution during the Industrial Revolution. The frequency of dark-coloured moths increased at that time, an example of industrial melanism. Later, when pollution was reduced in response to clean air ...
In positive frequency-dependent selection the fitness of a phenotype increases as it becomes more common. In negative frequency-dependent selection the fitness of a phenotype decreases as it becomes more common. For example, in prey switching, rare morphs of prey are actually fitter due to predators concentrating on the more frequent morphs. As ...
Directional statistics (also circular statistics or spherical statistics) is the subdiscipline of statistics that deals with directions (unit vectors in Euclidean space, R n), axes (lines through the origin in R n) or rotations in R n.
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