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Ecosystems and Communitie1

Ecosystems and Communitie1 - thermodynamics Recall that the...

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Ecosystems and Communities Even if communities do differ in structure, they have some common uniting processes such as energy flow and matter cycling , shown in Figure 17. Energy flows move through feeding relationships. The term ecological niche refers to how an organism functions in an ecosystem. Food webs , food chains , and food pyramids are three ways of representing energy flow. Producers absorb solar energy and convert it to chemical bonds from inorganic nutrients taken from environment. Energy content of organic food passes up food chain; eventually all energy is lost as heat, therefore requiring continual input. Original inorganic elements are mostly returned to soil and producers; can be used again by producers and no new input is required. Energy flow in ecosystems, as with all other energy, must follow the two laws of
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Unformatted text preview: thermodynamics. Recall that the first law states that energy is neither created nor destroyed, but instead changes from one form to another (potential to kinetic). The second law mandates that when energy is transformed from one form to another, some usable energy is lost as heat. Thus, in any food chain, some energy must be lost as we move up the chain. The ultimate source of energy for nearly all life is the Sun. Recently, scientists discovered an exception to this once unchallenged truism: communities of organisms around ocean vents where food chain begins with chemosynthetic bacteria that oxidize hydrogen sulfide generated by inorganic chemical reactions inside the Earth's crust. In this special case, the source of energy is the internal heat engine of the Earth....
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