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All forms of natural speciation have taken place over the course of evolution; however, debate persists as to the relative importance of each mechanism in driving biodiversity. [ 26 ] One example of natural speciation is the diversity of the three-spined stickleback , a marine fish that, after the last glacial period , has undergone speciation ...
A prerequisite for natural selection to result in adaptive evolution, novel traits and speciation is the presence of heritable genetic variation that results in fitness differences. Genetic variation is the result of mutations, genetic recombinations and alterations in the karyotype (the number, shape, size and internal arrangement of the ...
In this theory, speciation and rapid evolution are linked, with natural selection and genetic drift acting most strongly on organisms undergoing speciation in novel habitats or small populations. As a result, the periods of stasis in the fossil record correspond to the parental population and the organisms undergoing speciation and rapid ...
Speciation is the process in which populations within one species change to an extent at which they become reproductively isolated, that is, they cannot interbreed anymore. However, this classical concept has been challenged and more recently, a phylogenetic or evolutionary species concept has been adopted.
Reinforcement is the process by which natural selection reinforces reproductive isolation. In sympatry, reinforcement increases species discrimination and sexual adaptation in order to avoid maladaptive hybridization and encourage speciation. If hybrid offspring are either sterile or less-fit than non-hybrid offspring, mating between members of ...
The idea of evolution by natural selection was proposed by Charles Darwin in 1859, but evolutionary biology, as an academic discipline in its own right, emerged during the period of the modern synthesis in the 1930s and 1940s. [8] It was not until the 1980s that many universities had departments of evolutionary biology.
Darwinism subsequently referred to the specific concepts of natural selection, the Weismann barrier, or the central dogma of molecular biology. [2] Though the term usually refers strictly to biological evolution, creationists have appropriated it to refer to the origin of life or to cosmic evolution, that are distinct to biological evolution, [3] and therefore consider it to be the belief and ...
Geographic and natural elements may likewise add to these cycles and lead to examples of hereditary variety, such as genetic differences that cause genetic isolation. [3] Genetic variations are often unequally distributed over a species' geographic distribution, with differences between populations at the geographic center and the range's ...