In these cycles, nutrients move from the environment,through organisms, and back to the environment. Carbon is the basic building block of carbohydrates, fats, proteins, nucleic acids, and other organic compounds essential to life. Nitrogen is required to synthesize proteins, and nucleic acids. The abundant form of nitrogen cannot be used directly. The conversion of atmospheric nitrogen gas into other chemical forms useful to plants is called nitrogen fixation.
Lightning also plays a role in converting nitrogen gas.
Phosphorus Cycle -Various forms of Phosphorous is cycled through water, the earths crust, and living organisms. Sulfur Cycle -Sulfur enter the atmosphere from natural sources. Hydrogen sulfide, from active volcanoes, and decay of organic matter by anaerobic decomposers. Sulfur dioxide from active volcanoes. Particulate sulfate from sea spray.