History of Life

History of Life - History of Life Fossils Remains of...

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22/01/2008 17:31:00 Fossils Remains of organisms found in rocks Fossil records are largely incomplete o Special circumstances are required. Hard parts (bone, shell) Lack of Oxygen to prevent decay o Microscopic fossils exists but are very rare Age o Relative Age This layer is older than this layer Easy to determine. New rock goes on top of old rock. Strata o Absolute age Fossil is X million years old Much more difficult to determine Radioactive isotopes Spontaneous decay occurs at a predictable rate  (Half-Life) o Carbon-14 dating Half life of C-14 is 5,700 years Limits effective dating to  <50,000 years C-14 is produced in the upper  atmosphere Decays to common C-12 Production and decay results in  equilibrium Living organisms are constantly  taking up carbon from the  atmosphere, keeps constant ratio. Half-lives of elements vary widely, C-14 vs. 
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History of Life - History of Life Fossils Remains of...

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