Evolution can be defined as any cumulative change in populations or organisms’ characteristics over a period that involves generations – to put it in another way, ancestry with change. Evolution reflects organisms' adaptations to their varying surroundings and can result in new species, novel traits, and altered genes. The evolutionary progression depends on both modifications in allele frequencies and genetic variability. Human beings contribute to wild species evolution because of their various activities since they affect animals' environments. Evolution mainly involves alleles, defined as two or more forms of a gene. Human beings inherit two alleles, where every gene comes from each parent. Evolution is caused by four primary reasons; mutation, natural selection, gene flow, and genetic drift.
The mutation is crucial since it is the first stage of evolution. This is because it generates a new sequence of DNA for a particular gene in a precise locus within an organism, which leads to the creation of a new allele, and thus, mutation act as an evolutionary power within itself, to potentially cause significant alliterations in allele frequencies over time (Losos, 2017).). It might be a weak force of modifying allele frequencies but has the needed energy to introduce new alleles. Mutations arise naturally because of low frequencies due to pyrimidine and purine bases' chemical instability and any errors that might occur during DNA reproduction. An example of humans' evolution is hemoglobin's mutation that leads to red blood cells curving into a sickle-like shape.
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On the other hand, natural selection is also a driving force of evolution because it explains life's diversity on earth. It is the developmental progression where populaces of living organisms familiarize themselves with their surroundings and change. Since nature has a shortage of resources, organisms with heritable traits that favor reproduction and survival tend to reproduce more offspring than the organisms in their peer group (Delisle, 2021). Since the characteristics that helped the organisms survive and reproduce are heritable, they are passed from one generation to the other and become standard. As generations continue to increase, they become adapted to the environment. Natural selection makes populaces to be well-suited to their surroundings over time.
Nevertheless, genetic drift is an evolution mechanism where a population's allele frequencies change from one generation to another due to sampling error. Genetic drift might lead to loss of several alleles, including the most needed and beneficial ones, or a rise in allele frequency up to 100% (Losos, 2017).). It occurs and affects all populaces of non-infinite size, even though small populations are affected by its strength. Genetic drift might be more effective if a population is reduced in size. For example, a major disturbance like a natural disaster might radically decrease the population's size, and therefore, genetic variation is diminished. Such an effect is known as the bottleneck effect. If a group of a population separates from the central population to starts its colony, the consequence is known as the founder effect.
Another cause of evolution is flow, also referred to as gene migration. Gene flow can be defined as the transfer of any form of genetic material from one species’ populace to another, and therefore changing the gene’s composition of the receiving populace (Losos, 2017).). The process can occur between two populaces of a similar species. The process occurs because of migration when alleles are transferred in and out of gene pools. For instance, gene flow is experienced in most species of baboons. In most cases, female baboons mate in troops with dominant male baboons. Young male baboons leave the troops where they were born almost every time, mainly to avoid inbreeding. They join new troops, where they might mate with other females to have their offspring inherit their genes. Typically, evolution is trait changes of different species from one generation to another over time. It is based on the concept of a species and is the involvement of genes.
References
Delisle, R. G. (2021). Natural selection as a mere auxiliary hypothesis (Sensu Stricto I. Lakatos) in Charles Darwin's origin species. Natural selection: revisiting its explanatory role in evolutionary biology. Springer, Cham, 73-104.
Losos, J. B. (2017). The Princeton guide to evolution. Princeton University Press.
