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Answer the following. (Class 10 Science 2025, Q26)

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ScienceCBSE Class 10 · Board exam 2025, set 31/5/1 · 2 marks · Very short answer

CBSE Class 10 Science 2025: question 26

Set in the CBSE Class 10 board exam of 2025, 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 answerOur Environment

Answer the following.

  1. (a)

    Why are the organisms of first trophic level important in any food chain?

    1 mark
  2. (b)

    Justify the following statement: 'The flow of energy in an ecosystem is unidirectional.'

    1 mark

Source: official question paper from cbse.gov.in (PDF). See it in the full 2025 board paper, set 31/5/1.

Hints

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

Hint 1

Where does the energy of every food chain originally come from, and who captures it?

Hint 2

Can energy taken in by a herbivore ever go back to the grass or to the sun?

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) First-trophic-level organisms are the producers (green plants). They trap solar energy and convert it into chemical energy in food. This makes energy available to all the consumers (heterotrophs), so no food chain can exist without them.

    1 mark

  2. (b) Energy trapped by autotrophs never goes back to the sun, and energy passed to herbivores never returns to the producers. Energy moves only forward from one trophic level to the next and is no longer available to the previous level. Hence the flow of energy is unidirectional.

    1 mark

Answer: (a) Producers fix solar energy and make it available to consumers; (b) energy passes forward only and never returns to the sun or to earlier trophic levels.

Where the marks are

  • States that producers fix solar energy and make it available to consumers (1 mark)
  • Justifies that energy does not revert to the sun or to previous trophic levels (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 paper2025 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.