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Ecological pyramids are… (Class 12 Biology 2026, Q21b)

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BiologyCBSE Class 12 · Board exam 2026, set 57/5/1 · 2 marks · Very short answer

CBSE Class 12 Biology 2026: question 21(b)

Set in the CBSE Class 12 board exam of 2026, paper 57/5/1, section B, question 21(b), for 2 marks. Try it first; the hints and our step-by-step solution are below.

Q21(b) · 2 marks · Very short answerEcosystem

Ecological pyramids are widely accepted but they still have some limitations. Write any two limitations.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2026 board paper, set 57/5/1.

Hints

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

Hint 1

Think of an animal like a sparrow that eats both seeds and insects. Where would it be placed in a pyramid?

Hint 2

Which important group of organisms that break down dead matter is missing from pyramids?

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. Ecological pyramids do not take into account that the same species may belong to two or more trophic levels.

    1 mark

  2. They assume a simple food chain, which almost never exists in nature, and so do not accommodate a food web. Also, saprophytes/decomposers are given no place in the pyramids even though they play a vital role in the ecosystem.

    1 mark

Answer: Same species at more than one trophic level is ignored; they assume simple food chains (no food webs) and leave out saprophytes.

Where the marks are

  • One valid limitation, e.g. a species occupying more than one trophic level is ignored (1 mark)
  • A second valid limitation, e.g. assumes a simple food chain and not a food web, or saprophytes are not included (1 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 paper2026 board paper, set 57/5/1: 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.