Slide 3:

What is the nitrogen cycle?

• The process of converting oxygen into carbon dioxide

• The movement of atoms and molecules containing nitrogen between sources and sinks

• The transformation of water into vapor

• The cycle of carbon through the atmosphere

Slide 4:

What is the main reservoir of nitrogen on Earth?

• Oceans

• Soil

• Atmosphere

• Plants

Slide 4:

Why is most atmospheric nitrogen not usable by plants and animals?

• It is in the form of N2 gas.

• It is toxic to living organisms.

• It is only available in solid form.

Slide 5:

What is the process of converting N₂ gas into a form usable by plants called?

• Photosynthesis

• Fixation

• Respiration

• Denitrification

Slide 5:

What role do cyanobacteria play in nitrogen fixation?

• They fix nitrogen in the soil

• They fix nitrogen in the ocean

• They decompose organic matter

Slide 5:

What happens to the excess ammonia secreted by bacteria?

• It is released into the atmosphere

• It is taken up by plants

• It is used by animals

Slide 6:

What is the process called where humans convert N₂ gas into ammonia (NH₃) or nitrate (NO₃⁻)?

• Synthetic fixation

• Natural fixation

• Atmospheric fixation

Slide 6:

What role do synthetic fertilizers play in agriculture?

• They reduce crop yields

• They are not used in agriculture

• They help increase crop yields

Slide 6:

Which natural phenomena can create nitrate ions that are deposited when it rains?

• Photosynthesis

• Lightning and combustion

• Erosion

Slide 7:

What is the process called where NH₄⁺ is converted into nitrite (NO₂⁻) and then nitrate (NO₃⁻) by soil bacteria?

• Denitrification

• Nitrification

• Ammonification