Question 1

The concentration of oxygen in the water at site A is much lower than at site B.
- Sludge worms live in places which have a low concentration of oxygen.
- Mayfly nymphs need a high concentration of oxygen.
Give evidence from Table 2 for the difference in oxygen concentration at sites A and B. Refer to sludge worms and to mayfly nymphs in your answer.

Accepted Answer

1. Look at the information given about sludge worms (live in low oxygen). Find their numbers at Site A and Site B from Table 2. Explain what these numbers suggest about the oxygen level at each site.
2. Look at the information given about mayfly nymphs (need high oxygen). Find their numbers at Site A and Site B from Table 2. Explain what these numbers suggest about the oxygen level at each site.
3. Combine these two pieces of evidence to form a conclusion about the difference in oxygen concentration.

Question 2

What mistakes do candidates make on this AQA GCSE question?

Accepted Answer

✗ Only referring to one of the two species. The question asks for reference to both.
✗ Stating the numbers from the table without explaining what they mean in terms of oxygen levels.
✗ Confusing which species indicates high/low oxygen.

How to approach this question

Full Answer

Common mistakes

Practice the full AQA GCSE Biology Foundation Tier Paper 2

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