Ecosystems 14

Year 10 Topic 2 – Learning Opportunity 14: Nitrogen Cycle.
This learning opportunity has 6 tasks to complete.
Target time: 50 minutes.

By the end of this learning opportunity you will be able to: explain how nitrates are made available for plant uptake, including the use of fertilisers, crop rotation and the role of bacteria in the nitrogen cycle.

Key words: nitrates, nitrogen cycle, nitrogen-fixing, root nodule, bacteria, decomposition, protein, urea, excretion, nitrifying bacteria, absorption, crop rotation, fertiliser.

Task 1: Use ‘look, cover, write, check’ to memorise this diagram of the nitrogen cycle.

Task 2: Match the name of the bacteria involved in the nitrogen cycle to its role. Watch the video and use the diagram to help you.

Find the answers at the end of the blog.

Task 3: Write 3 bullet points explaining how bacteria keep soil fertile.

Plants need nitrogen for making proteins but they can only take it in in the form of compounds such as nitrates.
Decomposers…
Nitrifying bacteria…
Nitrogen-fixing bacteria…

Find the answers at the end of the blog.

Task 4: Answer the questions about techniques farmers use to improve the growth of plants.

  1. How is crop rotation used?
  2. What other technique can farmers use? 

Find the answers at the end of the blog.

Task 2: Answers
Task 3: Answers

• Decomposers release ammonia from proteins in dead bodies and urea.
• Nitrifying bacteria in the soil then make nitrates which plants can absorb from the ammonia.
• Also, nitrogen-fixing bacteria (found in root nodules of some plants or in soil) convert nitrogen gas from the air into nitrates which plants can use.

Task 4: Answers
  1. Crop rotation involves growing different crops each year on a rotation. The first year the crop will grow and be harvested, removing nitrates from the soil. The next year a plant with nitrogen-fixing bacteria in their roots such as clover is planted. It is not harvested but ploughed back into the soil, to add nitrates.
  2. Use artificial fertilisers.

Task 5: Complete the quiz using the link below.

Quiz

You may need to refer to this diagram if it is not show within the quiz.

Challenge Task: Complete the exam question.

Challenge Task: Answers

End of Learning Opportunity 14