Evolution
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This article provides an overview of the Evolution of populations and the mechanisms that derive it.
What is Evolution?
The theory of evolution explains how populations of organisms have changed over time. Evolution does not refer to changes that occur in an individual within its lifetime but it refers to changes in the characteristics of populations over the generations. These changes, which include modifications in structure, physiology, ecology and behaviour, may be so small that it is difficult to detect them or such great that the population differs from its ancestral population noticeably. Eventually, two populations may diverge to such a degree that we refer to them as different species.
Evolution has two main perspectives: microevolution and macroevolution. The evolution of populations is best understood in terms of phenotype, genotype and allele frequencies.
Evolution - Deriving Mechanisms
Two major mechanisms drive evolution; the first is natural selection and the second is genetic drift. Other mechanisms evolving in the evolutionary process are:
Each population possesses a gene pool including all the alleles for all the genes present in it. Allele and/or genotype frequencies may be changed by the evolution deriving mechanisms.
Natural Selection=
Charles Darwin, in his 1859 seminal book, “On the Origin of Species”, named the differential survival and reproductive success of individuals as natural selection. By natural selection, individuals of a population that enjoy more successful adaptations to the environment have more chances to survive and reproduce. Natural selection fights back seriously abnormal phenotypes as well as eliminates harmful mutations or reduces them. Over successive generations, the proportion of favourable alleles cause the population to increase. In contrast with other microevolutionary processes such as non-random mating, mutation, genetic drift and gene flow, natural selection leads adaptive evolutionary change.
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