What is Evolution?
(Updated: February 17, 2004)
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"Evolution" in it's simplest definition means change. However, "change" is too general a term to adequately describe the evolution of biological entities. Individuals can change, but they do not evolve. Populations (i.e. a group of some species) on the other hand, can genetically change over time and may evolve into different species. How, exactly, might populations evolve? How do new species form from old ones? There are several mechanisms that can be involved in the evolution of a population or of a species. The Darwinian paradigm holds that natural selection acts gradually on individual variation in populations over long periods of time. "Selection" is not the only driving force in evolution. Mutation is important, since mutation gives rise to the genetic variation on which natural selection acts. In some cases, genetic drift (e.g. founders effects) may be more important than selection. Migration (e.g. gene flow) between populations can introduce new variation. Endosymbiosis (e.g. the engulfment of a bacterial parasite by a host resulting in a union) is also an important evolutionary force and raises the question: what is an individual? The following sections contain information on some aspects in evolutionary theory.
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