Biology 1001A Lecture Notes - Lecture 4: Agnatha, Global Catastrophic Risk, Protostome
4 Dec 2013
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Document Summary
Most recent common ancestor (mrca) for a given group(s), given a phylogenetic tree. Why the idea that humans are descended from chimps is inaccurate. Which branched off into humans and chimps along two separate evolutionary lines. Order of main branching events in tree of life (dates not testable). see slide show. Cause of global catastrophe associated with mass extinction 65 mya. Relative species richness of protostome vs. deuterostome animals. There are many more protostome compared to deuterostome. Why some traditional groupings of organisms ( reptiles , fish ) do not reflect evolutionary relationships. Some reptiles share more recent common ancestor with birds than other ancestors. Reptiles is not a sensible group unless we include birds into group. Only eukaroyta are multi-cellular (plants, animals, fungi, etc) Some species differ from others in very minor ways, so, difficult to determine. This is because a species is defined as a distinct group of organisms that can reproduce and produce fertile offspring .
