AQA · Biology · 8461
GCSE Biology: Decomposition
Ecology · AQA GCSE Biology (8461), specification point 4.7.2.3. Cards are generated from the exam board's own specification for "Decomposition", and every card links back to the page it came from. Separate science only. Specification © AQA — used with attribution.
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Name three factors that affect the rate of decay of biological material.
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Temperature, water (moisture) and availability of oxygen.
How does a warmer temperature (up to the optimum) affect the rate of decay?
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It increases the rate, because the enzymes in decomposing microorganisms work faster; above the optimum, enzymes denature and decay slows.
Why does a good oxygen supply speed up the decay of biological material?
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Decomposing microorganisms respire aerobically, so more oxygen lets them grow and break down material faster.
Why do gardeners and farmers provide optimum conditions for the decay of waste biological material?
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To produce compost quickly, which is used as a natural fertiliser for garden plants or crops.
Anaerobic decay of biological material produces ? gas.
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methane
What is a biogas generator used for?
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Producing methane gas (by anaerobic decay of biological material) for use as a fuel.
What is compost?
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Decayed waste biological material, used as a natural fertiliser for growing plants or crops.
What does AQA Biology required practical 10 investigate?
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The effect of temperature on the rate of decay of fresh milk, measured by pH change.
Why does the pH of milk fall as it decays?
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Bacteria break down the lactose in the milk into lactic acid, making it more acidic.
Why does biological material decay more slowly when it is dry?
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Decomposing microorganisms need water for growth and for their reactions, so lack of moisture slows them down.
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