Even though the fundamental theoretical foundation for the understanding of evolution has been in existence for the past few centuries, the essential significance of this framework is still debatable (Ayala & Robert 182). By population genetics, four basic forces influence evolution processes. These forces are natural selection, genetic flow, mutation, and genetic drift. Through natural selection, the best-adapted organisms sire the desired offspring.
These offspring will carry forward to the next generations the desired genes passed on from their parents. Unlike natural selection, genetic drift is an unintentional process through which probability determines the alleles that will continue to exist. Gene flow takes place when genes are passed from a population to the other. Gene flow is also referred to as migration. The mutation is responsible for the genetic disparity in a gene pool.
With the improvements in the understanding of evolution and molecular biology, the definition of species in the past has been changed several times (Moore 67). In the past, the term species referred to organisms with identifiable traits that could be distinguished from other identical organisms. This definition was dropped because in a population, variation exists and not all members of a given species look alike. Currently, the biological species concept describes the species as creatures that can interbreed to bring into being fertile offspring.
Just like the other three forces, natural selection has been a means of evolution, whereas variation has been a requirement for the evolution process (Moore 87). Based on this fact, it can be argued that evolution can be realized in the absence of natural selection. However, evolution cannot be realized in the absence of variation. Variation is an important facet of the population. As such, variation is realized when organisms in a population varies in their distinctiveness.
Variation is attributed to mutation, immigration, and the mixing of genetic material. Through mutation, changes in the DNAs of reproductive cells are passed on to the next generations. Usually, genes mutate at the rate of one to ten times in one hundred thousand cell divisions.
This indicates that mutation is a rare and random process. Despite this, it should be noted that mutation is the leading cause of variation in a population. Mutation can be manipulated by environmental abuses such as radiation and uses of certain chemicals. Variation through gene flow is realized when an organism moves into a territory of another related organism but with different variations. When this occurs, the resulting population from both the native and the immigrants can be categorized as genetically varied.
Based on the above discussion, it is apparent that evolution is realized when inherited traits of a population or a species are altered over time. When these changes are realized, speciation can be said to have taken place. If reproductive isolation occurs over time between members of different demes, they may evolve into new species.
Mechanisms that inhibit breeding between populations, eventually leading to speciation are referred to as isolating mechanisms. These isolating mechanisms are categorized into prezygotic and postzygotic. Prezygotic mechanisms inhibit the formation of hybrids. On the other hand, postzygotic mechanisms inhibit hybrids from producing viable offspring. Geographical isolation is the major isolation mechanism in nature.
In conclusion, it should be noted that the concepts of evolution have changed and might continue to change in the future with the advancement in microbiology. Concerning population genetics, four basic forces influence evolution processes. These forces are natural selection, gene flow, mutation, and genetic drift.
Ayala, Francisco José, and Robert Arp. Contemporary debates in philosophy of biology. Chichester, U.K.: Wiley-Blackwell Pub., 2010. Print.
Moore, Randy. Evolution 101. Westport, Conn.: Greenwood Press, 2006. Print.