The Four Forces of Evolution and Variation
The four forces of evolution are mutation, genetic drift, gene flow and natural selection. Mutation refers to changes in the De-ox ribonucleic (DNA) sequence of a particular cell’s genome. If a mutation occurs, it can alter the gene product, prevent a gene from functioning, or have no effect (Carroll, 2005). This may result to variation in a population. Examples of variations brought about by mutations are hereditary conditions like sickle-cell anemia and Down’s syndrome.
According to Jablonka and Raz (2009), genetic drift refers to random changes in gene frequencies of a population. It is sometimes referred to as an allelic drift as it involves a change in an allele’s frequency in a given population because of random sampling. Genetic drift may make an allele to disappear and, as a result, reduce genetic variation. Alleles in an offspring represent a sample of the parent’s alleles. Chance determines whether the individual survives or reproduces. This force greatly influences variation in small populations.
Gene flow refers to how genes move from one population or species to another. It is also referred to as migration. Its presence or absence greatly changes an evolution’s course. Gene flow may introduce traits or gene variants that are disadvantageous in a given population. This may make organisms in the population to evolve mechanisms to prevent mating with populations that are genetically distant. This then leads to the formation of new species. Gene flow impacts variation within a population as well as between populations.
Natural selection posits that genetic mutations which enhance reproduction remain common in successive population generations (Cutter & Choi, 2010). Survival for the fittest ensures that only individuals that can survive and reproduce remain, and thus determine the amount of genetic contribution in the subsequent generation. This suggests that weak members of a population are naturally replaced by members with strong genetic composition. Natural selection can act on genes, individual organisms, populations and species to bring about variation.
An isolating mechanism is a feature involving behavior, morphology or genetics that serves to stop breeding between species. On the other hand, speciation refers to how a species may diverge into two or more species (Dawkins, 2006). The four forces of evolution discussed above are crucial in explaining how isolating mechanisms lead to speciation. For instance, changes to DNA sequences due to mutations may prevent a gene from functioning (this is the isolating mechanism). This then makes the force of natural selection to determine what the future generation of a species would be (this is speciation).
In conclusion, the four forces of evolution are responsible for creating isolating mechanisms that lead to speciation.