Natural Selection Impacts Evolution: Limitations & Consequences - Essay Sample

Introduction

Natural selection is a significant concept in evolution and can be used to generate populations that are suited to survive, and successfully reproduce in their context (Lumen Boundless Biology n.p). However, natural selection cannot produce perfect species, since this concept can only choose on existing variation in the population, and cannot produce any species from scratch. (Lumen Boundless Biology n.p). Hence, the evolution process can be said to be restricted by a population's existing genetic variance, the physical closeness of species, non-beneficial intermediate morphs in a polymorphic population, and non-adaptive evolutionary forces (Lumen Boundless Biology n.p). Therefore, the paper will discuss why no perfect species is using key topics like adaptive evolutionary forces, mutations, and extinctions.

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Limits to Natural Selection

Natural selection emerges from genetic variation in the ability to reproduce. The organized accumulation of chance variations is the only way that can contribute to biological adaptations, and the outcome has been positive (Barton, Nick, Partridge 1075). Although it does not produce perfect species, several organisms produced through natural selection can live in harsh environments and on diverse energy sources. The aspect of mutation can also be used to explain why there are no perfect species. For example, In a densely populated area, a balance is arrived at between selection and toxic mutations that reduce mean fitness (Barton et al. 1077-1078). This restricts the net mutation rate, and therefore, the size of the functional genome that can be generated by selection (Barton et al. 1079). From the perspective of asexual reproduction, a simple argument shows that harmful mutations decreases mean fitness by a great mile (Barton et al. 1079). Therefore, only fittest organisms can be able to thrive in the population.

On Polymorphism, natural selection can be limited by the association between different polymorphisms. One morph may generate higher adaptability or fitness than the other, however, it may not augment in frequency since the intermediate morph is damaging (Lumen Boundless Biology n.p). For instance, in a supposed population of mice, some were noticed to be light-colored, and blended well with the sand, while others were dark, and blended properly with the patches of black rock (Lumen Boundless Biology n.p). The dark-colored mice may be argued to be fitter than the light-colored mice, and as per the concept of natural selection, the numbers of light-colored mice are anticipated to plummet over some time (Lumen Boundless Biology n.p). This notion is known as the disruptive selection, and can also explain why there are no perfect species, as seen in the above example.

The three types of natural selection include; directional, stabilizing, and disruptive. From the perspective of directional selection, the adaptability of a species augments with genetic value (Carey 4). Adaptability is lower for lower species of the phenotype and gradually becomes progressively larger for huge phenotypic values (Carey 4). Under the second mode, stabilizing selection, the genetic values that are close to average have higher adaptability, and their adaptability to an environment will decrease as an organism shift away from the mean (Carey 4). In most cases, biologists equate natural selection to directional selection mode. In a nutshell, most organisms are well suited to their environment but are not born perfectly suited to their ecological niches as explained in the two modes of natural selection. The final model of natural selection is known as disruptive selection. In this case, organisms close to average have decreased adaptability levels compared to those at the extreme levels. Although, this form of selection appears to be the rarest model of natural selection (Carey 5-6).

The genetic parameter is described as the change in gene frequencies over some time due to chance, and chance alone (Carey 6). To explain genetic drift, imagine the change over time in allele A in a small restricted population of ten organisms. Supposing that the occurrence of A is .50, and the frequency of the other allele, a, is equally .50 (Carey 6). The results are expected to be as follows; in 10 organisms, there will be 20 alleles (10 A alleles, and 10 a, alleles). In shifting these genes to the next generation, the propensity of transmitting A is the same chance as tossing a fair coin 20 times to get 10 head and 10 tails (Carey 6). From this example, it can be concluded that there are no perfect species, as probably changes in gene frequencies of one generation can change the chance of transmitting the allele to the next generation that may be best suited to it (Carey 7-9).

The impact of a mutation relies on where the mutation happens in the genome. If the mutation happens in a DNA selection that does not have a code for peptide chain, does not control the production of a peptide chain, there may be no impact of the ensuing replication of DNA molecule (Carey 9-10). Neutral mutations are those that do not affect the eventual reproductive adaptiveness of an organism and give rise to neutral genes (Carey 9-10). On the other hand, the most likely impact of mutation that affects an organism is to reduce the adaptability.

The five forces of evolution do not function in five distinct vacuums with each energy doing its thing self-reliantly of the other four (Carey 18-19). The five forces rather have active interactions, making it very hard for humans to intellectualize the evolutionary process. Wright's synthesis of the shifting balance concept was presented in not less than four aspects, but he also provided a simple rationale for understanding it (Carey 18-19). When a species becomes well adapted to its ecological niche, the allele stays in a pit (Carey 18-19). As the environment for these organisms changes, the landscape itself changes (Carey 19-20).

Conclusion

In conclusion, the essay has explained why there are no perfect species, and that an organism gradually acquires traits that make them suitable for an ecological niche after going through various modes of natural selection, and mutation. In stabilizing selection, the genetic values that are close to average have greater adaptability, and their adaptability to an environment will decrease as an organism shift away from the mean. In disruptive selection, the organisms close to average have decreased adaptability levels compared to those at the extreme levels. Finally, in the directional selection, adaptability is lower for small species of the phenotype and gradually becomes progressively larger for huge phenotypic values.

Works Cited

Barton, Nick, and Linda Partridge. "Limits to natural selection." BioEssays 22.12 (2000): 1075-1084. Retrieved from http://www.ufscar.br/~evolucao/popgen/ref12-5.pdf

Lumen Boundless Biology." Adaptive evolution: natural selection and adaptive evolution." Retrieved from https://courses.lumenlearning.com/boundless-biology/chapter/adaptive-evolution/

Carey, Gregory. " The five forces behind human evolution." 1-29. Retrieved from http://psych.colorado.edu/~carey/hgss/hgsschapters/HGSS_Chapter13.pdf