A student investigates the decay of dead aquatic plant material by microorganisms.
Each sample has an initial dry mass of 10.0 g. The samples are kept moist and have free access to air. At the end of each trial, the student dries each sample before measuring its final dry mass.
| Temperature / ∘C^{\circ}\mathrm{C}∘C | Time / days | Final dry mass of sample 1 / g | Final dry mass of sample 2 / g | Final dry mass of sample 3 / g |
|---|---|---|---|---|
| 15 | 12 | 8.8 | 8.7 | 8.9 |
| 30 | 8 | 8.2 | 8.1 | 8.3 |
Calculate the percentage increase in the mean rate of decay from 15∘C15^{\circ}\mathrm{C}15∘C to 30∘C30^{\circ}\mathrm{C}30∘C.
The student predicts that the mean rate of decay at 60∘C60^{\circ}\mathrm{C}60∘C would be greater than the mean rate at 30∘C30^{\circ}\mathrm{C}30∘C.
Evaluate this prediction.
83 exam-style questions on AQA GCSE Biology 7.2 Organisation of an ecosystem, covering 7.2.1 Levels of organisation, 7.2.2 How materials are cycled, 7.2.3 Decomposition, and 7.2.4 Impact of environmental change (HT only). Each one has a worked solution and a mark scheme showing where the marks go.