Chapter 21 History of Life on Earth

Chapter 21 History of Life on Earth - Chapter 21 Dating...

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Chapter 21 Dating Ancient Events - formalization of age of rocks done by Steno - Strata- layer of rock - Older strata are deeper - Fossils of similar organisms found in widely separated places on earth - Certain organisms found in younger layers - Organisms in more recent strata are more similar to current organisms Radioisotopes - ½ life of isotopes allows one to date certain things Radioisotopes dating methods - sedimentary rocks formed from materials from various time periods; unreliable radiodating methods - when combined with fossil analysis, powerful analysis of geological time period - paleomagnetic dating- using Fe orientation to determine time period 21.2 Earth’s continents and Climates - crust made up of plates, make up lithosphere - lay on magma - movements of lithospeptic plates leads to continental drift Molecular Oxygen steadily rising in atmosphere - originally no PO2 in atm - certain bacteria developed photosynthesis, used CO 2 to reduce to organic compounds - cyanobacteria – O 2 making bacteria, preserved in stranatolites - at first, O 2 was poisonous - ability to be aerobic made those so fit in a high PO 2 enviorment - larger cells have less SA/V ratio, need higher PO 2 - only unicellular prokaryotes lived in earth for more than 2 billion yrs Earth has switch from hot/humid to cold/dry Enviorment
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This note was uploaded on 09/15/2009 for the course BIOE 20c taught by Professor Marinovic during the Summer '09 term at University of California, Santa Cruz.

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Chapter 21 History of Life on Earth - Chapter 21 Dating...

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