Two lifeguards, A and B, each tow the same training dummy for two minutes at the same constant speed.
The table shows the extra volume of oxygen each lifeguard took in above their resting requirement during each minute of recovery.
| Recovery interval after the tow in minutes | Extra oxygen taken in by lifeguard A in dm³ | Extra oxygen taken in by lifeguard B in dm³ |
|---|---|---|
| 0–1 | 2.4 | 3.0 |
| 1–2 | 1.6 | 2.2 |
| 2–3 | 0.8 | 1.4 |
| 3–4 | 0.2 | 0.6 |
Immediately after the final interval, the oxygen uptake of both lifeguards had returned to the resting level.
Calculate how much greater lifeguard B's oxygen debt was than lifeguard A's.
Give your answer in dm³.
Explain what the difference in oxygen debt suggests about respiration in lifeguard B's muscles during the tow.
A student concludes that lifeguard B's oxygen debt had been fully repaid by the end of the second minute of recovery.
Suggest why this conclusion is not supported by the data.
92 exam-style questions on AQA GCSE Biology 4.2 Respiration, covering 4.2.1 Aerobic and anaerobic respiration, 4.2.2 Response to exercise, and 4.2.3 Metabolism. Each one has a worked solution and a mark scheme showing where the marks go.