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Evolution and Speciation’s Four Forces Essay


Evolution is a complex biological process that entails changes in innate characteristics of organisms over a short or a long period. The process of evolution is subject to many forces, which drive the development of species, variants, and populations of organisms. Thus, this essay seeks to define and examine micro-evolution and macro-evolution, species and population, evolutionary forces, variation, isolation mechanisms, and speciation as some of the important evolutionary concepts.

Micro-evolution and macro-evolution are two forms of evolution that occur among organisms. Essentially, micro-evolution is unique because it occurs over a short period, such as a generation and entails genetic changes of organisms. Micro-evolutionary changes are not visible because they happen at the genetic level and within current species (Bandey 74). Comparatively, macro-evolution is a form of evolution that occurs over a long period like geological time and entails the sum of all micro-evolutionary changes. The macro-evolutionary changes are very visible because they comprise morphological and physical changes.

Micro-evolution and macro-evolution usually occur within species and among populations of organisms. A species is a group of organisms that have the same genetic makeup in that they can interbreed and give rise to fertile young ones, which have the same genetic makeup as their parents. As a group of a certain species of organisms inhabits a given geographical area or an ecosystem, they constitute a population. Hence, the evolution of organisms occurs at the level of species and population.

The occurrence of micro-evolution and macro-evolution is subject to evolutionary forces, namely, mutation, gene flow, genetic drift, and selection. Genotypic and phenotypic variations that are common in organisms emanate from genetic changes that mutation cause. Replication errors, radiations, mutagenic chemicals, and micro-organisms are responsible for the mutations that arise during cell division. As gene flow drives the evolutionary changes, it is responsible for the marked changes that are evident among species and populations of organisms. According to Haviland, Prins, Walrath, and McBride, interbreeding makes genes to flow from one population to another, and thus, causes micro-evolution (42). The interbreeding within species and between populations is very important because it increases the diversity of genes in a gene pool.

In a certain gene pool, the diversity and the dominance of genes dictate the evolutionary process that organisms undergo. Genetic drift is a special evolutionary force that is dependent on the diversity of alleles in a given gene pool or population. Haviland et al. define genetic drift as “the chance fluctuation of allele frequencies in the gene pool of a population” (43). The definition indicates that the genetic drift is the tendency of the evolutionary process to follow certain alleles owing to their frequency in a population. Evolutionary forces like mutation, genetic drift, and gene flow trigger and perpetuate the evolution process and influence the survival of organisms. The selection forces determine whether organisms survive or become extinct. Haviland et al. state that the selection force increases the number of adaptive species and decreases the number of non-adaptive species in various populations, depending on the environmental conditions (44). Therefore, the selection force makes organisms to adapt their biological, social, and physical environments.

The evolutionary forces are responsible for the occurrence of variation within a population and between populations. Variation within a population owes its existence to micro-evolutionary forces such as mutation, genetic drift, gene flow, and selection, while variation between populations occurs due to isolation mechanisms of the evolutionary forces. The isolation mechanisms like geographical isolation, reproductive isolation, and genetic isolation prevent interbreeding, migration, and gene flow, and thus, cause speciation (Nosil 109). Specifically, speciation is the process through which new species of organisms emerge after a certain population undergoes isolation mechanisms.

In conclusion, the process of evolution is very complex because it is subject to forces such as mutation, gene flow, genetic drift, and selection. These forces operate within species and between populations and consequently lead to speciation. The speciation process depends on isolation mechanisms of the evolutionary forces.

Works Cited

Bandey, Gaya. Bicultural Evolution. New York: Concept Publishing Company, 2010. Print.

Haviland, William, Harald Prins, Dana Walrath, and Bunny McBride. The Essence of Anthropology. New York: Cengage Learning, 2012. Print.

Nosil, Patrik. Ecological Speciation. New York: Oxford University Press, 2012. Print.

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IvyPanda. (2020, May 12). Evolution and Speciation's Four Forces. Retrieved from https://ivypanda.com/essays/evolution-and-speciations-four-forces/

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"Evolution and Speciation's Four Forces." IvyPanda, 12 May 2020, ivypanda.com/essays/evolution-and-speciations-four-forces/.

1. IvyPanda. "Evolution and Speciation's Four Forces." May 12, 2020. https://ivypanda.com/essays/evolution-and-speciations-four-forces/.


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IvyPanda. "Evolution and Speciation's Four Forces." May 12, 2020. https://ivypanda.com/essays/evolution-and-speciations-four-forces/.

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IvyPanda. 2020. "Evolution and Speciation's Four Forces." May 12, 2020. https://ivypanda.com/essays/evolution-and-speciations-four-forces/.

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IvyPanda. (2020) 'Evolution and Speciation's Four Forces'. 12 May.

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