Skip to content

Explain why food chains… (Class 10 Science 2026, Q11)

questionbuddy.in/q/cbse-10-science-2026-31-4-1-q11-food-chains-generally-consist-steps

ScienceCBSE Class 10 · Board exam 2026, set 31/4/1 · 2 marks · Very short answer

CBSE Class 10 Science 2026: question 11

Set in the CBSE Class 10 board exam of 2026, paper 31/4/1, section A, question 11, for 2 marks. Try it first; the hints and our step-by-step solution are below.

Q11 · 2 marks · Very short answerOur Environment

Explain why food chains generally consist of three or four steps.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2026 board paper, set 31/4/1.

Hints

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

Hint 1

Recall what fraction of energy passes from one trophic level to the next.

Hint 2

Start with 1000 units of energy at the producer and find how much is left at the fourth level.

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. By the 10% law, only about 10% of the energy at one trophic level is passed on to the next level. The remaining energy is used for life processes or lost as heat.

    1 mark

  2. So the usable energy falls sharply at each step. For example: Grass (1000 kJ) → Grasshopper (100 kJ) → Frog (10 kJ) → Snake (1 kJ). After three or four steps too little energy is left to support another level, so food chains usually have only 3–4 steps.

    1 mark

Answer: Only about 10% of energy passes to the next trophic level, so after 3–4 levels too little energy remains to support further organisms.

Where the marks are

  • States the 10% law, with most energy lost as heat (1 mark)
  • Concludes that very little energy remains after 3–4 levels, or shows this with an energy-flow example (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 paper2026 board paper, set 31/4/1: 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.