Carbon Cycle represented by the lion in the plate. 1. Energy flows from the sun in to the Respiration takes place in cells of the biosphere, but nutrients do not enter the primary and secondary consumers, and biosphere from and outside source. Essentially, carbon is released back onto the the same pool of nutrients has circulated for environment as carbon dioxide. the billions of years that the Earth has been in 6. When the primary and secondary existence. Some nutrients, called consumers die, their organic matter enters macronutrients, are used by organisms in large the soil through he process of decay. It is quantities. Macronutrients include carbon, broken down by the decomposers, or hydrogen, oxygen, nitrogen, and phosphorous; detritus feeders, which are small animals micronutrients include iodine, iron, zinc, and and microorganisms that subsist on some others. decaying matter such as fallen leaves, dead 2. Both macronutrients and micronutrients bodies, and animal waste. Earthworms, are recycled; they are passed back and forth mites, centipedes, insects, and crustaceans between living and nonliving components of the ecosystem in processes that we call are detritus feeders. Thus, respiration of biogeochemical cycles. detritus feeders also returns carbon to 3. Materials are incorporated into organic the atmosphere. compounds by producers. Producers are 7. Throughout history, much of the then consumed by primary consumers who carbon has been converted to fossil fuel. are consumed by secondary consumers, and High pressure and temperature transform decomposers are ultimately responsible for carbon-carbon organic matter into coal, oil, releasing the material back into the and natural gas. Fossil fuel processing nonliving environment. follows. There are many uses for fossil 4. We will begin our study of the carbon fuels. Some power plants, generate cycle with the atmosphere, which is the electricity using fossil fuels and Earth’s major reservoir of carbon, in the automobiles are powered by gasoline. The form of carbon dioxide. Carbon enters the products of combustion of fossil fuels biotic (living) part of the ecosystem include carbon dioxide, and other carbon through photosynthesis. Plants of the compounds that enter the atmosphere. forest take the carbon in carbon dioxide Carbon also enters the environment from and uses it in organic compounds such as the burning of wood and plants that occurs glucose, starch, cellulose, and other during a forest fire carbohydrates. Respiration in plants 8. A final aspect of the carbon cycle that returns carbon dioxide to the atmosphere; we will examine is exchange with oceans. an arrow shows this process Some carbon dioxide from the air dissolves 5. Plants are primary producers. In the in oceans and combines with calcium to course of plant consumption, carbons form calcium carbonate, which is passes into primary consumers, animals. incorporated into the shells of mollusks and When animal consumption occurs, or when other creatures. When these shells decay, the primary consumer is eaten, carbon they transform into limestone, which, over passes to a secondary consumer, time, dissolves as it is exposed to water. Carbon is released from the limestone and may return to the atmosphere

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