How is the movement of matter through the biosphere different from the flow of energy?

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The answer to this question is that matter is recycled in the biosphere, but energy is not. Energy must be continually added to the biosphere in the form of sunlight.

The definition of "biosphere" is the sum total of all living things and their environments on our planet. With the exception of chemotrophs (organisms that can obtain usable energy from geothermal activity) all living things ultimately rely on producers/autotrophs that capture the energy of the sun. These producers transform light energy through the process of photosynthesis, and "store" the energy in the form of complex sugars that they, or the organisms that consume them, can break down in order to use the energy for their life processes. The efficiency of the energy transfer from one organism to the next is approximately ten percent; much of the energy is lost to the system in the form of heat. If energy from the sun was no longer available, life as we know it would no longer be possible. In other words, the energy flow is one way.

Matter, on the other hand, cycles through the living and non-living parts of the biosphere in what are termed biogeochemical cycles. Elementary students study the water cycle--evaporation, condensation, precipitation, and so on. Carbon, nitrogen, phosphorus, and other vital elements cycle through living organisms, the air, soil, rock, etc, and are reused continuously. Other than the small amounts of minerals that arrive on meteorites, what we have here on Earth is all we will have unless we eventually start obtaining and importing materials from other planets.

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