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Ecological pyramids give… (Class 12 Biology 2023, Q20)

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BiologyCBSE Class 12 · Board exam 2023, set 57/1/1 · 2 marks · Very short answer

CBSE Class 12 Biology 2023: question 20

Set in the CBSE Class 12 board exam of 2023, paper 57/1/1, section B, question 20, for 2 marks. Try it first; the hints and our step-by-step solution are below.

Q20 · 2 marks · Very short answerEcosystem

Ecological pyramids give important information about the ecological system, but do have some limitations. List any two limitations of ecological pyramids.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2023 board paper, set 57/1/1.

Hints

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

Hint 1

Can one organism, such as a sparrow, feed at more than one level?

Hint 2

Does nature have simple chains or interconnected webs? Where are decomposers in a pyramid?

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. 1. Ecological pyramids do not take into account the same species belonging to two or more trophic levels.

    1 mark

  2. 2. They assume a simple food chain, which almost never exists in nature, and so cannot accommodate a food web.

    (Also acceptable: saprophytes/decomposers are given no place in the pyramid, although they play a vital ecological role.)

    1 mark

Answer: No account of a species occupying more than one trophic level; assumes a simple food chain (ignores food webs); saprophytes not included – any two

Where the marks are

  • Same species at two or more trophic levels not considered (1 mark)
  • Assumes a simple food chain and ignores food webs, or saprophytes not given a place (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 paper2023 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.