Punctuated Equilibrium is an evolutionary theory first suggested by Stephen Jay Gould and Niles Eldridge (www.pbs.org). The theory states that evolution takes place in a short amount of time in a species history. These changes take place in rapid bursts (www.evolution.berkely.edu). The theory takes place in 7 steps from stasis to rapid bursts to reintroduction.
In contrast, evolutionary biologists like Jay Gould have also discussed the theory of "phyletic gradualism" which attributes speciation to a "slow and steady transformation of entire populations" (Eldredge and Gould, 1972). Much debate surrounds the topic of punctuated equilibrium as a mode of speciation, rather than just being a result of gaps that exist in the fossil record.
Examples[]
An example of punctuated equilibrium is the fossil mollusks of East Africa (Hicke, J.)
References[]
Hicke, J. www.webpages.uidaho.edu/~jhicke/.../chapter_09.1_evolution.pdf
www.pbs.org/wgbh/evolution/library/03/5/l_035_01.h
http://evolution.berkeley.edu/evosite/evo101/VIIA1bPunctuated.shtmltml
Eldredge, N. and Gould, S.J. (1972). Punctuated equilibria: an alternative to phyletic gradualism. In Schopf, Thomas J.M. (ed.). Models in Paleobiology. San Francisco: Freeman, Cooper and Company, pp. 82-115.