1. Abiogenesis  Initially, earth had an oxygen poor atmosphere and acidic oceans  Source of simple organics may have been terrestrial or extraterrestrial  The big questions:  What divides life from non-life?  What gave the energy for the formation of complex organics?  What stimulated self-replication?  How did the cell arise?

2. History of Life Archean eon  3.8- 2.5 bya  Prokayotes arise  Stromatolites date to 3.5 bya  Buildup of oxygen in the atmosphere begins as a result of photsynthesis http://evolution.berkeley.edu/evolibrary/images/stromatolit e_xsection.jpg http://www.ucmp.berkeley.edu/bacteria/oscillatoria2.jpg

3. History of Life Proterozoic eon  2.5 bya- 540 mya  Atmosphere oxygenation accelerates  Eukaryotes appear at 2.1 bya  Endosymbiosis may explain the development of eukaryotes  Multicellular eukaryotes appear 1.2- 1.5 bya; diverse large-bodied organisms appear around 575 mya  Snowball earth event http://cosmosmagazine.com/news/chan ge-ancient-seas-allowed-life-spread/ http://newsimg.bbc.co.uk/media/images/4016 3000/jpg/_40163795_edifossl_bbc_203.jpg

4. History of Life Phanerozoic eon  540 mya- present  Cambrian explosion: sudden appearance of many phyla (arthropoda, annelida, brachiopoda, echinodermata, cnidaria and chordata)  Appearance of bilateral symmetry, triploblastic embryos, and the coelom  Fungi and plants invade land 500 mya  Arthropods colonize land 420 mya  Tetrapods colonize land 365 mya  Whole groups of organisms display periods of success and subsequent falls from dominance

5. History of Life http://theresilientearth.com/files/images/Phanerozoic_Biodiversity.png

6. Mass Extinction Events  Five major mass extinctions (Ordovician, Devonian, Permian, Triassic, Cretaceous)  Seventeen or more minor extinctions Potential causes:  Volcanism  Permian, Triassic, Cretaceous  Sea level disruptions  All of the major five  Asteroid impacts  Cretaceous http://evolution.berkeley.edu/evolibrary/article/history_08

7. Adaptive Radiations  A period of rapid increases in phenotypic diversity in a lineage  Often spurred by extinctions or large evolutionary innovations  Worldwide radiations include those made by prokaryotes as they became photosynthetic, by many organisms as they moved onto land, and by mammals after the Cretaceous extinction event  Regional radiations include those that have occurred on various island chains and Australia http://www.bio.miami.edu/dana/pix/hawaiian_h oneycreepers.jpg

8. Ordering Life  Phylogeny: evolutionary history of a species or lineage  Taxonomy: classifying organisms into groups based on shared characteristics  Species are denoted with a binomial nomenclature http://www.biologycorner.com/resources/orca_taxonomy.gif?054f9e http://www.utexas.edu/features/graphics/2008/tre e/tree3.jpg