Allopatric Speciation
Speciation occurs when an individual member of a particular species develops many other different genetic features to a point where they cannot mate with the original species and be able to produce a fertile offspring. This means that these creatures have become separate species and a good example is of horses and donkey. They a descended from a common ancestor, but their genetic makeup varies greatly. They are numerous types of speciation and they are allopatric speciation, parapatric, peripatric and sympatric speciation.
Allopatric speciation is one of the widely discussed and debated about types of speciation. It is a kind of speciation that occurs when biological populations of the same species become isolated from each other to an extent that prevents any genetic interchange. This kind of speciation occurs generally due to population dispersal leading to emigration or due to geographical changes such as island formation, mountain formation or large scale human activities such as agricultural and civil engineering developments.
The isolated or vicariant populations then go through genotypic or phenotypic divergence. Here, they become subjected to different choosy pressures, independently undergo scientific genetic drift or undergo different mutations arise in their population’s gene pools. Separate population overtime may evolve distinctively different features. However if all geographical barriers are later removed, members of the involved two populations may be unable to fruitfully mate with each other.
This will lead to genetically isolated groups which emerge has different species. All in all, allopatric isolation is a key determinant of speciation and a common process through which new species arise. From the legendary naturalist and geologist Charles Darwin observation adaptive radiation is a consequence of allopatric speciation among many island populations. Allopatric speciation is all about organisms whose range are entirely separate and do not occur in any one place together. In a sense, these organisms are closely related, but separation may be attributed to either geological processes or population dispersal.
Geological processes have had great impact in allopatric speciation. These processes can fragment a population through events such as emergence of mountain ranges, glacial processes, formation or destruction of land bridges or canyon formation can all lead to speciation. Plate tectonics are core factors leading to separation of populations and distinctive distribution of species. Many times, when populations become genetically isolated, heritable variations may accumulate so that they can easily become different from parental population. With time, these variations may lead to reproductive isolation.
Allopatric speciation is the most dominant forms of speciation and there are numerous ways that it can be depicted. For example, the African elephant has been regarded as a single species, but because of morphological and DNA differences, some scientists classify them into two subspecies. Elephants of the West Africa should be classified as a spate species from both the savanna elephants of the central, southern and eastern Africa and the forest elephants of the central Africa. Most of the allopatric speciation occurred in the past and many organisms have been featured in most studies. Scientist can invariably isolate when the events occurred and continue to study how they happened for more credible information.
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Sources
http://www.pbs.org/wgbh/evolution/library/05/2/l_052_03.html
http://en.wikipedia.org/wiki/Allopatric_speciation
http://www.sparknotes.com/biology/evolution/speciation/section2.rhtml