Disclosure+4+Discussion


 * Disclosure 4**
 * A closed system self-regulates gains and losses of energy; natural ecosystems resemble a closed system with respect to energy and nutrient cycles. To best understand the concept of energy flow, Ed recommends that you investigate nutrient cycling. Limit your efforts to Nitrogen, Carbon and water cycles; know the chemical forms in the various parts of the cycles. Identify where gains and losses of nutrients occur.**

__Closed Systems__ An organisational approach that does not accept input from the external environment. A Closed System does not gain or loose energy or material. **Closed ecological systems** (CES) are ecosystems that don't rely on matter exchange with any part outside the system.

__Gains and Losses of Energy__ Gains and losses in soil nutrients occur as a result of combustion of organic matter on and near the soil's surface.

__Nutrient Cycling__ Plants need nutrients from the soil to grow. The majority of soil nutrients come from the breakdown of mineral-bearing rocks and from organic matter, which comes from the decomposition of plants and animals. The nutrients that plants get from the soil are stored in all plant tissues, such as leaves, stems and flowers. When these tissues fall to the ground they start to break down, and together with decomposing dead insects, dead animals and animal feces, they are eventually re-incorporated into the soil by rainfall and earthworms. There, the organic matter is further broken down and slowly transformed to become nutrients that are available to growing plants (and the cycle continues).

__Chemical Forms__
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__Nitrogen, Carbon and Water Cycles (Energy Cycles)__


 * Nitrogen Cycle**

All life requires nitrogen compounds. Air, which is 79% nitrogen gas is the major reservoir of nitrogen, but most organisms can't use it in this form. Plants must secure their nitrogen in "fixed form", ie., incorporate in compounds such as nitrate ions (NO3-), ammonia (NH3), urea (NH2)2CO. As for animals, they secure their nitrogen (and all other) compounds from plants (or animals that have fed on plants)**.**
 * Four processes participate in the cycling of nitrogen through the biosphere:**
 * 1) **nitrogen fixation** (the biological process by which nitrogen (N2) in the atmosphere is converted into ammonia.)
 * 2) **decay/nitrogen mineralization ** ( process in which organic forms of nitrogen (eg, proteins in dead plant material) are converted by microbes to inorganic forms of nitrogen (eg ammonium and nitrate))
 * 3) **nitrification** (The conversion of ammonia (NH3) to nitrate (NO 3-))
 * 4) **denitritication** (the process of degrading nitrogenous compounds and releasing nitrogen)

Microorganisms play major roles in all four of these.



Another way nitrogen enters the cycle is as inorganic nitrogen from the atmosphere and factories. The concern with these forms is that the incremental amount of nitrates they add to the nitrogen cycle may threaten groundwater.


 * Rain storms contribute atmospheric nitrogen through rain drops that reach the soil.
 * Legumes, such as soybeans, alfalfa and clovers, are plants that can convert atmospheric nitrogen into plant-usable nitrogen.
 * Factories that produce nitrogen fertilizers add nitrogen to the soil when farmers and gardeners "feed" their crops.
 * Nitrogen in sewage sludge from municipal waste plants can be used to fertilize farm fields


 * Carbon Cycle**

Carbon and other elements of matter within ecosystems, being used again and again as they travel through food chains, soil, the atmosphere and water. Energy enables carbon to move through these different components of an ecosystem, however, it is important to note that carbon CYCLES WITHIN a system and energy **FLOWS THROUGH** an ecosystem.



**Water Cycle**

As the water evaporates, vapors rise and condense into clouds. The clouds move over the lan, and precipitation falls in form of rain, ice, or snow. The water fills strems and rivers, and eventually flows back into the oceans where evaporation starts the process again. Water's state (solid, liquid or gas) is determined mostly by temperature. Although water continuously changes states from solid to liquid to gas, the amount of water on Earth remains constant There is as much water now as there was hundreds of millions of years ago.