Topic 3 - Inter-relationships: Nitrogen Cycle

Question 1

What is the role of decomposers in the nitrogen cycle?

Answer 1

Decomposers (e.g. bacteria, fungi, worms) in the soil break down dead plants and animals. Decomposer bacteria in the soil turn proteins (from dead plants and animals) and urea (in animal waste) into ammonia.

Question 2

Where are nitrogen-fixing bacteria found?

Answer 2

In the soil and in nodules in the roots of legume plants.

Question 3

Why is nitrogen fixation important in the nitrogen cycle?

Answer 3

Nitrogen gas is very unreactive so it can’t be used directly by plants or animals. It has to be turned into nitrogen compounds, e.g. nitrates, so it can be used.

Question 4

What is the role of denitrifying bacteria in the nitrogen cycle?

Answer 4

They convert nitrates in nitrogen gas. This is released back into the atmosphere and can be used again by plants once it has been fixed.

Question 5

What do plants use nitrates for?

Answer 5

To make proteins for growth.