The Nitrogen Cycle

Name

What is the name of the process that changes nitrogen in the air into a form that plants can use?

• Photosynthesis
• Nitrogen fixation
• Denitrification
• Decomposition

What happens to nitrogen when plants and animals die?

• It is lost forever.
• It is released back into the air.
• It is stored in their bodies.
• It is released back into the soil.

Besides bacteria, what else can fix nitrogen?

• Sunlight
• Wind
• Humans
• Animals

What percentage of the air we breathe is made up of nitrogen?

• 18%
• 78%
• 38%
• 58%

What is the name of the process that changes ammonia into nitrates?

• Nitrogen fixation
• Ammonification
• Denitrification
• Nitrification

What do plants use nitrogen for?

• To make flowers
• To make roots
• To make food
• To make stems

What happens to nitrates during denitrification?

• They are absorbed by plants.
• They are released back into the atmosphere.
• They are converted into ammonia.
• They are stored in the soil.

What is the main source of nitrogen for animals?

• The air
• The soil
• Plants
• Water

Chlorophyll is a green substance that plants use to make food through photosynthesis.

• True
• False