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Cycling materials

5 lessons in Ecology.

26 exam questions · 55 marks

7.6 The carbon cycle How carbon is cycled between the air, plants, animals, decomposers and fossil fuels by photosynthesis, feeding, respiration, decay and combustion, and why decomposers matter. AQA Edexcel OCR 7.7 The water cycle How water is cycled by evaporation, transpiration, condensation and precipitation, why the water cycle provides fresh water for plants and animals on land, and (Edexcel) how potable water is obtained, including by desalination. AQA Edexcel OCR 7.8 The nitrogen cycle Edexcel: how nitrogen is cycled by nitrogen-fixing, nitrifying and denitrifying bacteria and decomposers, why plants need nitrates, and how farmers use fertilisers and crop rotation with legumes to increase soil nitrates. Edexcel 7.9 Decomposition How temperature, water and oxygen affect the rate of decay by microorganisms, how gardeners make compost, how biogas is made by anaerobic decay (AQA), how food is preserved by slowing decay (Edexcel), and how to calculate the rate of decay. Separate only AQA Edexcel OCR 7.10 Required practical: temperature and the rate of decay AQA required practical 10: investigating how temperature affects the rate of decay of fresh milk by measuring the time taken for lipase to lower the pH, shown by phenolphthalein turning colourless, and calculating rate. Separate only AQA