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The Rise of Oxygen and Ozone.docx

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Life Sciences
Luc Bernier

Jan 23, 2013 2HO3: The Rise of Oxygen and Ozone Life & the Early Atmosphere: - About 3.5 bya, O2 emerged - The stromatolites have bubbles of oxygen coming out of them and the oxygen moving up through the water into the atmosphere - Possible that early stromatolites did not produce O2 Oxygenic Photosynthesis: - Carried out today by higher plants and algae - Requires light/energy 6CO2 + 6H2O  C6H12O6 + 6O2 Anoxygenic Photosynthesis: - No oxygen released during photosynthesis - Light/energy is required for this process to occur o Example:  Photosynthetic bacteria and blue green algae are capable of undergoing this pathway  Notice that it requires H2S (hydrogen sulphide)  Since it needs light it must occur on the surface of the earth CO2 + H2S  (CH2O) + 2S0 + H2O Chemosynthesis on Early Earth: - Many early microfossils related to microbes currently found near hydrothermal vents - From the materials rising from the cores of the earth o Doesn't require light, perhaps not even O2 CO2 + 4H2S + O2  (CH2O) + 4S0 + 3H2O Production of Methane: - Primitive methanogens would have survived in H2 rich atmosphere of early earth o Organisms that are capable of this are found in the kingdom Archaea o Methane was really abundant in the early atmosphere CO2 + 4H2  CH4 + 2H2O - If you look at Titan (Saturn’s moon), you can get a good representation of what early earth would have looked like o Lots of methane, this could explain why some of the earliest life forms on earth are methanogens Jan 23, 2013 Modern N Cycle in the Ocean: - Phytoplankton played a key role in transforming N2 into others forms which can be used N Cycling on Early Earth: - Early microbes could not fix N2 form the atmosphere o Possible ways that N2 could have gotten into our water cycle includes:  N2 + O2  2NO (lightening)  HNO3  H + NO3 −
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