An astrobiologist designs an experimental sealed chamber, a "Biopod", intended to support life on a Mars research station by establishing a self-sustaining miniature aquatic ecosystem containing algae (producers), aquatic snails (consumers), and a specialized sediment layer.
The following pathways describe the movement of carbon within the Biopod ecosystem:
Match each Pathway A–D to its correct process from the list below:
The astrobiologist initially fills the sediment layer with synthetic sand containing essential mineral ions but no active bacteria or fungi.
Over a long duration, algal growth stalls because mineral ions (such as nitrates and phosphates) in the water and sediment are completely exhausted. Explain why these mineral nutrients are not recycled in this initial setup.
The astrobiologist then inoculates the sediment with active decomposer microbes. Despite the Biopod remaining completely hermetically sealed, both the algae and the microbes are able to survive long-term because they supply each other with vital gases. Explain how this gas exchange is maintained between the algae and the microbes.
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.