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CAIE IGCSE Biology 20.3 Pollution Questions

Practise pollution questions by interpreting sewage and fertiliser effects, tracing plastic hazards and explaining greenhouse gases or eutrophication.

Syllabus
2026–2028
Course
Biology 0610

Exam points

  • interpret sewage or fertiliser evidence using nitrate, bacteria, oxygen and aquatic-organism data
  • explain non-biodegradable plastic harm through entanglement, blockage and food-chain accumulation
  • identify methane and carbon dioxide sources and explain how greenhouse gases absorb outgoing heat
  • link increased methane and carbon dioxide to the enhanced greenhouse effect and climate change
  • sequence eutrophication from nitrate enrichment and producer growth through decomposition and oxygen depletion to organism death

Covered syllabus points

20.3.1—Effects of untreated sewage and excess20.3.2—Effects of non-biodegradable plastics20.3.3—Sources and effects of pollution20.3.4—Process of eutrophication of water

Question 1

[Maximum number: 1]

The bloodworm is an organism that is found in heavily polluted water.
The diagram shows where raw sewage flows into a river.

Where would there be fewest bloodworms?

Figure for Question 1 — CAIE IGCSE Biology

Question 2

[Maximum number: 6]

Large quantities of plastic waste are polluting the oceans.

Question (a)

(a)

The green turtle, Chelonia mydas, is a species of marine animal that is harmed by plastic waste.

Fig. 2.2 shows a green turtle swimming past a plastic bag in the Pacific Ocean.

Fig. 2.2

Fig. 2.2

[ 6 ]

Question (i)

(i)

Outline the dangers of non-biodegradable plastic waste to marine animals, such as green turtles.

[ 4 ]

Question (ii)

(ii)

Suggest ways to reduce the quantity of plastic waste.

[ 2 ]

Question 3

[Maximum number: 3]

Fig. 6.1 shows part of the carbon cycle in the ocean.

Fig. 6.1 (not to scale)

Fig. 6.1 (not to scale)

Describe the effect on the environment of additional carbon dioxide in the atmosphere.

Question 4

[Maximum number: 4]

Researchers investigated the effect of adding cattle manure (cattle faeces) to fields where snap bean plants, Phaseolus vulgaris, were grown. Cattle manure contains some protein.

Snap bean plants are legumes which have root nodules that contain nitrogen-fixing bacteria.

Fig. 4.1 shows some root nodules.

Fig. 4.1

Fig. 4.1

When large quantities of manure are put on fields it can lead to eutrophication of streams and rivers. This can lead to the death of fish.

Describe how eutrophication of streams and rivers can lead to the death of fish.

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