Describe how the burning of fossil fuels can lead to damage to freshwater ecosystems.

WJEC GCSE Biology (Wales) — 1.6.3 Human impact on the environment · Describe · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

Burning fossil fuels releases sulphur dioxide and nitrogen oxides into the atmosphere.
These gases dissolve in rainwater or cloud droplets to form acid rain.
Acid rain falls on lakes and rivers, lowering their pH.
The lower pH is toxic to aquatic organisms, killing them and reducing biodiversity.

Examiner tips

Use the exact terms "sulphur dioxide", "nitrogen oxides", "acid rain", "lowering pH" and "reducing biodiversity". Show the causal chain: emission → dissolution → acid rain → pH drop → organism death. Keep each point brief and to the point to hit all four marks.

Common mistakes

Writing "nitrogen dioxide" instead of "nitrogen oxides". Failing to mention the pH drop or its effect on biodiversity. Using vague phrases like "pollution" without specifying acid rain.

Mark scheme (4 marks)

Burning fossil fuels releases sulfur dioxide / nitrogen oxides into the atmosphere
These gases dissolve in rainwater / clouds to form acid rain
Acid rain lowers the pH of lakes / rivers / freshwater ecosystems
Low pH is toxic to / kills aquatic organisms, reducing biodiversity

Key terms in this question

fossil fuels