The Four Forces of Evolution
Organisms as we know them have undergone a process of evolution. This means that these complex plants and animals that we see today transcended from simpler and original states of the past. It is generally argued that evolution is a continuing process and that we are likely to have beings that are more complex in the future compared to those that presently dwell in this earth. The process of evolution is continuous and it occurs in plants and animals changing their traits, which are then transferred to subsequent generations. The present state of an organism is not its final state; this present state is considered a phase along its path of evolution (Darwin 2). The essay that follows will discuss the concepts of evolution with a bias on the four forces that fuel or drive evolution.
Four main forces are believed to drive evolution. As earlier stated, evolution is a continuous process which needs to be driven by some forces. The four forces of evolution drive it. However, before delving into the discussion of the forces, it is important to first distinguish two types of evolution i.e. microevolution and macroevolution. The former is defined as the small changes that occur in a gene pool of a population over some time. These changes are not big enough to lead to a formation of a new species (Darwin 3). Conversely, in macroevolution, changes that occur to an organism are significant and they often lead to an emergence of a new species. Additionally, it is important to note that the new organism that has emerged from macroevolution cannot mate with its ancestor reason being that the new species differs from its ancestor.
Interbreeding occurs in a population when the related species are within close proximity of each other. However, when speciation occurs, a new species emerges from the old species, in such case the ancestor, and the offspring species cannot interbreed because they seize to belong to the same species. Isolating mechanism might be at play in instances where the ancestor species looses the ability to interbreed with its offspring (Darwin 3). The variations that occur between species can be caused by any of the four forces of evolution.
Four Forces of Evolution
Evolutionary change is driven by the forces of mutation namely; migration, mutation, genetic drift, and natural selection. Mutation results after the sequence or order of one or more nucleotides on a species’ DNA is changed. Such an alteration of the DNA sequence can change the structure of protein coded or alter the process of protein regulation. Mutations can be either beneficial or harmful. Beneficial mutation gives rise to offspring that are superior to their ancestors while harmful mutation gives rise to offspring that are inferior to ancestors (Gillespie 2). The former might be well adapted to overcome the challenges that the parent species. On the other hand, the latter being inferior to the parent species might be weaker than the parent species.
The second force driving evolution is migration. In evolution, migration is taken to mean gene flow. Gene flow denotes the movement of alleles from one population or region to another. For gene flow to be recognized, the gene must be transferred from one population or region to another. The migrants that come into anew population become new contributors of their allele in the gene pool of that particular population (Andersson and Vicente 13). Supposing these migrants meet species that they can interbreed, they will give rise to new species in the population, and there are chances, that speciation might occur in the new population and the new species might not be able to interbreed with the species from whence they migrated. At such a point, we say that variation has occurred between the two populations.
The third force of evolution is genetic drift. Changes in allelic frequency within population are caused by genetic drift. This process does not bring in new alleles into the population, but has the ability of reducing variations in a population by removing alleles from the gene pool of an organization. Genetic drift is often caused by random sampling that occurs in sampling of alleles (Gillespie 7). Small populations are greatly affected by genetic drift. Genetic drift can be explained by founder effect and population bottleneck. Population bottleneck occurs when the population of a species is suddenly reduced drastically over a limited period because of external forces. On the other hand, founder effect occurs when a portion of a population splits off due to geographic isolation and forms a new population. This new population will have a different allelic frequency compared to that of the original population.
The fourth and final force of evolution is natural selection. Natural selection occurs where there is variation in traits, heredity, and differential reproduction. The variations in traits e.g. colour of the different species can cause some to survive better in the ecosystem that the other species (Darwin 4). Differential reproduction then steps in where not all species will reproduce to their expected full potential. Heredity will only occur in species that have survived the first two stages and a repeat of the processes is likely to eliminate the species whose members fail to reproduce offspring
In summary, evolutionary change is driven by the forces of natural selection, gene flow, genetic drift, and mutation. These changes lead to variation that might be have been caused by isolating mechanisms and variation, which leads to speciation within and between the populations. .
Andersson, Meike S, and M C. Vicente. Gene Flow between Crops and Their Wild Relatives. Baltimore: Johns Hopkins University Press, 2010. Print.
Darwin, Charles, and Charles Darwin. Natural Selection. London: Bibliolis Books, 2010. Print.
Gillespie, John H. Population Genetics: A Concise Guide. Baltimore, Md: Johns Hopkins University Press, 2004. Print.
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