Question 1 Medium
What process do plant roots use to take nitrates in?
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Answer: active transport
- Nitrates are at a lower concentration in soil water than in the root.
- So the plant uses active transport.
Parasites, mutualism and the nitrogen cycle: GCSE Combined Science Biology practice questions
A second set of questions on parasites, mutualism and the nitrogen cycle. They are different from the ones on the topic page. Try each, then open the answer and compare your working.
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Question 2 Medium
Name one sign that a plant has too little nitrate.
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Answer: yellow leaves
- Nitrates are needed to make proteins.
- Without them growth is stunted or the leaves turn yellow.
Question 3 Hard
Which group of organisms break down dead plants and release ammonium compounds into the soil?
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Answer: decomposers
- Dead organisms and waste are broken down.
- Decomposers do this.
Question 4 Hard
Name the bacteria that change ammonium compounds into nitrates.
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Answer: nitrifying bacteria
- They make nitrates available.
- They are nitrifying bacteria.
Question 5 Hard
Name the bacteria that change nitrates into nitrogen gas.
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Answer: denitrifying bacteria
- They remove nitrates from the soil.
- They are denitrifying bacteria.
Question 6 Hard
Why does a farmer grow clover in a crop rotation?
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Answer: to add nitrates to the soil
- Clover is a legume.
- Its bacteria add nitrates to the soil.
Question 7 Hard
Name the problem caused when too much fertiliser washes into a river and algae grow too quickly.
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Answer: eutrophication
- Excess nutrients make algae bloom.
- The problem is eutrophication.
Question 8 Hard
In waterlogged soil, which bacteria turn nitrates back into nitrogen gas?
Show answer
Answer: denitrifying bacteria
- They are more active where there is little oxygen.
- They are denitrifying bacteria.
Quick checks
Short questions with options. Choose one before you open the answer.
Check 1
What does interdependence mean?
Show answer
Species in a community depend on each other.
Check 2
What is a parasite?
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An organism that lives on or in a host and takes food from it, harming the host.
Check 3
Give two examples of parasites.
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Fleas, tapeworms, mistletoe, the malaria parasite.
Check 4
What is mutualism?
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A relationship where both organisms benefit.
Check 5
Give two examples of mutualism.
Show answer
Bees and flowers; nitrogen-fixing bacteria in legume root nodules; clownfish and sea anemones.
Check 6
Who benefits in parasitism?
Show answer
The parasite. The host is harmed.
Check 7
Why do plants need nitrates?
Show answer
To make amino acids and proteins.
Check 8
How do plants take in nitrates?
Show answer
By active transport through the root hairs.
Check 9
Can plants use nitrogen gas?
Show answer
No. They need nitrates.
Check 10
What percentage of the air is nitrogen?
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About 78%.
Check 11
What do nitrogen-fixing bacteria do?
Show answer
Change nitrogen gas into nitrates (nitrogen compounds) that plants can use.
Check 12
Where do nitrogen-fixing bacteria live?
Show answer
In the soil and in nodules on the roots of legumes.
Check 13
Give three examples of legumes.
Show answer
Clover, peas and beans.
Check 14
What do decomposers do in the nitrogen cycle?
Show answer
Break down dead matter and waste and release ammonium compounds.
Check 15
What do nitrifying bacteria do? (Higher tier)
Show answer
Change ammonium compounds into nitrates.
Check 16
What do denitrifying bacteria do? (Higher tier)
Show answer
Change nitrates into nitrogen gas.
Check 17
Where are denitrifying bacteria most active?
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In waterlogged soil.
Check 18
What natural event also fixes a little nitrogen?
Show answer
Lightning.
Check 19
What is crop rotation?
Show answer
Growing a different crop on a field each year, including a legume.
Check 20
Why does crop rotation help the soil?
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The legume's bacteria add nitrates, and pests of one crop do not build up.
Check 21
What do fertilisers contain?
Show answer
Nitrates, phosphates and potassium compounds.
Check 22
What is the problem with too much fertiliser?
Show answer
It can wash into rivers and cause eutrophication.
Check 23
What are the signs of nitrate deficiency in plants?
Show answer
Stunted growth and yellow older leaves.
Check 24
How do animals get their nitrogen?
Show answer
By eating plants or other animals.
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