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Lecture24_Biosphere3

Lecture24_Biosphere3 - EAS 1600 Introduction to...

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EAS 1600 Introduction to Environmental Sciences ____________________________ Class 27 - The Biosphere: Part 3 Metabolic Processes Evolution of Biosphere and Earth System ________________________________ In this lecture we discuss the various chemical pathways or strategies organisms use to survive, and the role these pathways play in the Earth System. Biogeochemical cycle involving N ¾ photosynthesis: 5CO 2 + 5H 2 O + 5 h ν Æ 5“CH 2 O” + 5O 2 ¾ denitrification: 4HNO 3 + 5"CH 2 O” Æ 2N 2 + 5CO 2 + 7H 2 O ¾ nitrogen fixation: 2N 2 + 6H 2 O Æ 4NH 3 + 3O 2 ¾ nitrification 4NH 3 + 8O 2 Æ 4HNO 3 + 4H 2 O Biogeochemical cycle involving C ¾ photosynthesis: CO 2 + H 2 O + h ν Æ “CH 2 O” + O 2 ¾ respiration “CH 2 O” + O 2 Æ CO 2 + H 2 O Biogeochemical cycle involving S (simple) ¾ photosynthesis: 2CO 2 + H 2 S + 2H 2 O+ h ν Æ 2"CH 2 O” + H 2 SO 4 ¾ sulfate reduction H 2 SO 4 + 2"CH 2 O” Æ 2CO 2 + H 2 S + 2H 2 O Biogeochemical cycle involving S (not simple) ¾ photosynthesis: 2CO 2 + 2H 2 O + h ν Æ 2“CH 2 O” + 2O 2 ¾ sulfate reduction H 2 SO 4 + 2"CH 2 O” Æ 2CO 2 + H 2 S + 2H 2 O ¾ H 2 S oxidation in atmosphere can you write down the reaction that is needed to balance the cycle? Now let’s try to understand: 1. How these various metabolic processes evolved on the earth; and 2. How they, in turn, influenced the evolution and development of the earth system itself.
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