Understanding the Nitrogen Cycle

What percentage of the air is made up of nitrogen?

• 10%

• 78%

• 55%

• 21%

What is the purpose of nitrogen-fixing bacteria?

• To create a toxic environment for plants
• To convert carbon dioxide into oxygen
• To increase the acidity of the soil
• To convert atmospheric nitrogen into a form that plants can use

What role do decomposers play in the nitrogen cycle?

• They fix nitrogen in the air

• They return nitrogen to the soil

• They consume nitrates

• They create oxygen

What does lightning contributes to nitrogen cycle?

• Increases the amount of nitrate in the soil

• Lightning has no impact on the nitrogen cycle
• Lightning converts nitrogen into oxygen
• Lightning directly absorbs nitrogen from the atmosphere

How does burning fossil fuels affect the nitrogen cycle?

• It has no effect

• It increases oxygen levels

• It adds nitrous oxide to the atmosphere

• It removes nitrogen from the soil

What is the result of nitrogen fixing by cyanobacteria in oceans?

• Decrease in aquatic life

• Increase in saltwater

• Provides nitrogen to aquatic animals

• Removes carbon dioxide from water

What happens when there's too much nitrogen in the soil?

• It produces more oxygen

• It attracts more wildlife

• It turns into sand

• It becomes more acidic

What is a negative effect of too much nitrogen in water bodies?

• It increases water clarity

• It promotes fish growth

• It purifies the water

• It acts as a pollutant

How is nitrogen returned to the atmosphere from the soil?

• Through water evaporation

• Via sunlight exposure

• By nitrifying bacteria breaking down nitrates

• Through plant growth

Plants take in nitrogen through _______________, then animals take in nitrogen by ____________

• soil

  eating plants

• Breathing

  Breathing

• stems

  photosynthesis

• leaves

  hunting for prey