Nitrogen Cycle Worksheets

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🔬 Part 1: Nitrogen Cycle Diagram

1. Complete the nitrogen cycle diagram by filling in the missing labels. Use the word bank below to help you.

Word Bank: nitrogen gas (N₂), nitrates, nitrogen-fixing bacteria, nitrifying bacteria, denitrifying bacteria, plant roots, decomposers

2. Match each process to its correct description:

Nitrogen fixation

Nitrification

Assimilation

Ammonification

Denitrification

Converting nitrogen gas into ammonia

Plants absorbing nitrates through their roots

Converting ammonia into nitrites and nitrates

Converting nitrates back to nitrogen gas

Decomposing organic matter to release ammonia

3. Name the type of bacteria responsible for each process:

a) Nitrogen fixation: _________________________

b) Nitrification: _________________________

c) Denitrification: _________________________

📝 Part 2: Gap-Fill Paragraph

4. Complete the paragraph about the nitrogen cycle by filling in the missing words. Use the word bank to help you.

Word Bank: atmosphere, bacteria, nitrates, ammonia, plants, decomposers, nitrogen gas, roots

The nitrogen cycle begins when _____________ in the soil convert nitrogen gas from the _____________ into _____________. This process is called nitrogen fixation. The ammonia is then converted by nitrifying _____________ into _____________, which can be absorbed by _____________ through their _____________. When organisms die, _____________ break down the organic matter and release nitrogen compounds back into the soil. Finally, denitrifying bacteria convert nitrates back to _____________, returning it to the atmosphere.

5. Explain why the nitrogen cycle is important for ecosystems. Use the sentence starter below:

Sentence starter: The nitrogen cycle is important because...

6. Give two examples of how human activities can affect the nitrogen cycle:

a) _________________________________________________

b) _________________________________________________

7. Which of the following statements about the nitrogen cycle are correct? Tick all that apply:

Plants can absorb nitrogen gas directly from the atmosphere

Bacteria play a crucial role in converting nitrogen compounds

Nitrates are the form of nitrogen that plants can easily absorb

Denitrification removes nitrogen from the soil permanently

Lightning can naturally fix nitrogen in the atmosphere

💡 Part 3: Application Questions

8. A farmer notices that his crops are growing poorly despite adequate water and sunlight. Suggest how the nitrogen cycle might be involved and what the farmer could do to help:

9. Explain what would happen to an ecosystem if all the nitrogen-fixing bacteria suddenly disappeared:

10. Put the following stages of the nitrogen cycle in the correct order by numbering them 1-5:

_____ Denitrification returns nitrogen gas to the atmosphere

_____ Plants absorb nitrates through their roots

_____ Nitrogen-fixing bacteria convert nitrogen gas to ammonia

_____ Decomposers break down dead organisms releasing ammonia

_____ Nitrifying bacteria convert ammonia to nitrates