Lesson 3.5.3.1

3.5.3.1 Biomass and net primary productivity Quiz: AQA Biology, Unit 5

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 3.5.3.1, Biomass and net primary productivity: 20 multiple choice questions for the AQA Biology (7402), Unit 5: Energy transfers in and between organisms, written with Revision Ninja.

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The 20 questions

  1. What term describes the total chemical energy stored in plant biomass per area?

    • Net primary production
    • Secondary production
    • Respiratory loss
    • Gross primary production

  2. Which equation correctly defines net primary production (NPP)?

    • NPP = R - GPP
    • NPP = GPP + R
    • NPP = GPP - R
    • NPP = GPP / R

  3. Biomass can be measured as dry mass of tissue or mass of which element?

    • Carbon
    • Oxygen
    • Nitrogen
    • Phosphorus

  4. What parameter of dry biomass is estimated using bomb calorimetry?

    • Water mass
    • Rate of respiration
    • Total carbon mass
    • Chemical energy store

  5. Which of the following is a correct unit for primary productivity?

    • g m^-2
    • kJ ha^-1
    • kJ year^-1
    • kJ ha^-1 year^-1

  6. What is the main use of sugars synthesised by plants?

    • Cellulose walls
    • Storage starch
    • Active transport
    • Respiratory substrates

  7. What formula correctly defines net primary production (NPP)?

    • R minus GPP
    • GPP plus R
    • GPP divided by R
    • GPP minus R

  8. A plant has GPP of 5000 kJ and respiratory losses of 1800 kJ. What is its NPP?

    • 1800 kJ
    • 3200 kJ
    • 2778 kJ
    • 6800 kJ

  9. If GPP is 8400 and NPP is 5100, what are the respiratory losses?

    • 3300 kJ m^-2
    • 13500 kJ m^-2 yr^-1
    • 3300 kJ m^-2 yr^-1
    • 5100 kJ m^-2 yr^-1

  10. If GPP is 2500 and respiratory losses are 40%, what is NPP?

    • 1000 kJ m^-2 yr^-1
    • 1500 kJ m^-2 yr^-1
    • 3500 kJ m^-2 yr^-1
    • 2000 kJ m^-2 yr^-1

  11. A 0.5 g sample of dry plant biomass releases 10 kJ when burnt in a calorimeter. How much energy is stored per kilogram of dry biomass?

    • 200 kJ
    • 20 000 kJ
    • 20 kJ
    • 5 kJ

  12. Why is dry mass measured instead of wet mass when calculating biomass?

    • Minerals are lost
    • Water content varies
    • Carbon is volatile
    • Proteins break down

  13. Which process accounts for the difference between GPP and NPP?

    • Transpiration
    • Respiration
    • Egestion
    • Photosynthesis

  14. Which ecosystem has higher NPP: a forest (GPP 20 000, R 12 000) or grassland (GPP 8000, R 3000)?

    • Grassland
    • Forest
    • Neither
    • Both equal

  15. If a crop has a GPP of 25 000 kJ ha⁻¹ yr⁻¹ and respiratory losses are 60%, what is NPP?

    • 40 000 kJ ha⁻¹ yr⁻¹
    • 5 000 kJ ha⁻¹ yr⁻¹
    • 15 000 kJ ha⁻¹ yr⁻¹
    • 10 000 kJ ha⁻¹ yr⁻¹

  16. Two plots have identical GPP, but plot P has higher respiratory losses. Plot P will have:

    • Higher NPP
    • Equal NPP
    • Lower NPP
    • Zero GPP

  17. Which change decreases net primary productivity without altering gross primary productivity?

    • Decreased temperature
    • Increased light intensity
    • Decreased respiration
    • Increased respiration

  18. The GPP of a grassland is 9000 kJ per square metre per year and NPP is 3600 kJ per square metre per year. What fraction of GPP is lost to respiration?

    • 40%
    • 25%
    • 75%
    • 60%

  19. Why is gross primary productivity not entirely available for plant growth?

    • Absorbed by soil
    • Lost in faeces
    • Reflected as light
    • Used in respiration

  20. A plant has GPP of 4000 kJ per square metre per year and NPP of 2500 kJ per square metre per year. What percentage of GPP is lost to respiration?

    • 15%
    • 62.5%
    • 25%
    • 37.5%

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