BSC 196 Lecture Notes - Lecture 9: Phanerozoic, Geologic Record, Hadean
Document Summary
Geologic record is divided into four eons: First 3 eons comprise first four billion years. Oldest known fossils are stromatolites, rocks formed by accumulation of sedimentary rock on bacterial mats. By 2. 7 bya o2 began accumulating in the atmosphere. Lead to extinction of organisms unable to breath oxygen. Endosymbiont theory: mitochondria and plastids were early small prokaryotes living within larger host cells. Prokaryotic ancestors of chloroplasts and mitochondria might have been undigested prey or parasites. Host gained aerobic capacity (ability to use oxygen) Serial endosymbiosis: mitochondria were absorbed first, then plastids. All eukaryotes have mitochondria but not plastids. Inner membranes are similar to plasma membranes of prokaryotes. History of life has seen rise and fall of many groups of organisms. Influenced by speciation rates and extinction rates. Fossil record shows most species that ever existed are now extinct. Extinction has increased at times and caused mass extinction events. Lead to global warming and ocean acidification.
