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Punctuated Equilibrium & Gradualism

Punctuated Equilibrium & Gradualism. Punctuated equilibrium describes the pattern of long stable periods in which species stay the same. These periods are interrupted (or punctuated) by short periods in which the quick pace of evolution rapidly results in the formation of new species.

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Punctuated Equilibrium & Gradualism

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  1. Punctuated Equilibrium & Gradualism

  2. Punctuated equilibrium describes the pattern of long stable periods in which species stay the same. • These periods are interrupted (or punctuated) by short periods in which the quick pace of evolution rapidly results in the formation of new species. • The stimulus for evolution is a sudden, significant change in the environment.

  3. Gradualism describes the pattern of slow and gradual evolutionary change over long periods of time. • Populations slowly diverge from one another due to differing selective pressures.

  4. Neo-Darwinianism • As Darwin’s theories came to be contradicted even by evolutionists, evolutionary theory has changed and adapted to encompass new ideas including findings from genetics, population biology, and paleontology. • Theodosius Dobzhansky (1900-75) famously stated, “Nothing in biology makes sense except in light of evolution” (1973). • Stephen Jay Gould (1941-2002) came up with the hypothesis of punctuated equilibrium.

  5. Response to Creationist Criticism • Proponents of punctuated equilibrium argue that transitional forms between species are missing because evolution occurs so rapidly in a very short period of time. • Gradualists believe that transitional forms of organisms or missing links between species are missing from the fossil record because they are rare. • Between the two points of view, evolutionists have constructed a nice bit of circular logic.

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