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Differentiate between Net… (Class 12 Biology 2025, Q18B)

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BiologyCBSE Class 12 · Board exam 2025, set 57/1/1 · 2 marks · Very short answer

CBSE Class 12 Biology 2025: question 18(B)

Set in the CBSE Class 12 board exam of 2025, paper 57/1/1, section B, question 18(B), for 2 marks. Try it first; the hints and our step-by-step solution are below.

Q18(B) · 2 marks · Very short answerEcosystem

Differentiate between Net primary productivity and Gross primary productivity in an ecosystem.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2025 board paper, set 57/1/1.

Hints

Open one hint at a time and try again before the next.

Hint 1

One of these is the total and the other is what remains after a loss.

Hint 2

Which process do plants use that consumes part of the organic matter they make?

Step-by-step solution

Each step shows the marks it earns, as an examiner would award them. Checked by an independent re-solve from the question paper.

  1. Net Primary Productivity (NPP)Gross Primary Productivity (GPP)
    GPP minus the energy lost in respiration by plants; Rate of production of organic matter by producers during photosynthesis
    Biomass actually available for consumption by heterotrophs (herbivores, decomposers)Part of it is used up by the plants themselves in respiration, so it is not all available to consumers
    2 marks

Answer: GPP is the total rate of organic matter production in photosynthesis; NPP = GPP − respiration loss, the biomass available to heterotrophs.

Where the marks are

  • Definition of NPP as GPP − R (½ mark)
  • Definition of GPP as the rate of organic matter production in photosynthesis (½ mark)
  • NPP is available to heterotrophs (½ mark)
  • Part of GPP is used in plant respiration (½ mark)

Revise the chapter

Practise this chapterBoard-style questions from Ecosystem, one at a time, marked against the answer key and marking points.Back to the full paper2025 board paper, set 57/1/1: every question, by section.

The question is transcribed from the official paper; figures are described in words. The solution, hints and chapter tag are ours. Spotted an error? Write tosupport@questionbuddy.in.