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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 ...
Evolutionary biology is the subfield of biology that studies the evolutionary processes such as natural selection, common descent, and speciation that produced the diversity of life on Earth.
Evolution is the change in the heritable characteristics of biological populations over successive generations. [1] [2] It occurs when evolutionary processes such as natural selection and genetic drift act on genetic variation, resulting in certain characteristics becoming more or less common within a population over successive generations. [3]
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.
Genome recombination results in speciation of the two populations, with an additional hybrid species. All three species are separated by intrinsic reproductive barriers [ 1 ] Secondary contact is the process in which two allopatrically distributed populations of a species are geographically reunited.
This process of speciation influenced by natural selection is reinforcement, and can happen under any mode of speciation [3]: 355 (e.g. geographic modes of speciation or ecological speciation [21]). It necessitates two forces of evolution that act on mate choice: natural selection and gene flow. [22]
In biology, two closely related species or populations are considered sympatric when they exist in the same geographic area and thus frequently encounter each other. [1] An initially interbreeding population that splits into two or more distinct species sharing a common range exemplifies sympatric speciation .