Are species plastic, frozen or elastic?

Only a negligible fraction of sexually reproducing species at a given time (the species originated recently, for example, by peripatric speciation) are plastic. Most species behave as elastic in microevolutionary processes and as frozen in macroevolutionary processes. They respond to a minor environmental change by reversible change (accompanied by a decrease in fitness) and to a major environmental change by extinction rather than by evolutionary adaptation. 

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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