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Published byVictoria Cain Modified over 9 years ago
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Macroevolution
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Gradualism & saltation Gradualism: large changes in phenotypic characters have evolved through many slightly different intermediate states Saltation: a discontinuous mutational change in 1+ phenotypic traits, usually of considerable magnitude
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gradualism saltation
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Gradualism & saltation Gaps in the fossil record 1Gaps are real 2Gaps reflect inadequate fossil record
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Gradualism intermediates functional considerations fitness effects of mutation genetic differences
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Saltation radiation & stasis Goldschmidt - hopeful monster Eldredge & Gould - punctuated equilibrium
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Adaptive radiation: single or small group of ancestral species rapidly diversify into a large number of descendent species that occupy a wide variety of ecological niches Adaptive radiation
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Hawaiian honeycreepers Adaptive radiation
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Living fossils horseshoe crab
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Zigzag evolution Zigzag evolution: changes fluctuate around a mean value
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Niles EldredgeStephen J Gould Punctuated equilibrium Punctuated equilibrium - rapid evolutionary change followed by long periods of stasis
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gradualism punctuated equlibrium Rates of evolutionary change
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bryozoans Stasis
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evolution by jerks populations can evolve without speciating stable lineages are not absolutely static most fossil sequences incomplete during which characters can evolve substantially selection within species is quicker than speciation and extinction Punctuated equilibrium criticisms
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