the circulation of substances through living organisms from or to the environment

the water that is beneath the Earth's surface

the continuous movement of water between the atmosphere, the land, and the oceans

the process by which plants release water vapor into the air through stomata; also the release of water vapor into the air by other organisms

 
the movement of carbon from the nonliving environment into living things and back 

the process in which nitrogen circulates among the air, soil, water, plants, and animals in an ecosystem

the process by which gaseous nitrogen is converted into ammonia, a compound that organisms can use to make amino acids and other nitrogen-containing organic molecules

bacteria that convert atmospheric nitrogen into ammonia

the process by which nitrites and nitrates are produced by bacteria in the soil

the formation of ammonia compounds in the soil by the action of bacteria on decaying matter

the liberation of nitrogen from nitrogen-containing compounds by bacteria in the soil 

the cyclic movement of phosphorus in different chemical forms from the environment to organisms and then back to the environment