Geographic isolation, or allopatry, is a term used in the study of evolution. When part of a population of a species becomes geographically isolated from the remainder, it may over time evolve characteristics different from the parent population (due to natural selection). This is particularly likely to happen if the isolated population is small, because of founder effects, or if the population become isolated in an environment which makes new demands upon it. A lot of reasearch has shown that this is a huge reason why there are so many different species throughout the world. This article is about evolution in biology. ... In biology, a species is one of the basic units of biodiversity. ... Simple illustration of founder effect. ...

If there is sufficient genetic change following geographical isolation, then if the geographical barriers are removed (perhaps due to human activity), members of the two populations will be unable to successfully mate with each other. At this point, a new species has emerged. Geographical isolation is thus a key factor in speciation, the formation of new species - also termed allopatric speciation. For a non-technical introduction to the topic, please see Introduction to genetics. ... Charles Darwins first sketch of an evolutionary tree from his First Notebook on Transmutation of Species (1837) Speciation is the evolutionary process by which new biological species arise. ... Allopatric speciation, also known as geographic speciation, occurs when populations physically isolated by an extrinsic barrier evolve intrinsic (genetic) reproductive isolation such that if the barrier between the populations breaks down, individuals of the two populations can no longer interbreed. ...

However, it is more common for there to be considerable genetic and phenotypic change without the loss of the capacity for interbreeding - interbreeding is simply prevented by the geographical separation of populations. In this case the populations are normally regarded as subspecies. For a non-technical introduction to the topic, please see Introduction to genetics. ... Individuals in the mollusk species Donax variabilis show diverse coloration and patterning in their phenotypes. ... In zoology, as in other branches of biology, subspecies is the rank immediately subordinate to a species. ...

The African Elephant for instance has always been regarded as a single species. Because of morphological and DNA differences some scientists classify the elephants into three subspecies. Researchers at the University of California, San Diego (UCSD) have argued that divergence due to geographical isolation has gone further, and the elephants of West Africa should be regarded as a separate species from either the savanna elephants of Central, Eastern and Southern Africa, or the forest elephants of Central Africa. Species Loxodonta adaurora (extinct) Loxodonta africana Loxodonta cyclotis African elephants are the two species of elephants in the genus Loxodonta, one of the two existing genera in Elephantidae. ... The structure of part of a DNA double helix Deoxyribonucleic acid (DNA) is a nucleic acid that contains the genetic instructions for the development and function of living organisms. ... In zoology, as in other branches of biology, subspecies is the rank immediately subordinate to a species. ... The University of California, San Diego (popularly known as UCSD, or sometimes UC San Diego) is a public, coeducational research university located in La Jolla, a seaside resort community of San Diego, California. ...  Western Africa (UN subregion)  Maghreb[1] West Africa or Western Africa is the westernmost region of the African continent. ... Savanna at Ngorongoro Conservation Area, Tanzania. ...

Other cases arise where two populations that are quite distinct morphologically, and are native to different continents, have been classified as different species; but when members of one species are introduced into the other's range, they are found to interbreed freely, showing that they were in fact only geographically isolated subspecies. This was found to be the case, for example, when the Mallard Anas platyrhynchos was introduced into New Zealand; it interbred freely with the native Grey Duck, which had been classified as a separate species, Anas superciliosa; it is controversial whether its specific status can now be retained. It is also James DaVaughn McFadden Animated, colour-coded map showing the various continents. ... Binomial name Anas platyrhynchos Linnaeus, 1758 Subspecies See Mexican Duck, Anas, and article text The Mallard (Anas platyrhynchos[1]), also known as the wild duck, is a dabbling duck which breeds throughout the temperate and sub-tropical areas of North America, Europe, Asia, and Australia. ... Binomial name Anas superciliosa Gmelin, 1789 Subspecies (New Zealand Grey Duck) (Australasian Duck) (Island Black Duck) The Pacific Black Duck, Anas superciliosa is a dabbling duck found in much of Indonesia, New Guinea, Australia, New Zealand, and many islands in the southwestern Pacific, reaching to the Caroline Islands in the...