The nutrient cycle The process of recycling substance necessary for life. It includes: The carbon cycle The nitrogen cycle The phosphorous cycle The water cycle

Carbon Cycle This is the cycling of carbon between carbon dioxide and organic molecules The main component of organic compounds is carbon. Carbon passes to other organisms through the food chain. It then returns to the earth through respiration, excretion, or decomposition after death. Coal and other fossil fuels can form from decomposing organic matter.

Nitrogen Cycle Most abundant gas at 78% The nitrogen cycle converts nitrogen into ammonia, nitrite, and then nitrate so that plants and animals may use it. Nitrogen fixation is the conversion of nitrogen gas into nitrate by several different bacteria. This process releases nitrogen from the atmosphere into the soil for plants to use Plants use this nitrogen to synthesize nucleic acids and proteins. The nitrogen passes through the food chain to other animals.

Nitrogen cycle continued Decomposers release ammonia as they break down plant and animal remains. The bacteria then convert nitrate and nitrite into nitrogen gas and is released into the atmosphere.

Phosphorous Cycle Phosphates are introduced into the soil through weathering, or breakdown of sedimentary rocks. Plants and fungi absorb the phosphate. The phosphate then moves through the food chain via consumption. It then returns to the soil as waste or decomposed material

Water Cycle Circulates freshwater between the earth’s surface and the atmosphere. The sun provides heat to start evaporation of water molecules. The sun also provides the energy to power winds and ocean currents. Respiration also provides water evaporation to the atmosphere. The water cools to form clouds which then precipitate.