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Biogeochemical Cycles

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Biogeochemical Cycles

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    1. Biogeochemical Cycles Biogeochemical cycles--the cycles in which nitrogen, carbon, and other inorganic elements of the soil, atmosphere, etc. of a region are converted into the organic substances of animals or plants and released back into the environment. The amount of these elements on earth never changes. The elements are reused over and over again. The elements move between the biotic (living) and abiotic (nonliving) parts of the biosphere.

    2. Carbon Cycle

    3. Carbon Cycle Carbon is found in all living things. It exists in the atmosphere as carbon dioxide. Plants and other autotrophs remove carbon dioxide from the air and use it to make carbohydrates (sugars). Heterotrophs eat these sugars and perform cellular respiration. The carbon dioxide is released back to the atmosphere. Some of the the carbon is used to build the organisms. Once organisms die, decomposers break down their bodies and the carbon is returned to the air as carbon dioxide. Combustion or burning also releases large amounts of carbon dioxide into the air.

    4. Water Cycle

    5. Water Cycle Three basic process are involved: Evaporation—sunlight helps to convert liquid water to vapor. Cellular respiration also releases water vapor as does combustion. Transpiration releases water vapor from the leaves of plants. Condensation—water vapor loses heat and becomes liquid water. Precipitation—water falls from the atmosphere as rain, snow, sleet, or hail.

    6. Nitrogen Cycle

    7. Nitrogen Cycle Nitrogen is necessary for building proteins and DNA. 78% of the air is composed of nitrogen gas (N2). Most living things cannot break the bond between the 2 N atoms and therefore cannot use nitrogen gas. Bacteria in the soil and bacteria living on the roots of certain plants convert the N2 into usable forms of nitrogen. This process is called nitrogen fixation. Plants use this nitrogen for their needs. Animals acquire their nitrogen by eating these plants or by eating other animals. When organisms die, the nitrogen in their bodies is returned to the environment through a process called denitrification. Bacteria convert nitrogen back to N2 which returns to the air.

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