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Explain how some harmful… (Class 10 Science 2023, Q33)

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ScienceCBSE Class 10 · Board exam 2023, set 31/2/1 · 3 marks · Short answer

CBSE Class 10 Science 2023: question 33

Set in the CBSE Class 10 board exam of 2023, paper 31/2/1, 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

Explain how some harmful chemicals enter our bodies through the food chain. Why is the concentration of these harmful chemicals found to be maximum in human beings ?

Source: official question paper from cbse.gov.in (PDF). See it in the full 2023 board paper, set 31/2/1.

Hints

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

Hint 1

Start with the chemicals farmers spray on crops. Where do they go when it rains?

Hint 2

These chemicals cannot be broken down. What happens to them as they move from plants to animals to us?

Hint 3

Where do humans sit in a food chain?

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. Farmers use chemicals such as pesticides and fertilisers to protect and grow crops. Rain washes these chemicals into the soil and water bodies. Plants absorb them along with water and minerals, and aquatic animals take them in from the water.

    1 mark

  2. These chemicals are non-biodegradable, so they are not broken down in organisms. When animals eat these plants, and we eat the plants or animals (for example grains, vegetables, fish or milk), the chemicals pass from one trophic level to the next. In this way they enter our bodies.

    1 mark

  3. Human beings occupy the topmost trophic level in most food chains. The chemicals keep accumulating at each successive level (biological magnification). Hence their concentration is maximum in human beings.

    1 mark

Answer: Pesticides reach soil and water, are absorbed by plants and animals, and pass up the food chain into humans; humans are at the top level, so biomagnification makes the concentration maximum in them.

Where the marks are

  • Explains how pesticides enter soil and water and are absorbed by plants and animals, then reach us through food (2 marks)
  • Humans occupy the top trophic level, so the chemicals accumulate most in them (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 31/2/1: 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.