Biology 1001A Lecture Notes - Lecture 18: Anagenesis, Cladogenesis, Gradualism
18 Oct 2012
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Only synapomorphies are informative: not all similarities are homologies, not all homologies are synapomorphies. Homoplasy is misleading: creates similarity between distantly related groups, erases similarity between closely related groups. Most parsimonious tree (fewest evolutionary steps) is usually the best. Many currently-recognized groups" are not monophyletic not good" groupings: monophyletic group: includes all descendants of the group"s most recent common ancestor, blue is better below. Purple circle is good tree, least number of evolutionary steps. Reptiles are not monophyletic: lizards and crocodiles are most related with birds. Prokaryotes are not true monophyletic: related with bacteria and archea. Recent formations are more likely to be found, than older ones. Ancient rocks have been eroded, therefore, likely to find newer ones: taxonomic. Hard shells, bones, sturdy structures are most likely to be fossilized compared to worms, flowers and etc : habitat. New species can appear; via anagenesis or cladogenesis. Anagenesis: species formation without branching of the evolutionary line of descent.
