A student measures changes in the dry mass of dead leaves over 10 days. Each sample begins with a dry mass of 80 g .
Samples contain either living microorganisms or microorganisms that have been killed. All other conditions are controlled.
| Temperature / ∘C^{\circ}\mathrm{C}∘C | Final dry mass with living microorganisms / g | Final dry mass with killed microorganisms / g |
|---|---|---|
| 20 | 70 | 78 |
| 40 | 60 | 78 |
Assume the loss with killed microorganisms represents the non-biological loss at that temperature.
After correcting for non-biological loss, how many times greater is the mean rate of decay at 40∘C40^{\circ}\mathrm{C}40∘C than at 20∘C20^{\circ}\mathrm{C}20∘C ?
2.25 times
2.00 times
1.80 times
1.25 times
40 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.