2. Ecosystems as a System Aims To understand that ecosystems operate as a system. To learn what the inputs, processes and outputs of ecosystems are.

4. Inputs, Processes and Outputs in Ecosystems The ecosystem is our environment, our surroundings. In an ecosystem, materials are exchanged from one part to other parts e.g. vegetation needs water, carbon dioxide and nutrients from parts of its ecosystem. In exchange, the vegetation enriches the soil when it dies and decomposes. An ecosystem may be very large, such as a tropical rainforest, or very small, such as a single oak tree, but all ecosystems have their own systems of exchange and their own special environments.

5. All ecosystems have: Inputs – Things entering it – eg sunlight, rainfall Processes – Things operating within it – photosynthesis, weathering of rock into soil, decomposition Outputs – Things leaving it – the scenery/landscape, evaporation

6. People can also damage and pollute the ecosystem through their activities e.g. Oil spills at sea. Warm water from power stations being put back into rivers. Deforestation. Air pollution from factories.

7. Activity: An Oak Tree Ecosystem KEY Inputs Processes Outputs TASK: Label the inputs, processes and outputs then colour code them using the key below

8. The Balancing Act Ecosystems are delicately balanced but they can change over time. This may be because new plants arrive, the climate changes or because of human activity. In most of the populated areas of the world, the natural vegetation has been cleared, often by fire. When trees are cut down or grasses are ploughed up for agriculture, the natural ecosystem is destroyed. The nutrients that went into the soil from dead leaves or roots no longer exist and have to be replaced by fertiliser or manure. The protection given by continuous plant cover from wind and rain no longer exists, so erosion becomes a problem. As plants are cleared and animals are killed, food chains are disrupted.