Water and carbon cycles as natural systems — AQA A-Level Geography
Test yourself on Water and carbon cycles as natural systems with AQA A-Level practice questions.
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Water and carbon cycles as natural systems explained
Physical systems comprise interrelated components working together.
Read the full explanation
At the global scale, the water and carbon cycles are closed systems for matter: water and carbon circulate within the Earth system while energy crosses its boundary. At local scales, such as a drainage basin, they operate as open systems with inputs (precipitation) and outputs (runoff) crossing the boundary. Matter is held in stores or components (oceans, forests) and moves via flows or transfers (infiltration, photosynthesis). When inputs equal outputs, systems achieve dynamic equilibrium. Positive feedback amplifies change, whereas negative feedback dampens change and helps restore equilibrium.
Your focus
- Define key systems concepts including inputs, outputs, stores, and flows.
- Apply the concepts of positive and negative feedback to the water and carbon cycles.
- Explain how dynamic equilibrium is maintained within physical systems.
Water and carbon cycles as natural systems exam tips
Marking Points
- Define a system as a set of interrelated components comprising stores, flows, inputs, and outputs.
- Explain that the global water and carbon cycles are closed systems where only energy crosses the boundary, but at a local scale they operate as open systems.
- Identify solar radiation as a primary energy source for both cycles, gravity as a driver mainly for water transfers, and geothermal energy driving the geological carbon cycle.
- Distinguish between positive feedback, which exacerbates changes to a system, and negative feedback, which neutralises changes to restore dynamic equilibrium.
Examiner Tips
- 💡Always link systems terminology directly to specific examples from either the water or carbon cycle to demonstrate applied understanding.
- 💡When discussing dynamic equilibrium, emphasise that the system is not static but is constantly adjusting to maintain a balance between inputs and outputs.
- 💡Use annotated flow diagrams in your exam answers to clearly illustrate feedback loops and system components.
Common Mistakes
- Confusing positive and negative feedback; correction: remember that positive feedback amplifies a change away from equilibrium, while negative feedback reduces the effect of the change.
- Describing the global water cycle as an open system; correction: state that the global cycle is a closed system because only energy, not matter, crosses its boundary.
- Using 'store' and 'flow' interchangeably; correction: clearly distinguish stores as places where matter is held (e.g. oceans) and flows as the movement between them (e.g. evaporation).