Lesson 4.7.2.3

4.7.2.3 Decomposition (biology only) Quiz: AQA Biology, Unit 7

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 4.7.2.3, Decomposition (biology only): 20 multiple choice questions for the AQA GCSE Biology (8461), Unit 7: Ecology, written with Revision Ninja.

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The 20 questions

  1. What do gardeners produce by providing optimum decay conditions for waste material?

    • Fertiliser chemical
    • Compost
    • Cellulose
    • Biogas

  2. How is compost used by farmers and gardeners?

    • Weed killer
    • Animal feed
    • Pest control
    • Natural fertiliser

  3. Which gas does anaerobic decay produce?

    • Nitrogen
    • Methane
    • Carbon monoxide
    • Oxygen

  4. What can biogas generators produce that can be used as fuel?

    • Glucose syrup
    • Methane gas
    • Oxygen gas
    • Mycoprotein

  5. Which factor, alongside temperature and water, directly affects the rate of decay?

    • Soil pH
    • Oxygen availability
    • Light intensity
    • Carbon dioxide level

  6. Which liquid's decay is investigated in Required Practical 10 by measuring pH change?

    • Starch suspension
    • Glucose solution
    • Fresh milk
    • Egg white

  7. What change is measured to track the rate of decay in the milk practical?

    • Volume change
    • Mass loss
    • Temperature rise
    • pH change

  8. What does anaerobic mean?

    • At high temperature
    • In bright light
    • With oxygen
    • Without oxygen

  9. As temperature increases up to the optimum, what happens to the decay rate?

    • Stays constant
    • Stops completely
    • Increases
    • Decreases

  10. A waste sample loses 30 g in 6 days. What is the average rate of mass loss per day?

    • 5 g per day
    • 36 g per day
    • 180 g per day
    • 0.2 g per day

  11. A decaying material has 100 g at day 0 and 40 g at day 4. What is the average rate of mass loss?

    • 15 g per day
    • 25 g per day
    • 140 g per day
    • 60 g per day

  12. What type of decay occurs in the absence of oxygen to produce methane gas?

    • Aerobic decay
    • Combustion
    • Photosynthesis
    • Anaerobic decay

  13. Why do gardeners aerate a compost heap by regularly turning it over?

    • Remove water
    • Lower temperature
    • Provide oxygen
    • Prevent bacteria

  14. What useful gas is produced by biogas generators during anaerobic decay?

    • Carbon dioxide
    • Oxygen
    • Methane
    • Nitrogen

  15. How does increasing temperature from 5 °C to 35 °C affect the rate of decay?

    • It stays constant
    • It increases
    • It decreases
    • It stops completely

  16. Which condition speeds up the rate of decay in a compost heap?

    • Low temperature
    • Zero oxygen level
    • High carbon dioxide
    • High oxygen level

  17. A material's mass falls from 250 g to 200 g during decay. What is the percentage loss?

    • 50%
    • 80%
    • 25%
    • 20%

  18. Why does decay happen very slowly at low temperatures?

    • Lack of oxygen
    • Slow enzyme activity
    • Lack of water
    • Denatured enzymes

  19. Which environment results in the fastest rate of biological decay?

    • Cold, moist, sealed
    • Cold, dry, oxygenated
    • Warm, moist, oxygenated
    • Warm, dry, sealed

  20. What gas is produced when organic material undergoes anaerobic decay?

    • Oxygen
    • Methane
    • Nitrogen
    • Carbon dioxide

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