BIOL 1001 Chapter Notes - Chapter 20: Evolutionary Developmental Biology, Punctuated Equilibrium, Exaptation
21 Feb 2012
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Document Summary
The earliest horses were small and stood at 25-50 cm high, walked on soft pads like dogs, faces were short, and ate leaves in woodland habitats. The evolution of these horses caused them to run faster and change diet to tough grasses and live in open grasslands. The evolution of horses had many branches and lineages, but today only genus survives with many species (including donkeys and zebras). Anagenesis- the accumulation of changes in a lineage as it adapts to changing environments. It does not increase the number of species, only transforms an existing species. Cladogenesis- the evolution of two or more descendant species from a common ancestor. The gradualist hypothesis- suggests that large changes result from slow, continuous accumulations of small changes over time. Gradual fossil records are most often not found. Usually you find fossils of one species and then it disappears and find fossil of the next in next stratum.
