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NEET-UG Biology · Class 12

Productivity: GPP, NPP and their numbers — NEET & JEE Questions

Productivity: GPP, NPP and their numbers is a topic in Ecosystem, a Class 12 Biology chapter of the NEET-UG syllabus. TestBudy holds 13 published NEET-UG questions on Productivity: GPP, NPP and their numbers, each with the marking scheme of the real paper. The ideas it examines include How GPP, respiration and NPP relate, Secondary productivity versus net primary productivity, Global and ocean productivity figures.

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Key formulas and concepts

The ideas Productivity: GPP, NPP and their numbers is examined on, as they are tagged in the syllabus tree.

  • How GPP, respiration and NPP relate
  • Secondary productivity versus net primary productivity
  • Global and ocean productivity figures

Productivity: GPP, NPP and their numbers MCQs with solutions

10 of the 13 published questions on this topic, exactly as they appear in a test. Answers and worked solutions come with your result rather than on this page.

  1. Question 1 · difficulty L1 · recall

    What does gross primary productivity measure?

    • A. Only the energy stored after respiration
    • B. Only the biomass consumed by herbivores
    • C. Total producer organic-matter production
    • D. The rate of decomposition

  2. Question 2 · difficulty L2 · understanding

    The rate of biomass production by consumers:

    • A. secondary productivity
    • B. mineralisation
    • C. net primary productivity
    • D. gross primary productivity

  3. Question 3 · difficulty L2 · understanding

    The relation between net and gross primary productivity:

    • A. GPP = NPP - respiration
    • B. NPP = GPP + respiration
    • C. NPP = respiration only
    • D. NPP = GPP - respiration

  4. Question 4 · difficulty L2 · understanding

    The total rate of photosynthetic production by producers:

    • A. decomposition rate
    • B. secondary productivity
    • C. net primary productivity
    • D. gross primary productivity

  5. Question 5 · difficulty L2 · understanding

    Two forests have the same GPP, but forest X has much higher producer respiration than forest Y. Which statement is correct?

    • A. NPP is unrelated to respiration
    • B. Forest X has higher NPP
    • C. Both forests must have identical NPP
    • D. Forest X has lower NPP

  6. Question 6 · difficulty L3 · application

    An ecosystem has a GPP of 2,000 units and producer respiration of 800 units over the same period. What is its NPP?

    • A. 1,200 units
    • B. 800 units
    • C. 2,800 units
    • D. 2,000 units

  7. Question 7 · difficulty L3 · application

    An ecosystem has gross primary productivity of 2400 kJ m−2^{-2} yr−1^{-1} and plant respiration of 900 kJ m−2^{-2} yr−1^{-1}. What is its net primary productivity?

    • A. 1500 kJ m−2^{-2} yr−1^{-1}
    • B. 2400 kJ m−2^{-2} yr−1^{-1}
    • C. 3300 kJ m−2^{-2} yr−1^{-1}
    • D. 900 kJ m−2^{-2} yr−1^{-1}

  8. Question 8 · difficulty L3 · application

    If GPP is 1800 g m−2^{-2} yr−1^{-1} and NPP is 1200 g m−2^{-2} yr−1^{-1}, how much biomass-equivalent energy was used in plant respiration?

    • A. 600 g m−2^{-2} yr−1^{-1}
    • B. 1200 g m−2^{-2} yr−1^{-1}
    • C. 1800 g m−2^{-2} yr−1^{-1}
    • D. 3000 g m−2^{-2} yr−1^{-1}

  9. Question 9 · difficulty L3 · application

    A grassland fixes 5000 kJ m−2^{-2} yr−1^{-1} by photosynthesis and producers use 40% of this in respiration. What is NPP?

    • A. 2000 kJ m−2^{-2} yr−1^{-1}
    • B. 3000 kJ m−2^{-2} yr−1^{-1}
    • C. 5000 kJ m−2^{-2} yr−1^{-1}
    • D. 7000 kJ m−2^{-2} yr−1^{-1}

  10. Question 10 · difficulty L4 · application

    Which quantity represents the biomass or energy available to herbivores from producers over a given period?

    • A. Net primary productivity
    • B. Gross primary productivity before plant respiration
    • C. Plant respiration alone
    • D. Standing crop only

Common mistakes in Productivity: GPP, NPP and their numbers

Recorded against questions in this topic that are not shown above, so none of these points at an answer you can see on this page.

  • Assumes equal GPP guarantees equal NPP.
  • Subtracts respiration from NPP instead of adding it back to recover GPP.
  • Compares GPP values alone and ignores different respiration costs.

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