B151xF07_L06EvolHist

B151xF07_L06EvolHist - Georgia Tech School of Biology...

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Biology 1510/1511 Georgia Tech School of Biology Fall 2007 History of Earth and Life Earliest traces of life Atmospheric O 2 Banded iron formations Fossil record Evolutionary radiation and extinction events For a good overview of Earth history, see: Historical Geology Website (GPC)
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Biology 1510/1511 Georgia Tech School of Biology Fall 2007 Early Life, Photosynthesis and O 2 The largest pollution event in Earth history! Canfield (2005) Ann. Rev. Earth Planet. Sci. 33: 1-36 Geochemical and fossil evidence for early activity of photosynthetic cyanobacteria. Relative abundance of Banded Iron Formations through time
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Biology 1510/1511 Georgia Tech School of Biology Fall 2007 Banded Iron Formations Under anoxic conditions, Fe 2+ is soluble in seawater. When O 2 is present, Fe 2+ is oxidized to Fe 3+ , which is much less soluble: 4Fe 2+ + O 2 + 4H 2 O 2Fe 2 O 3 (s) + 8H + Fe 2+ is introduced to the ocean from mid ocean ridges and continental weathering. Early photosynthetic organisms effectively titrated the ocean of soluble (reduced) Fe. Banded iron formations formed extensively between 3.7 and 1.8 Ga and contain virtually all the commercially exploitable iron ore on Earth.
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Biology 1510/1511 Georgia Tech School of Biology Fall 2007 Banded Iron Formations (Image courtesy of Dr. Pamela Gore, Georgia Perimeter College) (Hayes, 2002, Nature 417: 127-128)
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