Understanding the Nitrogen Cycle

What percentage of our atmosphere is made up of nitrogen gas (N2)?

• 78%

• 21%

• 10%

• 5%

What is the term used for the process that moves nitrogen from the air to the soil?

• Ammonification

• Nitrification

• Denitrification

• Nitrogen fixation

Which bacteria are responsible for breaking the triple bond of nitrogen gas to make it usable?

• Ammonifying bacteria

• Denitrifying bacteria

• Nitrifying bacteria

• Nitrogen-fixing bacteria

What is the form of nitrogen that plants can directly assimilate to make biological molecules?

• Carbon dioxide

• Nitrite

• Nitrogen gas

• Ammonia

What process converts ammonia into nitrates?

• Denitrification

• Assimilation

• Nitrification

• Nitrogen fixation

Which of the following is NOT a product of nitrification?

• Nitrogen gas

• Nitrate

• Ammonia

• Nitrite

What happens during denitrification?

• Nitrates are converted into nitrogen gas

• Ammonia is converted into nitrates

• Nitrogen gas is fixed into ammonia

• Ammonia is released from decomposing organisms

Tags

NGSS.HS-LS2-3

Where do nitrogen-fixing bacteria typically reside?

• Inside animal intestines

• On the surface of leaves

• In the atmosphere

• In the soil and root nodules of legumes

Tags

NGSS.MS-LS2-3

What is the role of ammonia in the nitrogen cycle?

• It is used directly by animals for nutrition

• It acts as a soil pollutant

• It is released into the atmosphere as a gas

• It is assimilated by plants to make proteins and DNA

Which environment is most suitable for nitrification?

• Highly acidic soils

• Dry and arid regions

• Waterlogged soils

• Well-aerated soils