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Answer the following. (Class 10 Science 2023, Q33)

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ScienceCBSE Class 10 · Board exam 2023, set 31/6/1 · 3 marks · Short answer

CBSE Class 10 Science 2023: question 33

Set in the CBSE Class 10 board exam of 2023, paper 31/6/1, section C, question 33, for 3 marks. Try it first; the hints and our step-by-step solution are below.

Q33 · 3 marks · Short answerOur Environment

Answer the following.

  1. (a)

    Write the percentage of (i) solar energy captured by the autotrophs and (ii) energy transferred from autotrophs to the next level in a food chain.

    0 marks
  2. (b)

    What are trophic levels? Why do different food chains in an ecosystem not have more than four to five trophic levels? Give reason.

    0 marks

Source: official question paper from cbse.gov.in (PDF). See it in the full 2023 board paper, set 31/6/1.

Hints

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

Hint 1

Recall the 10% law of energy flow.

Hint 2

Work out what fraction of the original energy is left after four transfers of 10% each.

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. (a)(i) Autotrophs capture about 1% of the solar energy falling on their leaves.

    ½ mark

  2. (a)(ii) About 10% of the energy is transferred from the autotrophs to the next trophic level.

    ½ mark

  3. (b) Trophic levels are the various steps in a food chain at which energy is transferred, e.g. producers, herbivores, carnivores.

    1 mark

  4. Only about 10% of the energy passes on at each level, so the usable energy keeps decreasing. After four or five trophic levels, too little energy is left to support another level.

    1 mark

Answer: (a) (i) 1%; (ii) 10%; (b) trophic levels are steps of energy transfer in a food chain; energy decreases at each level, so too little remains beyond 4–5 levels.

Where the marks are

  • 1% (½ mark)
  • 10% (½ mark)
  • Definition of trophic level (1 mark)
  • Reason based on energy loss at each level (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 31/6/1: 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.