Nitrogen in the Earth's Atmosphere

How much of the atmosphere is composed of nitrogen gas?

• 87%
• 38%
• 78%
• 21%

How do plants get the nitrogen they need?

• from the air
• from the soil or water in which they live
• from the Sun
• from broken-down rocks

Why do all organisms need nitrogen?

• To live and grow 
• To build phosphorus
• To make oxygen levels grow
• To help blood circulate better

Nitrogen fixing bacteria, lives in nodules on the root of a plant called

• Broccoli
• Legumes
• Beats
• Carrots

The swelling on the roots of a soybean are called

• Noodles
• Nitrogen
• Nodules
• Legumes

What converts some atmospheric nitrogen into nitrates that organisms can use?

• Sun
• Rain
• Thunder
• Lighting

Which of the following describes the role of nitrogen-fixing bacteria in the nitrogen cycle? Nitrogen-fixing bacteria convert

• nitrates intro nitrogen gas
• ammonia into proteins
• nitrogen gas into ammonia
• proteins into nitrates

Animals obtain the nitrogen they need directly from the

• soil in their habitat
• air they breathe
• plants they eat
• bacteria living within them

Growing legumes such as alfalfa or soy beans increases

• denitrification
• nitrogen fixation
• ammonification
• ammonium oxidation

A particular golf course is using large amounts of nitrogen fertilizer. What process could move this nitrogen into a local stream?

• volatilization
• nitrogen fixation
• runoff
• ammonification