Speciation

598 Words Mar 2nd, 2016 3 Pages
Speciation
Speciation is known to take place in two general ways. Species are known to change over time into something that is so extremely different they are considered a completely different species. In other words, a species can change so drastically that it splits into two separate groups that no longer share a similar gene pool. In each case of speciation, reproductive isolation occurs. Even for a single definition of species, there are many ways for speciation to occur. Under the biological species concept, speciation is the evolution of one or more reproductive isolating mechanisms. Under the cohesion species concept, speciation is the evolution of isolation or otherwise distinct reproductive communities and/or the evolution of
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When a normal organism contains two chromosomes (diploidy), there new offspring contain four chromosomes (tetraploidy). This creates reproductive isolation because a diploid organism is unable to mate with a tetraploid organism (Stebbins Jr., n.d.). Since sympatric speciation is uncommon, it occurs in plants because they generally fertilize themselves. Tetraploidy plants can reproduce with other tetraploidy plants of the opposite sex, allowing them to form a new species.
Allopatric speciation is a more common type of speciation, and this occurs when the species become isolated geographically. Once populations gap, or separate, the gene flow becomes nonexistent. The two populations that were separated become genetically different over time, due to natural selection in the different regions. However, if the species population is small, enough they can experience something known as the founder effect. Meaning the genetic diversity is reduced in the population due to the lack of a large variety of ancestors (Lemmon, n.d.). Because the two populations are separated by geography, genetic drift and natural selection will influence each population differently. Over time, this will create two genetically different species.
Natural selection plays an important role on the creation of new species, as well as allopatric speciation and sympatric speciation. Each of which plays a major