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The Rise of Oxygen and Ozone.docx

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Department
Life Sciences
Course
LIFESCI 2H03
Professor
Luc Bernier
Semester
Winter

Description
rd January 23 , 2013 Life Sci 2H03: Environmental Life Sciences The Rise of Oxygen and Ozone The Rise of Oxygen and Ozone - life on earth: about 3.5 Gyr ago Life and the Early Atmosphere - fossils of stramatolites were capable of the same activities of the current ones - possible that early stromatolites may no have been producing O 2 - other photosynthetic pathways were oxygen is not necessarily produced Oxygenic Photosynthesis - carried out today by higher plants and algae - 6CO +26H O 2 C H O 6 612 6 2 Anoxygenic Photosynthesis - no oxygen released during photosynthesis - 6CO +2H S 2 (CH O) +22S + H O0 2 - blue, green algaes: under conditions where there is no oxygen - microbes - needs to happen at Earth’s surface as it requires light Chemosynthesis on Early Earth - many early microfossils: related to microbes from hydrothermal vents - uses materials rising from the core of the Earth - CO 2 4H S 2 O  2CH O) + 42 + 3H O 0 2 - Earliest life forms that surfaced in the deep oceans are believed to have been chemosynthetic as Earth was devoid of oxygen Production of Methane - primitive methanogens would have survived in H -rich at2osphere of Early Earth - CO + 4H  CH + 2H O 2 2 4 2 - Found for the most part in the kingdom Archaea - Corresponds to some of the deepest branches/earliest life forms on earth - Titan, one of the moons of Saturn, is what Early Earth would have resembled, high in methane Modern N Cycle in the Ocean - most organisms are not able to process oxygen + - - - NH ,4NH , N3 , N2 can b3 used - Microbes can transform nitrogen in the form that can be used by organisms N Cycling on Early Earth - early microbes could not fix N fro2 the atmosphere - N 2 O 22NO - HNO  H +NO + - 3
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