IGCSE Nitrogen Cycle

What form of nitrogen is most abundant in the Earth's atmosphere?

• Ammonium compounds

• Nitrates

• Nitrites

Which process makes atmospheric nitrogen available to living organisms?

• Photosynthesis

• Nitrogen fixation

• Respiration

• Transpiration

What role do nitrogen-fixing bacteria play in the nitrogen cycle?

• They convert nitrates into nitrogen gas

• They convert nitrogen gas into ammonium compounds

• They decompose organic matter

• They absorb nitrates from the soil

How can nitrogen gas be fixed naturally besides by bacteria?

• Through photosynthesis

• By lightning strikes

• By animal digestion

• Through evaporation

What do plants do with the nitrates absorbed from the soil?

• Convert them into nitrogen gas

• Use them to build plant proteins

• Store them as glucose

• Release them into the atmosphere

How do animals obtain nitrogen?

• By breathing in nitrogen gas

• By drinking water

• By feeding on plants

• By absorbing it through their skin

What happens to nitrogen when animals digest plant proteins?

• It is converted into carbon dioxide

• It is used to build animal proteins

• It is released as nitrogen gas

• It is stored as fat

Which of the following is a method of nitrogen fixation used in agriculture?

• Crop rotation

• Chemical fertilisers

• Irrigation

• Pesticides

What is the primary function of nitrates in plants?

• To provide energy

• To build proteins

• To store water

• To absorb sunlight

Which of the following is NOT a part of the nitrogen cycle?

• Nitrogen fixation

• Photosynthesis

• Ammonification

• Nitrification