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We do not clean natural ponds… (Class 10 Science 2025, Q26)

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ScienceCBSE Class 10 · Board exam 2025, set 31/6/1 · 2 marks · Very short answer

CBSE Class 10 Science 2025: question 26

Set in the CBSE Class 10 board exam of 2025, paper 31/6/1, 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

We do not clean natural ponds or lakes whereas an aquarium or a swimming pool needs to be cleaned regularly. Why ?

Source: official question paper from cbse.gov.in (PDF). See it in the full 2025 board paper, set 31/6/1.

Hints

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

Hint 1

Which group of organisms breaks down dead matter and wastes in nature?

Hint 2

Compare a natural ecosystem with a man-made one: which one has a complete set of organisms?

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. Ponds and lakes are natural, self-sustaining ecosystems. Decomposers such as bacteria and fungi break down dead matter and wastes there, and nutrients are recycled, so they clean themselves naturally.

    1 mark

  2. An aquarium or a swimming pool is an artificial (man-made) ecosystem with few or no decomposers. Wastes keep building up and become harmful to fish, plants or swimmers, so these must be cleaned regularly.

    1 mark

Answer: Natural ponds have decomposers that break down wastes; aquaria and pools are artificial ecosystems lacking decomposers, so wastes accumulate.

Where the marks are

  • Ponds/lakes are natural ecosystems where decomposers break down wastes (1 mark)
  • Aquarium/pool is an artificial ecosystem without decomposers, so wastes build up and must be cleaned (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 31/6/1: 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.