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Lecture 6- January 17th - Earth's Life Support Systems II...

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January 17, 2012 Earth’s Life- Support Systems II There was a crisis when free oxygen was introduced in atmosphere 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 this ability to make food from light (using sunlight) o There was not a lot of oxygen in the atmosphere because most oxygen was rusting the iron + lots of reactions, thus very little was in atmosphere o Eventually oxygen began to accumulate in the atmosphere o All organisms that are living in water rely on oxygen o Only process for getting it into the atmosphere is photosynthesis The plant matter is available for humans to eat Energy from the sun gets locked into these plants When 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 indirectly When 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 don’t get all that energy in the apple- bunch of waste o we see this occurring every step of the way in a food web Food Webs and Trophic Levels
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each level of food chain is known as trophic level herbivores eat the producers and are in turn source of energy for higher level consumers (carnivores) decomposers will feed on all these organisms after they die each time you move from one form of energy to another there is waste 1 st trophic level: have the producers (plants): take sunlight and produce organic matter whoever eats the 1 st trophic level is the 2 nd trophic level called primary consumers (herbivores) the 3 rd trophic level eats the 2 nd
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