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Lecture 6

Lecture 6- January 17th.docx

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Maureen Padden

January 17 2012Earths Life Support Systems IIThere was a crisis when free oxygen was introduced inatmosphere o Tiny fraction of organisms could deal with it o For a good billion of years organisms were not used to the free oxygen atmosphere o After a while a bunch of species developed thisability to make food from light using sunlight o There was not a lot of oxygen in the atmospherebecause most oxygen was rusting the ironlotsof reactions thus very little was in atmosphere o Eventually oxygen began to accumulate in theatmosphere o All organisms that are living in water rely onoxygeno Only process for getting it into the atmosphere is photosynthesisThe plant matter is available for humans to eatEnergy from the sun gets locked into these plantsWhen this plant eg Apple from the tree is eaten release chemical energy and use it We are all fed by sunlight because what we eat is fed by sunlight either directly or indirectlyWhen converting from one form of energy to another there is waste o Not a purely efficient process When an individual eats a plant releases the energy by breaking the chemical bonds o once bonds are broken energy is released o we dont get all that energy in the apple bunch of wasteo we see this occurring every step of the way in a food webFood Webs and Trophic Levelseach level of food chain is known as trophic level
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