Microevolution refers to the change that occurs in allele frequencies as a result of natural selection, gene flow, genetic drift and mutation. Macroevolution on the other hand refers to trends, big-scale patterns and change rates in families and other more overall species’ groups. A species refers to a group of organisms that are able to interbreed giving rise to viable offspring. A population refers to organisms of the same species that have interbred and live at the same geographical location at the same time.
There are four forces that influence micro to macro evolution. These include; mutation, selection, genetic drift and gene flow.
Mutations are DNA cell sequence changes each cell’s genome that are brought about by radiation, transposons, viruses, mutagenic chemicals and errors that occur whilst cells undergo meiosis which is the basis of DNA replication. Mutations alter the phenotype of an organism especially if they take place within the gene’s protein coding sequence. Mutagenic chemicals necessitate errors in DNA replication. For organisms that use chromosomal crossover for DNA exchange and gene recombination, meiosis alignment errors can cause mutations. Mutations can alter the genetic product or deter the gene from functioning.
Selection refers to the process whereby traits that favor an organism’s survival become more produced over successive generations. Sometimes artificial selection takes place but natural selection always dominates. Natural genetic variation gives an implication that some organisms will thrive well in the current environment unlike others. Natural selection has its effect on the phenotype but the genotypic characteristic that gives the reproductive advantage will eventually be common in the given population. Over time, adaptations in accordance to various ecological niches eventually develop leading to new species’ emergence.
Genetic drift refers to relative frequency change in an allele in a population as a result of random sampling. Chance plays a role that determines a specific individual will survive and reproduce. Genetic drift leads to variations in allele frequencies as time goes by. It may result in some traits making a total disappearance hence reducing their genetic variability. Genetic drift effect is felt more in small populations.
Gene flow refers to genes’ exchange between populations that belong to a similar species. An example is migration and interbreeding of organisms and pollen exchange. Population emigration or immigration can alter allele frequencies hence introduce genetic variation into the population.
Variation refers to individual characteristics’ difference from other members of the same species in a population.
An isolating mechanism is a factor that deters breeding between members of two different species from taking place once they copulate. These factors may also ensure that he offspring resulting from their mating is sterile. They maintain integrity among species and ensure that their traits are conserved. There are those that act before mating and there are those that act after mating.
Speciation is an evolutionary process that gives rise to new biological species. Speciation exists in four modes i.e. allopatric, peripatric, sympatric and parapatric. Speciation is therefore responsible for the splitting of lineages.
Works Cited
Cook O. F. (1906). "Factors of species-formation". Science 23 (587): 506–507.
J.M. Baker (2005). "Adaptive speciation: The role of natural selection in mechanisms of geographic and non-geographic speciation". Studies in History and Philosophy of Biological and Biomedical Sciences 36 (2): 303–326.
