Four Forces of Evolution

Evolution is the series of changes by which plants and animals are transformed from their simplest and original states to their present states which are more sophisticated or complex. These changes are continuous and they take place over many generations. Evolutionary changes in plants and animals are genetic properties, characteristics or traits that are being passed down from one generation to the other. The present state of an organism is only a phase in this never-ending process of change. There are four major natural phenomena that are believed to be the driving forces behind evolution. These forces are: Mutation, Gene Flow, Genetic Drift, and Natural Selection.

Mutation is the sudden and permanent change in the properties of an organism’s gene that results in new traits which can be passed on to the next generation. Gene is contained in the hereditary material of life called DNA. DNA determines the shape, size, behaviour and as a matter of fact, the entire life of the organism. A change in the DNA brings about a resultant change in the properties of the gene which in turn leads to tremendous changes in all aspects of the organism’s life. Mutation is seen as one of the forces of evolution because the mutated gene is transmitted to the organism’s offspring and therefore the next generation. However, not all mutations result in evolution. Some mutations occur in the non-reproductive cells of the organisms and as such, are not transmitted to the offspring. These mutations are called somatic mutations. Germ line mutations occur in the reproductive cells and can be transmitted to the offspring.  These are only the type of mutations that result in evolution.

Gene Flow, also known as gene migration, is the transfer of gene from one population to another thereby changing the genetic composition of the new population.  Gene flow generally caused by immigration and dispersal, happens when people move to a new population or pollen is being blown to a new destination. If these newcomers carry different genes to their new environment and mate with the members of the population, genetic variation results, and this plays a major role in evolution. Hence, gene flow is seen as one of the mechanisms of evolution.

Genetic Drift is the change in frequency or number of a gene in a population. This change also called allelic drift, happens over time by chance events or random processes. Genetic drift affects the genetic composition of the population and that of the next generation thereby bringing evolution into play once again.

Natural Selection, an important mechanism of evolution, is the process by which some genetic traits become either more or less dominant in a population. Natural selection only affects the phenotype or physical traits but these traits are determined by the genotype. As time goes by, some physical traits in the population become more dominant while some other traits disappear and don’t get passed on to the next generations.

These four forces have played major roles in the evolution of all plants and animals over many generations and for many years to come will continue to determine how subsequent generations evolve from their ancestors.
Variety is the spice of life.