Energy with less ordered forms energy ows into an

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Unformatted text preview: the entropy (disorder) of the universe Heat Chemical energy (a) First law of thermodynamics CO2 + H 2O (b) Second law of thermodynamics •  Living cells unavoidably convert organized forms of energy to heat •  Spontaneous processes occur without energy input; they can happen quickly or slowly •  For a process to occur without energy input, it must increase the entropy of the universe Biological Order and Disorder •  Cells create ordered structures from less ordered materials •  Organisms also replace ordered forms of maQer and energy with less ordered forms •  Energy flows into an ecosystem in the form of light and exits in the form of heat Why does the evoluGon of more complex organisms not violate the second law of thermodynamics? •  Entropy (disorder) may decrease in an organism, but the universe’s total entropy increases Equilibrium and Metabolism •  Reactions in a closed system eventually reach equilibrium and then do no work •  Cells are not in equilibrium; they are open systems experiencing a constant flow of materials •  A defining feature of life is that metabolism is never at equilibrium •  A catabolic pathway in a cell releases free energy in a series of reactions The free-en...
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