A biologist investigates how decomposers recycle carbon and mineral ions from dead leaves.
Dead leaves are kept in a container separated from a growing plant by a barrier. The barrier allows gases to pass through but prevents liquids, dissolved mineral ions and microorganisms from crossing. Carbon atoms in the dead leaves have a detectable label.
After several days, labelled carbon is detected in glucose in the plant's new leaves. Mineral ions released from the dead leaves remain in their container.
Which explanation accounts for both observations?
Decomposer digestion releases labelled glucose vapour for leaf uptake, while mineral ions must remain dissolved to reach roots.
Decomposer respiration releases labelled carbon dioxide for photosynthesis, while mineral ions require a liquid route to roots.
Decomposer respiration releases labelled carbon dioxide for root respiration, while mineral ions require a liquid route to roots.
Decomposer digestion releases labelled mineral ions for photosynthesis, while unlabelled mineral ions cannot cross the barrier.
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.