Natural Selection
Various scientists consider natural selection as one of the various processes by which evolution occur within a specific population of organisms. Moreover, it is considered as a vital aspect of the modern biology. Natural selection explains the natural genetic variation within population of organisms. It works in any phenotypic traits and selective pressure is triggered by any aspect of the environment including competition among members of similar species and sexual selection. This relates natural selection to general biology which involves the study of living organisms their, taxonomy, distribution, origin, growth evolution, structure function and life.
Heritable genetic variation that causes fitness differences is required for natural selection to give adaptive revolution, speciation and novel traits. In fact, genetic mutation occurs as a result of alteration, recombination and mutation in the karyotype. Changes in the size, shape, number and the internal alignment of chromosomes causes either a disadvantage or an advantage though large effects are minimal. The effects of mutation in terms of average fitness and mutation rate depend on organism. Individuals with greater fitness stands a better chance of generating the off-springs in the next generation as the less fit individuals fail to reproduce or die before the reproduction age. This increases the alleles which in turn increase the fitness and they dominate against the alleles which reduce fitness in the next generation. If this selection pressure is maintained in several generations, beneficial allele increases continually increasing their abundance until they dominate the entire population as the less fit alleles continually decrease and finally disappear from the population. However, in every generation new recombinants and mutations develop creationg new phenotype spectrum. Natural selection eliminates the organisms that are less adapted hence eliminating the mutation that contributes to less fit and genetic variation. However new mutation occur leading to mutation selection balance. Changes in selection pressure leads to different mutation-selection balance. It therefore means that the increasing abundance of the alleles that causes the selection-favored traits enriches each new generation along successive generations.
The functions of most genes are regulated by regulatory genes regulate. When mutation occurs in the regulatory genes, they cause great effects on the individuals phenotype. Most of the mutation in the regulatory genes causes non-viable zygote. For example mutation in HOX human genes results to cervical rib or increase in the total number of toes or fingers. In cases where such mutations lead to higher fitness the phenotypes are favored by the natural selection thus the cervical rib or the increased number of toes or fingers dominates in the population.
The fitness of a trait is determined by the environment. This means that trait can be fit in a certain environmental context and in change of environmental condition the trait becomes less fit. Natural selection preserves such traits which in its absence can vary, deteriorate or even result to vestigial manifestation which in turn retains limited functioning or is used at an advantage of other traits.
The unit of selection is usually individual or a level of biological organization hierarchy such as kin group, cell or genes. Occurrence of selection at different levels increases the fitness of the level while reducing the fitness of the organism possessing the level through intragenomic conflict. However, the combined effects of selection pressure at various levels influences the overall fitness of an organism hence natural selection.
Organisms maintain natural selection throughout their life stages. Viability selection is the selection of individual organisms that survive until adulthood a stage at which they are ready to reproduce. In most species mature adults compete for mating partners through sexual selection and their success predicts the parents of the next generations. Organisms that get the chance to reproduce many times increase their length of survival in the productive phase and subsequent survival selection.
Populations of interbreeding organisms can change considerably given time and space. Based on evolution this means that the traits of populations living today are different from the traits in population that lived in the recent past. Moreover, the populations occupying a specific geographical region differ either in behavior or form. Although organisms share common ancestors, over time the populations divide to form different species, but they maintain the common ancestor.
Natural selection in evolution means species adapting to their environment and subsequent evolutionary change as the individuals with a specific character trait have greater reproductive and survival rate compared to individuals of the same population who do not have the trait. Genes of the species pool and adapt to survive longer through their off-springs. The natural selection concept predates peoples understanding on genetics. It is understood that selection works on the phenotype of organisms or their identifiable traits but organisms genotype is all what is inherited. In this line of understanding an organisms phenotype is the result of its genotype and the environment in which it lives. This describes the link between genetics and natural selection. Many scientists holds an understanding that natural selection is fundamental evolution mechanism, though the evolution theory holds an account of sexual reproduction and mutation and gene flow as the major sources of genetic variation. In this understanding, Charles Darwin used the Galapagos finches as examples to describe natural selection. The Galapagos finches are capable of feeding in various ecological niches due following adaptation. Over time, their beaks that were thin and slender for effective poking into the ground to extract grubs have evolved to suit their functions in various ecological niches. In Galapagos Island, there is a mixture of finches that dwell on the ground and on trees but the multiple species coexist as a result of diversification. Adaptive radiation modified their original colony that lived in South America and following the competition for the resources, they moved to the Galapagos Island where they continually adapted to benefit from the resources that were available. Since the finches with parrot-like beaks are favored over the ones with thin and slender beaks in struggle for food the trait is passed from one generation to another as they continue to reproduce within population thus changing the traits frequency. As the finches continue to compete for food, they adapt inhabitants of the ecological region with regard to the perfection of their associate.
Politicians view
Political entities such as Herbert Spencer denied the Darwin arguments on natural selection arguing that evolution involved inheritance of acquired characteristics hence the physiological changes over organisms life as purportedly get transmitted to organisms of spring.
Personal opinion
Natural selection is fundamental evolution mechanism, though the mechanisms such as mutation, sexual reproduction, and gene flow contribute to genetic variation. Furthermore, natural selection is not always directional and does not necessarily lead to adaptive evolution as it maintains the status quo through elimination of the organisms that are less fit.
Conclusion
Natural selection explains the natural genetic variation within population of organisms. It works in any phenotypic traits and selective pressure is triggered by any aspect of the environment including competition among members of similar species and sexual selection. This relates natural selection to general biology which involves the study of living organisms their, taxonomy, distribution, origin, growth evolution, structure function and life. In evolution natural selection means species adapting to their environment and subsequent evolutionary change as the individuals with a specific character trait have greater reproductive and survival rate compared to individuals of the same population who do not have the trait. Moreover, genes of the species pool and adapt to survive longer through their off-springs
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