BIOL 123 Lecture Notes - Lecture 27: Phosphatidylcholine, Monophyly, Sex Steroid
Document Summary
A three-domain system more accurately reflects life"s history. Carl woese discovered that prokaryotes actually include two very different kinds of organisms - bacteria and the archaea. Early in history the tree of life split into three domains: bacteria, archaea, and. When two or more taxa share a derived trait, the shared trait is said to be a synapomorphy. Monophyletic groups contain all of the living descendants of a common ancestor. Paraphyletic groups contain some, but not all, of the descendants of a common ancestor. Species designations change when new information is discovered. The biological species definition can be difficult or impossible to apply. It is difficult to apply a biological species definition to asexual organisms like most bacteria, archaea, and protists because the criterion of interbreeding cannot be used to distinguish among species. Biodiversity = total range of species diversity. Of all species identified thus far, 5% are prokaryotes and protists.
