Understanding the Nitrogen Cycle

The video explains the nitrogen cycle, highlighting the conversion of atmospheric nitrogen into nitrates through lightning and bacteria. It covers the absorption of nitrates by plants for protein and DNA synthesis, the role of animals in returning nitrogen to the soil, and the decomposition process. The video also discusses denitrifying bacteria that convert nitrates back to nitrogen gas, completing the cycle.

What percentage of the atmosphere is composed of nitrogen?

• 50%

• 78%

• 21%

• 10%

What is the role of lightning in the nitrogen cycle?

• It converts nitrogen gas into oxygen.

• It converts ammonia into nitrites.

• It fixes nitrogen gas into nitrates.

• It breaks down nitrates into nitrogen gas.

Where are nitrogen-fixing bacteria commonly found?

• In the stems of trees

• In the flowers of plants

• In the nodules on the roots of legumes

• In the leaves of plants

What compound do nitrogen-fixing bacteria convert atmospheric nitrogen into?

• Nitrates

• Ammonia

• Nitrites

• Oxygen

What do nitrifying bacteria convert ammonia into?

• Nitrates

• Nitrites

• Carbon dioxide

• Oxygen

How do plants utilize nitrates absorbed from the soil?

• To store energy

• To create glucose

• To make proteins and DNA

• To produce oxygen

What happens to nitrogen when animals urinate?

• It forms new proteins

• It returns to the soil as urea

• It is converted into oxygen

• It is lost to the atmosphere

What role do decomposers play in the nitrogen cycle?

• They fix nitrogen gas into nitrates

• They convert nitrates into nitrogen gas

• They break down dead material into ammonia

• They absorb nitrates from the soil

What is the function of denitrifying bacteria?

• To convert nitrates into nitrogen gas

• To absorb nitrates from the soil

• To convert ammonia into nitrites

• To fix nitrogen gas into ammonia

Why are denitrifying bacteria not beneficial for living plants?

• They increase nitrate concentration in the soil

• They convert nitrates back into nitrogen gas

• They fix nitrogen gas into ammonia

• They produce excess oxygen