AQA GCSE Combined Science: Trilogy Biology Paper 2 (Foundation), 2022: Question 6
6 marks · Standard Demand difficulty · Extended Answer
Explain how human activities are polluting rivers, lakes and seas.
Practise this questionQuestion
Question text
06 Water pollution is a problem for humans and wildlife.
Explain how human activities are polluting rivers, lakes and seas.
[6 marks]
Mark scheme
Show the mark scheme
Question 6
AO /
Question Answers Mark
Spec. Ref.
06 Level 3: Relevant points (reasons/causes) are identified, given in 5–6 AO3
detail and logically linked to form a clear account.
Level 2: Relevant points (reasons/causes) are identified, and there 3–4 AO3
are attempts at logical linking. The resulting account is not fully AO1
clear.
Level 1: Points are identified and stated simply, but their relevance 1–2 AO1
is not clear and there is no attempt at logical linking.–OMBINED SCIENCE: TRILOGY – –
No relevant content 0
06 Indicative content 4.7.3.2
cont. Increase in world population 4.7.2.1
• sewage (released into rivers / lakes / seas)
o causes algae to grow
o algae block light
o causing plants to die and decompose
o leading to lack of oxygen in the water
o (sewage) could contain pathogens
Need to produce more food for world’s population
• fertilisers (used on farms to increase crop yield, leach into rivers
/ lakes / seas)
o causes algae to grow
o leading to lack of oxygen in the water
• herbicides / pesticides (used on farms to increase crop yield,
run into rivers / lakes / seas)
o build-up in food chains
Increasing demand for products / energy
• toxic chemicals or named toxic chemicals (run into rivers / lakes
/ seas)
o from factories / industry or power stations
o build-up in food chains
o chemicals may cause mutations or chemicals may act
as hormones
o radiation leaks from nuclear (power stations)
o (oil) spills from extraction / rigs / tankers in oceans
o acid rain formation
o acidification of lakes
o increased carbon dioxide emissions causes acidification
of oceans
Buildup of waste products
• litter / plastics (thrown in rivers / lakes / seas) 21
o example of effect on living organisms, such as plastics
consumed or plastics build up in stomach or plastics get
stuck around beaks
o (most) plastics are not biodegradable
o build-up of microplastics in water animals
Consequence of the above is that organisms living in rivers / lakes /
seas are harmed / die
For Level 3 students need to consider different types of pollution
Total Question 6 6
How to answer it
Human Impact: Water Pollution
What this question tests
This 6-mark extended response assesses your ability to identify different sources of water pollution (sewage, farming, industry, and waste) and explain the biological consequences of each. It requires you to link human activities to specific environmental impacts like eutrophication and bioaccumulation.
Explaining Water Pollution
This is a "Level of Response" question. To get the full 6 marks, you cannot just list facts; you must group your ideas and link the cause to the effect logically.
💡 Key Knowledge: Eutrophication
- Sources: Sewage and Fertilisers (leaching from farms).
- Process: These contain nitrates/phosphates which cause algae to grow rapidly (algal bloom).
- Effect: Algae block light → plants underneath die → bacteria decompose dead plants → bacteria use up Oxygen for respiration → fish die.
💡 Key Knowledge: Toxic Chemicals
- Sources: Pesticides/Herbicides from farms or heavy metals from factories.
- Bioaccumulation: These chemicals do not break down. They build up in the bodies of organisms and increase in concentration as they move up the food chain.
How to Structure Your Answer
🧠 Exam Technique: The "Level 3" Secret
Examiners look for breadth and depth. To reach 5-6 marks:
- Mention at least three different types of pollution (e.g., Sewage, Chemicals, and Plastic).
- Use "linking words" like "which leads to..." or "resulting in..." to show cause and effect.
- Mention the growing human population as the root cause for the increased demand for food and energy.
✅ Model Answer Points
- Sewage: Released into rivers; contains pathogens and causes algae growth which depletes oxygen.
- Farming: Fertilisers leach into water causing eutrophication; Pesticides build up in food chains.
- Industry: Toxic chemicals or oil spills from tankers harm marine life.
- Waste: Plastics are non-biodegradable; they are eaten by animals or trap them.
❌ Common Errors
- Confusing Pollutants: Don't say "CO₂ causes water pollution" unless you specifically mention ocean acidification.
- Vague Statements: Avoid saying "it kills fish" without explaining why (e.g., lack of oxygen or toxic buildup).
- Mixing up Air/Water: Don't talk about global warming or the ozone layer here!
Specific Impacts to Include
📐 Step-by-Step: The Plastic Problem
- Humans throw litter/plastics into drains or oceans.
- Most plastics are not biodegradable (they don't rot).
- Large pieces are consumed by animals, filling their stomachs so they cannot eat real food.
- Plastics break down into microplastics, which enter the food chain and can be toxic.
Visualising the Process
If you were to draw a diagram of eutrophication for revision, it should show:
- A farm next to a river with arrows showing fertilisers washing in.
- A thick green layer of algae at the surface.
- Dead plants at the bottom with "X" marks.
- Bacteria (represented by dots) surrounding the dead plants.
- A label saying "Low O₂" and dead fish floating.
Topics
Biology · B7: Ecology
Question and mark scheme from the AQA GCSE Combined Science: Trilogy examination, Biology Paper 2 (Foundation), 2022. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.