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However, the punctuational equilibrium model may still be inferred from both the observation of stasis and examples of rapid and episodic speciation events documented in the fossil record. [70] Dawkins also emphasizes that punctuated equilibrium has been "oversold by some journalists", [71] but partly due to Eldredge and Gould's "later writings ...
Different modes of speciation include sympatric and allopatric). Additionally, scientists research the 'tempo' of speciation, i.e. the rate at which species change genetically and/or morphologically. Classically, competing hypothesis for the tempo of specieation include phyletic gradualism and punctuated equilibrium). Lastly, what are the ...
Gould's most significant contribution to evolutionary biology was the theory of punctuated equilibrium [2] developed with Niles Eldredge in 1972. [3] The theory proposes that most evolution is characterized by long periods of evolutionary stability, infrequently punctuated by swift periods of branching speciation.
In evolutionary biology, punctuated equilibrium (also called punctuated equilibria) is a theory that proposes that once a species appears in the fossil record, the population will become stable, showing little evolutionary change for most of its geological history.
Gould's initial work on punctuated equilibrium was coauthored with Niles Eldredge. [20] Gould's model of punctuated equilibrium drew attention to episodic bursts of evolutionary change followed by periods of morphological stability. He challenged the conventional model of gradual, continuous change - called phyletic gradualism. [21]
In the 1980s, the American palaeontologists Stephen Jay Gould and Niles Eldredge argued for an extended synthesis based on their idea of punctuated equilibrium, the role of species selection shaping large scale evolutionary patterns and natural selection working on multiple levels extending from genes to species. [30] [31] [32] [33]
Punctuated gradualism is considered to be a variation of these models, lying somewhere in between the phyletic gradualism model and the punctuated equilibrium model. It states that speciation is not needed for a lineage to rapidly evolve from one equilibrium to another but may show rapid transitions between long-stable states.
The punctuated equilibrium model of policy change was first presented by Frank Baumgartner and Bryan Jones in 1993, [1] and has increasingly received attention in historical institutionalism. [3] The model states that policy generally changes only incrementally due to several restraints, namely the "stickiness" of institutional cultures, vested ...