A student builds a sealed, transparent glass terrarium to model a self-sustaining ecosystem.
The following pathways describe the movement of carbon within this ecosystem:
Match each Pathway 1–4 to its correct process from the list below:
The student first sets up the terrarium using sterilized soil that contains minerals but no living microorganisms.
Over time, plant growth ceases because the minerals in the soil are depleted. Explain why the minerals are not replenished in this setup.
The student then introduces beneficial microbes to the soil. Although the terrarium remains completely sealed, both the plants and the soil microbes are able to survive because they supply each other with the gases they need. Explain how this gas exchange occurs.
67 exam-style questions on OCR GCSE Biology 4.1 Ecosystems, covering 4.1.1 Cycling of materials in ecosystems, 4.1.2 Microorganisms in cycling materials, 4.1.3 The carbon and water cycles, 4.1.4 Factors affecting decomposition, 4.1.5 Levels of organisation in an ecosystem, 4.1.6 Abiotic and biotic factors affecting communities, 4.1.7 Interdependence and competition, 4.1.8 Trophic levels, 4.1.9 Pyramids of biomass, and 4.1.10 Efficiency of biomass transfers. Each one has a worked solution and a mark scheme showing where the marks go.