Cylces of life

Photosynthesis - how the carbon comes to earth from the atmosphere Cellular respiration - how the carbon is released from plants/animals back into the atmosphere Combustion - when carbon is released into the atmosphere by factories/cars Decomposition - when carbon is released atmosphere by dead plants/animals... some is turned into fossil fuels to be burnt later

Plants and animals must have nitrogen to make proteins and nucleic acids. However, the nitrogen gas is not usable by plants or animals - so the nitrogen cycle must happen to change nitrogen into a usable form through a series of steps. Most of this is done using bacteria & decomposers; however, some nitrogen enters the soil via lightning.

Nitrogen fixation: the process when nitrogen-fixing bacteria in the soil/on plant roots change nitrogen gas into ammonia Ammonification: the process when decomposers break down dead stuff/animal wastes into ammonium Nitrification: the process when nitrifying bacteria change ammonium into nitrates, which is what plants can use Assimilation: when the plants take in the nitrates Denitrification: when denitrifying bacteria take the excess nitrates and turn it back into nitrogen gas

This is the only cycle without an atmospheric portion. Phosphate is released via the weathering of rocks. Plants & some fungi take up phosphorus. Phosphorus moves from producers to consumers via the food web. Phosphorus is released back into the soil when organisms die & decomposers break them down. Phosphorus gets into water via runoff and leaching from the groundwater. Mining and agricultural runoff add to the phosphorus in the environment.