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Disruptive selection is a specific type of natural selection that actively selects against the intermediate in a population, favoring both extremes of the spectrum. Disruptive selection is inferred to oftentimes lead to sympatric speciation through a phyletic gradualism mode of evolution. Disruptive selection can be caused or influenced by ...
The uncommon disruptive selection also acts during transition periods when the current mode is sub-optimal, but alters the trait in more than one direction. In particular, if the trait is quantitative and univariate then both higher and lower trait levels are favoured. Disruptive selection can be a precursor to speciation. [57]
[1] [5] The quadratic regression (γ) is the selection gradient, ω is the fitness of a trait value z, and α is the y-intercept of the fitness function. Here, individuals with intermediate trait values may have the highest fitness (stabilizing selection) or those with extreme trait values may have the highest fitness (disruptive selection).
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 ...
Another example of directional selection is the beak size in a specific population of finches. Darwin first observed this in the publication of his book, On the Origin of Species , and he details how the size of the finches beak differs based on environmental factors.
In evolutionary biology, sympatric speciation is the evolution of a new species from a surviving ancestral species while both continue to inhabit the same geographic region. In evolutionary biology and biogeography, sympatric and sympatry are terms referring to organisms whose ranges overlap so
An example of gametic isolation involves the allopatric sea urchins have minimal bindin differences (bindin is a protein involved in the process of sea urchin fertilization, used for species-specific recognition of the egg by the sperm) and have insufficient barriers to fertilization.
Edward Bagnall Poulton's 1890 book, The Colours of Animals, renamed Wallace's concept of warning colours "aposematic" coloration, as well as supporting Darwin's then unpopular theories of natural selection and sexual selection. [18] Poulton's explanations of coloration are emphatically Darwinian. For example, on aposematic coloration he wrote that