CAS BI 107 Lecture Notes - Lecture 1: Milankovitch Cycles, Continental Drift, Deccan Traps
Document Summary
During the precambrian, life was not particularly complex. Lack of oxygen, presence of toxic gasses, thus primarily anaerobic respiration. Bacteria evolved to strip hydrogen off of hydrogen sulfide - cyanobacteria, then evolved to strip hydrogen off of water. Explosion of morphological diversity, simple, diploblastic, multicellular organisms to bilateral animals, ect. (545 -525 mya) All life was marine in origin, transition from soft body organisms to diversity we see today. Burgess shale - preservation of soft body organisms found in cambrian period. Mass extinction at end, 75% of all animals go extinct. First vascular plants and terrestrial arthropods evolve. First jawed fish, animal groups radiate, forests appear on land. Mass extinction, 75% of marine species go extinct. Extinction that almost wiped off life on earth. 96% of marine species go extinct, oxygen levels drop. Many insects still survive, however, impacted many land organisms as well. Occurred in less than 5 million years.
