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Definition

noun, plural: evolutions

(1) The change in genetic composition of a population over successive generations, which may be caused by natural selection, inbreeding, hybridization, or mutation.

(2) The sequence of events depicting the development of a species or of a group of related organisms; phylogeny.

Supplement

Evolution pertains to the sequence of events depicting the gradual progression of changes in the genetic composition of a biological population over successive generations. Accordingly, all life on earth originates from a common ancestor, which is referred to as the last universal common ancestor, some 3.5 to 3.8 billion years ago.

In order for evolution to occur, there must be genetic variation. Genetic variation brings about evolution. Without it there will be no evolution. There are two major mechanisms that drive evolution. First is natural selection. Individuals with advantageous traits are more likely to reproduce successfully, passing these traits to the next generation. This kind of evolution driven by natural selection is called adaptive evolution. Another mechanism involves genetic drift, which produces random changes in the frequency of traits in a population. Evolution that arises from genetic drift is called neutral evolution.

Word origin: Latin evolutio (an unrolling, unfolding), ex- (from, out of) + volere (to roll)

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Evolution - Biology-Online Dictionary