Variability is the ability to produce variants.In order for a system to be able of becoming a subject of natural selection, it must contain elements that are capable of changing over time, of producing variants differing in smaller or larger details. Variability can again be realized in various ways. In modern organisms, mutations occur as the main source of variability, i.e. errors usually occurring during the replication or repair of DNA.

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The classical Darwinian theory of evolution can explain the evolution of adaptive traits only in asexual organisms. The frozen plasticity theory is much more general: It can also explain the origin and evolution of adaptive traits in both asexual and sexual organisms Read more