Can release carbon dioxide gas back into the atmosphere.

Directly creates fossil fuels.

Fixes carbon atoms in the soil,

Removes dissolved carbon dioxide from lakes and rivers.

Increases the levels of CO₂ in the atmosphere.

Decreases the levels of CO₂ in the atmosphere.

For cellular respiration.

For effective removal of CO₂ gas.

For synthesis of all families of macromolecules.

For synthesis of lipids and carbohydrates only.

Nitrites

Ammonia

Nitrates

N_{2 gas}

denitrification.

nitrogen fixation.

ammonification.

cellular respiration.

Turn nitrogen gas into nitrates so that plants can synthesize amino acids.

Turn nitrates into nitrites so that nitrogen fixing bacteria can synthesize DNA.

Returns nitrogen into the atmosphere in the form of N₂ gas.

Use phosphorus as fertilizer.

Carbohydrates

Nucleic acids

Amino acids

Triglycerides and steroids

It is the only nutrient that is used as fertilizer for crops.

It is the only cycle that helps synthesize lipids.

It does not cycle through the atmosphere.

It is the only element that can be dissolved in water.

Inorganic phosphate rock

Runoff

Marine sediments

Phosphates in soil

be used to synthesize lipids.

be absorbed directly by phosphate rock.

be decomposed and returned to large bodies of water.

provide nutrients for algal blooms, which can cause eutrophication.