Acid rain is formed when sulfur dioxide and nitrogen oxides are released into the atmosphere. Explain how acid rain affects living organisms and ecosystems.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Power stations burning fossil fuels and vehicle exhausts are major sources of sulfur dioxide and nitrogen oxides. These gases dissolve in water droplets in clouds, forming acids that fall as acid rain, sometimes hundreds of kilometres from the original source.
Model answer (5 marks)
Acid rain lowers the pH of lakes and rivers, making the water more acidic.
The lower pH is harmful to aquatic life – fish and invertebrates cannot survive in acidic water, leading to their death.
It also damages vegetation; the acids damage leaves and can leach nutrients from the roots, killing or weakening trees.
In the soil, acid rain leaches minerals and nutrients, reducing soil fertility and making it harder for plants to grow.
The loss of plants and aquatic organisms reduces biodiversity, and the disappearance of one species can upset the food chain and food web.
The lower pH is harmful to aquatic life – fish and invertebrates cannot survive in acidic water, leading to their death.
It also damages vegetation; the acids damage leaves and can leach nutrients from the roots, killing or weakening trees.
In the soil, acid rain leaches minerals and nutrients, reducing soil fertility and making it harder for plants to grow.
The loss of plants and aquatic organisms reduces biodiversity, and the disappearance of one species can upset the food chain and food web.
Examiner tips
- Use the exact terms from the mark scheme – ‘low pH’, ‘aquatic organisms’, ‘vegetation’, ‘soil fertility’, ‘biodiversity’. Include the causal chain: acid rain → lower pH → organism death → ecosystem impact. Keep each point brief but complete – one sentence per point.
- common_mistakes
- :
- Writing ‘acid rain kills fish’ without mentioning the pH change. Using vague terms like ‘damage to plants’ instead of specifying leaf/root damage. Omitting the link between soil leaching and reduced biodiversity.
Mark scheme (5 marks)
- Acid rain lowers the pH of lakes and rivers / makes water more acidic
- Low pH kills aquatic organisms / fish and invertebrates cannot survive in acidic water
- Acid rain damages or kills trees / vegetation by damaging leaves or roots
- Acid rain leaches / washes away minerals/nutrients from soil, reducing soil fertility
- Loss of one species affects others in the food chain / food web, reducing biodiversity
Key terms in this question
Related
- All Eduqas A-Level Biology revision notes →
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- Decode the mark scheme abbreviations →
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