Biology 2001A/B Lecture Notes - Lecture 4: Phylogenetic Tree, Koala, Echidna
Document Summary
1. 2 million species of eukaryote identified: many more species that have not been described than those that have. Most recent common ancestor (mrca) for a given group(s), given a phylogenetic tree: only one luca, many mrcas, mrca is only 3000 years old. Why the idea that humans are descended from chimps is inaccurate: chimps and bonobos are our closest living relatives, we are not descended from chimps (not our ancestorsmore like cousins). Order of main branching events in tree of life (dates not testable): chimps, gorillas, orangutans (asian great ape, gibbons, old world & new world monkeys, tarsiers, lemurs & lorises. *can be single celled or multicellular: archaea (adaptations to extreme environments, bacteria. Summary: all life on earth is related through common descent, we can trace our ancestry back to luca in just 39 steps, some similarities reflect shared ancestry; other similarities reflect convergence. Cause of global catastrophe associated with mass extinction 65 mya: