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How do harmful chemicals get… (Class 10 Science 2023, Q26)

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

CBSE Class 10 Science 2023: question 26

Set in the CBSE Class 10 board exam of 2023, paper 31/1/1, 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

How do harmful chemicals get accumulated progressively at each trophic level in a food chain ?

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

Hints

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

Hint 1

Start from pesticides sprayed on a field. How do they reach plants?

Hint 2

Why are these chemicals not removed from the body, and what happens when a predator eats many contaminated prey?

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. Entry into the food chain: Pesticides and other chemicals sprayed on crops are washed into the soil and water bodies. Plants absorb them from the soil along with water and minerals. Animals then eat these plants, so the chemicals enter the food chain.

    1 mark

  2. Progressive accumulation: These chemicals are non-biodegradable, so they are neither broken down nor excreted. At every step, each organism eats many organisms of the lower trophic level. The chemical therefore keeps building up, and its concentration increases at each successive trophic level. It is highest in the top consumers, such as humans. This is called biological magnification.

    1 mark

Answer: Non-biodegradable chemicals from crops pass from the soil to plants and then to animals. Because they cannot be broken down, their concentration builds up at each trophic level. This is biological magnification.

Where the marks are

  • Explains how chemicals enter the food chain via soil, water and plants (1 mark)
  • Non-biodegradable chemicals accumulate at each successive trophic level, called biomagnification (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 31/1/1: 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.