Macroevolution

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

gradualism saltation

Gradualism & saltation Gaps in the fossil record 1Gaps are real 2Gaps reflect inadequate fossil record

Gradualism intermediates functional considerations fitness effects of mutation genetic differences

Saltation radiation & stasis Goldschmidt - hopeful monster Eldredge & Gould - punctuated equilibrium

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

Hawaiian honeycreepers Adaptive radiation

Living fossils horseshoe crab

Zigzag evolution Zigzag evolution: changes fluctuate around a mean value

Niles EldredgeStephen J Gould Punctuated equilibrium Punctuated equilibrium - rapid evolutionary change followed by long periods of stasis

gradualism punctuated equlibrium Rates of evolutionary change

bryozoans Stasis

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