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In the following food chain… (Class 10 Science 2023, Q26)

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ScienceCBSE Class 10 · Board exam 2023, set 31/5/1 · 2 marks · Very short answer

CBSE Class 10 Science 2023: question 26

Set in the CBSE Class 10 board exam of 2023, paper 31/5/1, section B, question 26, for 2 marks. Try it first; the hints and our step-by-step solution are below.

Q26 · 2 marks · Very short answerCompetency-basedOur Environment

In the following food chain, if 50 J of energy was available to the hawk, how much energy would have been present at the first and third tropic levels ? Justify your answer.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2023 board paper, set 31/5/1.

Hints

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

Hint 1

Number the trophic levels starting with grass as the first.

Hint 2

What fraction of energy is passed from one level to the next?

Hint 3

Go backwards from the hawk, multiplying by the same factor at each step.

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. Trophic levels: Grass (1st) → Grasshopper (2nd) → Frog (3rd) → Snake (4th) → Hawk (5th). Working back from the hawk, each lower level has 10 times the energy: Hawk 50 J → Snake 500 J → Frog 5000 J → Grasshopper 50,000 J → Grass 5,00,000 J.

  2. Energy at the first trophic level (grass) = 5,00,000 J

    ½ mark

  3. Energy at the third trophic level (frog) = 5000 J

    ½ mark

  4. Justification (10% law): only about 10% of the energy at one trophic level is passed on to the next level. The rest is used for life processes or lost as heat.

    1 mark

Answer: First trophic level: 5,00,000 J; third trophic level: 5000 J (10% law)

Where the marks are

  • First trophic level energy = 5,00,000 J (½ mark)
  • Third trophic level energy = 5000 J (½ mark)
  • Justifies using the 10% law of energy transfer (1 mark)

Revise the chapter

  • Chapter: Our Environment (notes, formulas, where marks are lost and every past question)
Practise this chapterBoard-style questions from Our Environment, one at a time, marked against the answer key and marking points.Back to the full paper2023 board paper, set 31/5/1: 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.