A timber yard processes shredded bark and wood chips in two insulated treatment drums. Each drum receives plant waste with an initial dry mass of 50.0 kg. Both drums are kept equally moist and receive the same supply of air.
After 14 days, the remaining dry mass is measured.
| Drum | Temperature (°C) | Initial dry mass (kg) | Dry mass after 14 days (kg) |
|---|---|---|---|
| A | 35 | 50.0 | 38.8 |
| B | 70 | 50.0 | 47.2 |
A sensor showed that the concentration of carbon dioxide in the air leaving drum A increased during the 14 days.
Suggest why.
Use the data to explain the difference in the rate of decay in the two drums.
The finished material can be added to one of two plots containing the same species of plant. All other conditions in the plots are the same.
| Plot | Nitrate concentration in the soil (mg per kg) |
|---|---|
| X | 4 |
| Y | 18 |
Explain which plot should receive the finished material to produce the greater increase in plant growth.
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.