Pollution Cambridge IGCSE Biology (9–1) revision
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In plain words
What we throw away doesn't disappear. Fertiliser washed off fields turns rivers green and suffocates fish. Gases from engines and cattle wrap the planet in an extra blanket. Plastic outlasts everyone alive today.
Three things to know
- Greenhouse gases such as carbon dioxide and methane trap heat in the atmosphere. More of them means an enhanced greenhouse effect, global warming and climate change.
- Eutrophication: fertiliser or sewage gets into water → algae and water plants grow fast → they block the light and die → decomposers break them down, respiring and using up the oxygen → fish and other animals die for lack of oxygen.
- Plastics that don't break down harm animals that swallow them or get tangled in them, on land and in water.
Tips and tricks
- Eutrophication is a chain. Give the steps in order and finish with "the decomposers use up the dissolved oxygen".
- The fish don't die from the fertiliser itself. They die from lack of oxygen.
It lands in your notebook with its questions as flashcards.
Pollution: 5 questions and answers
These are the quiz’s questions. Do the quiz first, then come back here for the ones that got you.
Which is a greenhouse gas?
Carbon dioxide and methane both trap heat.
What starts eutrophication?
The extra nutrients make algae grow.
In eutrophication, what uses up the oxygen in the water?
They respire aerobically as they work.
What is the effect of more greenhouse gases in the atmosphere?
More heat is trapped.
Why are some plastics a long-term problem?
They are non-biodegradable.
Quiz
5 questions
Tap an answer and you’ll see straight away whether it’s right, and why.
Worksheet
3 questions, 9 marks. Write your answers on paper, then check them.
Pollution
Cambridge IGCSE Biology (9–1) 0970 · 9 marks · papermunch.org
Name ______________________________ Date ______________
Name two greenhouse gases and state the effect of an increase in their concentration.[2]
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Carbon dioxide and methane. An enhanced greenhouse effect, leading to global warming (climate change).
Describe how fertiliser washed into a lake can cause the death of fish.[5]
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The nitrates make algae and water plants grow rapidly. They block light from the plants below, which die. Decomposers (bacteria) break down the dead plants. The decomposers respire aerobically and use up the dissolved oxygen. Fish die from lack of oxygen.
Explain why non-biodegradable plastics are harmful to wildlife.[2]
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They are not broken down, so they build up. Animals swallow them or become tangled in them and are injured or killed.
Answers: Pollution
- 1. Carbon dioxide and methane. An enhanced greenhouse effect, leading to global warming (climate change).
- 2. The nitrates make algae and water plants grow rapidly. They block light from the plants below, which die. Decomposers (bacteria) break down the dead plants. The decomposers respire aerobically and use up the dissolved oxygen. Fish die from lack of oxygen.
- 3. They are not broken down, so they build up. Animals swallow them or become tangled in them and are injured or killed.