Allopatric Speciation Is The Only Mechanism By Which New Species Arise Essay

Allopatric Speciation Is The Only Mechanism By Which New Species Arise - Essay Example Species: is defined by Mayr (1942, 1963) as quoted in Cowlishaw; Dunbar (2000: p.13), as a population of individuals capable of interbreeding, that is producing fertile offspring. According to Magurran et al (1999: p.2), Species is considered to be groups of populations reproductively isolated from other such groups by â€Å"isolating mechanisms†- genetically based traits that prevent gene exchange. Speciation: Brigatti; Martins and Roditi (2007: p.378) define Speciation as the process of the generation of two reproductively isolated populations, after which gene flow between the different taxa is absent in any form. That is, new species which are not capable of reproduction with each other are created as a result of speciation. According to the view of Evolutionary Biology, the creation of a new species comes about primarily through variation, the creation of mutants. These mutants might replace the parent species or live in a separate landscape, either way enhancing the competitive environment through a variety of phenotypes. The key to speciation lies in the elimination of inviable or maladaptive phenotypes, mutants of companies that are less successful (Dekkers, 2005: p.144). All populations of a species share a unique common ancestor and a gene pool. They can interbreed and produce fertile offspring under natural conditions. If and when gene flow between them stops, reproductive isolating mechanisms typically evolve. This is because, mutation, natural selection and genetic drift operate independently in each population. Such divergence may give rise to a new species (Starr; Evers, 2006: p.283). Mass extinctions, slow recoveries, and adaptive radiations are major macroevolutionary patterns. (Cowlishaw; Dunbar 2000: p.22) state that speciation in some groups has been dependent upon ecological release following the extinction of ecologically dominant species. Allopatric Speciation: Allopatric Speciation occurs when a geographical barrier cuts off