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According to Radolf and Samuels (2010), evolution is a change of a population’s gene pool within a given period of time. The two scholars noted that this change is majorly driven by four different forces. These include; natural selection, genetic drift, migration and mutation. This write up seeks to describe how each of the four forces of evolution impact on variation within a population as well as between populations. In addition it will also give an illustration of an isolating mechanism and how it creates a situation leading to speciation.
Copy (2007) identified the major force as natural selection. He argued that this is the force behind the differences that exist in the levels of reproduction. Its results are heritable and therefore passed from one living thing to another within and between populations. For example, organisms that are able to survive and produce more offspring are normally favored while those who can not adopt and reproduce are eliminated.
The second evolutional force is mutation which causes variations that allow the natural selection to work. Krawetz (2009) noted that mutation is the force that is responsible or the copying of genetic material. He added that any problem that arises during mutation can lead into genetic variations which will in turn have an effect on the adaptability of the resulting species. It therefore results into a totally new genetic material and therefore new species.
The third force is the genetic thrift which is basically a process by which the genetics of a population undergoes a random change. In his illustrations, Russell (2011) notes that in a case where a large number of large squirrels circum to death following a forest fire than their small squirrel counterparts, the ratio of their population in that ecosystem will change causing necessity for adjustments to prevent elimination. Its effect is purely on a random chance. This force therefore instead of creating new genetic materials, changes the ratios of the initial genes a process that is normally drastic.
The forth is the migration force which results from migration of organisms. Tibayrenc (2007) noted that normally, the migrating individuals introduce their genes to the new ecosystem causing alterations in the populations’ genetic layout. Strickberger (2000) added that even though migration can neither create new genetic material nor destroy the initially existing material, it can potentially cause the shuffling of the initially existing material leading to the adjustment of the initial material/population ratios.
In conclusion, it is therefore clear that natural selection is the major evolution force. However, its effect is influenced by the other three evolution forces.