Evolution refers to the biological changes that occur among individual members of population over time. The changes are usually due to biological conditions and environmental factors. However, it is important to note that the entire population undergoes evolution and not just the individuals in such a population. There are four known forces of evolution and they include natural selection, gene flow, genetic drift, and mutations.
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Natural selection involves differential survival traits. Different individuals in a given population will adapt to different characteristics. Consequently, they are able to compete with other species for scarce resources. Due to intense competition, species that are able to adapt to these characteristics survive while the rest become extinct. Many scientists refer to this phenomenon as survival for the fittest.
This is a situation in which individuals who lack the ability to adapt to the needed characteristics are wiped out. At the same time, the traits of a given generation can change from one generation to another. Natural selection affects variations in a population through changes that occur to the phenotypes of different organisms. What this appears to suggest is that natural selection calls for behavioral and structural changes of body parts.
On the other hand, gene flow is a term used in reference to the movement or migration of genetic materials across different populations. The flow of genes within a population increases variations of individuals within that population. Gene flow occurs mainly due to the highly mobile organisms in a population.
Mobile organisms are able to interact with other organism and as a result, the exchange of genetic material from one organism to another takes place. This is what usually happens during mating. The resulting generations will thus posses the dominant genes from the two parents. In most cases, the resulting generations possess the hybrid genes of the parent genes.
In genetic drift, some individuals may leave behind a higher percentage of genes than others. Consequently, some genes may end up drifting away as new generations are produced. The genes that drift away are usually lost forever. That is why certain organisms become extinct.
Thus, genetic drift reduces the chances of genetic variations from one generation to another. Mutation is the change that occurs to the DNA material of organisms. Mutations can be harmful or beneficial. Mutations that contribute a lot to evolution are those that occur in the sex cells, as opposed to the somatic cells. This is because it is only the changes that occur in the reproductive cells that can be passed from the parent to an offspring.
Mutations can lead to changes in the phenotype of organisms. A single mutation can bring about unnoticeable or small change in an organism. It can also result in a big change in another type of organism. Sometimes, mutations do not cause any changes to organisms. Thus, mutations produce noticeable changes only when the genes involved are similar.
An isolation mechanism is any factor that prevents groups of organisms from interbreeding. Isolating mechanisms can be behavioral or biological. For example, different seasons of mating for different organisms may hinder two different groups of organisms from interbreeding. Again, sterile organisms from a certain group are not able to interbreed. Consequently, similar organisms end up interbreeding. This enhances speciation, in which similar off springs are produced.