Nitrogen Cycle Quiz

What percentage of the Earth's atmosphere is made up of nitrogen gas (N2)?

• 95%

• 78%

• 21%

• 50%

Which type of bacteria is responsible for breaking the triple bond of nitrogen gas?

• Nitrogen-fixing bacteria

• Ammonifying bacteria

• Denitrifying bacteria

• Nitrifying bacteria

What is the process called when nitrogen gas is converted into ammonia?

• Assimilation

• Nitrification

• Nitrogen fixation

• Denitrification

Which compound is formed when nitrogen-fixing bacteria add hydrogen to nitrogen gas?

• Nitrogen gas (N2)

• Ammonia (NH3)

• Nitrate (NO3-)

• Nitrite (NO2-)

What is the process of converting ammonia into nitrates called?

• Ammonification

• Nitrification

• Denitrification

• Assimilation

Which type of bacteria converts nitrates back into nitrogen gas?

• Nitrogen-fixing bacteria

• Ammonifying bacteria

• Denitrifying bacteria

• Nitrifying bacteria

In which type of environment does denitrification occur best?

• Mountainous regions

• Desert soils

• Waterlogged soils

• Well-aerated soils

What is the process called when plants take up ammonia to make biological molecules?

• Denitrification

• Ammonification

• Assimilation

• Nitrification

What happens to nitrogen when an animal eats a plant?

• It becomes nitrogen gas

• It moves to the animal

• It is converted into ammonia

• It is released into the atmosphere

What is the process called when decomposing organisms return nitrogen to the soil as ammonia?

• Nitrification

• Denitrification

• Ammonification

• Assimilation