Nitrogen Cycle and Its Impact

What percentage of the molecules in Earth's atmosphere is made of nitrogen atoms bonded together (N₂)?

• 50%

• 60%

• 80%

• 90%

What is the form of nitrogen that plants commonly use?

• Ammonium (NH₄⁺)

• Nitrite (NO₂⁻)

• Nitrate (NO₃⁻)

• Nitrogen gas (N₂)

How do plants and animals obtain nitrogen?

• Directly from the atmosphere

• By consuming other organisms

• Through photosynthesis

• By absorbing sunlight

What process converts ammonium salts into nitrite and then nitrate?

• Photosynthesis

• Mineralization

• Denitrification

• Respiration

What human activity is causing increased nitrate levels in waterways?

• Deforestation

• Use of nitrogen-rich fertilizers

• Urbanization

• Mining

What is the process called when dissolved nitrate is returned to the atmosphere by bacteria?

• Nitrification

• Denitrification

• Ammonification

• Assimilation

What happens to plants when they use up the nitrate supply?

• They grow faster

• They die

• They produce more seeds

• They become dormant

What effect does increased nitrate levels have on the food chain?

• Decreases plant growth

• Increases herbivore population

• Reduces soil fertility

• Causes plant diseases

What is one way humans alter the nitrogen cycle besides using fertilizers?

• Planting more trees

• Burning fossil fuels

• Reducing water usage

• Increasing biodiversity

What waste product from livestock farming affects the nitrogen cycle?

• Carbon dioxide

• Methane

• Nitrogen

• Sulfur