Bio B Tau - Glossary: Speciation (Less.7)

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Allopatric speciation

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the origin of two or more species resulting from divergent evolution of populations that are geographically isolated from one another.

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Allopatry

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geographical separation, such that members of two or more populations fail to encounter one another.

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Biological species concept

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The concept of species, according to which a species is a set of organisms that can interbreed among each other.

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Gene flow

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movement or sharing of genes within and between populations due to reproduction among members of the populations.

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Genetic variation

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differences in the DNA of the members of a population or species; genetic diversity.

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Hybrid

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The offspring of a cross between two species.

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Hybrid zone

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A geographical region in which members of different species meet and mate, producing offspring of mixed ancestry.

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Postzygotic isolation

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reproductive isolation that occurs after fertilization, such as hybrid sterility and hybrid inviability.

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Prezygotic isolation

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reproductive isolation that occurs before fertilization. Includes species differences in traits such as sexual behaviour, habitat preference, seasonal breeding (all premating), and gametic compatibility (postmating but prezygotic).

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Punctuated equilibria

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the view that speciation occurs relatively rapidly, and that virtually all evolution happens at speciation (cladogenesis), with long intervening phases of stasis of lineages.

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Punctuation

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a rapid speciation event, forming part of the model of evolution by punctuated equilibria.

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Reinforcement

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the adaptive strengthening of prezygotic isolating mechanisms in a zone of secondary contact between two distinct taxa that have previously evolved some postzygotic isolation. In this process, natural selection reduces gene flow between the taxa because hybridization is deleterious.

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Reproductive isolation

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absence (or severe restriction) of gene flow between populations whose members are in contact with one another.

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Secondary contact

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the co-occurrence in one area of two taxa that were previously geographically isolated and had accumulated some genetic divergence.

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Speciation

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the establishment of reproductive isolation between two or more previously interbreeding populations.

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Species

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A classificatory category, which can be variously defined by different species concept. The biological species concept, according to which a species is a set of interbreeding organisms, is the most widely used definition, at least by biologists who study vertebrates. A particular species is referred to by a Linnaean binomial, such as Homo sapiens for human beings.

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Sympatric speciation

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speciation occurring within a single geographical area, so that reproductive isolation arises between individuals that always have the opportunity to interbreed.

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Sympatry

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absence of geographical separation, such that all individuals have the same chance of meeting each other.