Nitrogen Cycle

The process in which nitrogen circulates and is recycled is called

• The nitrogen cycle

• The carbon cycle

• The water cycle

• The phosphorus cycle

How much of the atmosphere is composed of nitrogen gas?

• 87%
• 38%
• 78%
• 21%

What converts nitrogen gas into a usable form for plants and animals?

• bacteria

• rain

• fungi

• car exhaust

This can transform nitrogen in the atmosphere into a usable form of nitrogen

• rain

• ice

• lightning

• sun

Where can nitrogen fixing bacteria be found (2 right answers)

• Free living in the soil

• under the leaves of flowering plants

• in the atmosphere

• living on the nodules of certain plants

Round structures on the roots of certain plants

• lichens

• commensals

• cataracts

• nodules

What is the role of denitrifying bacteria

• change nitrate back into nitrogen gas

• change nitrogen gas into nitrate

• absorb carbon dioxide in the soil

• release oxygen gas into the atmosphere

What is the role of decomposing bacteria in the nitrogen cycle?

• change Nitrogen gas into Nitrate

• Return the nitrogen compounds to the soil

• Turn nitrogen into water

• Turn nitrate into nitrogen gas

According to this diagram, plants absorb

• nitrates

• nitrogen fixing bacteria

• animals

• decomposers

The process by which waste and dead organisms release nitrogen back into the soil to be used again.

• Decomposition
• Fixation
• Denitrification
• Sublimation