The Nitrogen Cycle

What is nitrogen used for?

• nitrogen in the air is converted into nitrates in the soil.

• nitrate ions are taken up by plants and converted into amino acids and proteins.

• These molecules are eaten by consumers and therefore circulate food webs.

The Nitrogen Cycle - nitrogen fixing bacteria

• bacteria that converts nitrogen gas into nitrogen compounds (nitrates), that can be used by plants.

what are nodules?

• nitrogen fixing bacteria found on the roots of leguminous plants.

• (nitrogen-fixing bacteria can also live free in the soil)

The Nitrogen Cycle - decomposers

• when living organisms die, they are broken down by micro-organisms.

• large, complex molecules are broken down and released as smaller molecules.

• nitrogen released as ammonia or ammonium ions.

The Nitrogen Cycle - nitrifying bacteria

• bacteria found in soil.

• convert ammonium ions to nitrates

• nitrates taken up by plant and converted to amino acids and protein.

The Nitrogen Cycle - denitrifying bacteria

• convert nitrates in soil → nitrogen gas

• reverses the activities carried out by other bacteria.

• therefore, denitrifying bacteria reduces valuable nitrates in the soil.