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The world is facing… (Class 12 Biology 2024, Q28)

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BiologyCBSE Class 12 · Board exam 2024, set 57/5/1 · 3 marks · Short answer

CBSE Class 12 Biology 2024: question 28

Set in the CBSE Class 12 board exam of 2024, paper 57/5/1, section C, question 28, for 3 marks. Try it first; the hints and our step-by-step solution are below.

Q28 · 3 marks · Short answerBiodiversity and Conservation

The world is facing accelerated rates of species extinction largely due to human activities. Explain any three human activities responsible for accelerated rates of species extinction.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2024 board paper, set 57/5/1.

Hints

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

Hint 1

Recall the 'Evil Quartet' from the chapter on Biodiversity.

Hint 2

Think of forests being cleared, species being hunted, and species being introduced into new places.

Hint 3

Back up each cause with a named example such as Lake Victoria or Steller's sea cow.

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. 1. Habitat loss and fragmentation – this is the most important cause of extinction.

    ½ mark

  2. For example, tropical rain forests such as the Amazon are cleared for soybean cultivation and cattle pastures. Large habitats get broken into fragments, so animals needing large territories and migratory animals decline.

    ½ mark

  3. 2. Over-exploitation – humans take natural resources at a rate faster than they can be replenished.

    ½ mark

  4. For example, Steller's sea cow and the passenger pigeon became extinct due to over-hunting, and many marine fish populations are over-harvested.

    ½ mark

  5. 3. Alien species invasion – introduced species can drive indigenous species towards extinction.

    ½ mark

  6. For example, the Nile perch introduced into Lake Victoria caused the extinction of more than 200 species of cichlid fish. Similarly, the illegally introduced African catfish Clarias gariepinus threatens native catfishes. (Co-extinction or pollution, with an example, are also acceptable.)

    ½ mark

Answer: Any three: habitat loss and fragmentation (Amazon forest clearing), over-exploitation (Steller's sea cow, passenger pigeon), alien species invasion (Nile perch in Lake Victoria); also co-extinction or pollution.

Where the marks are

  • Each of three human activities named (½ mark each)
  • A correct explanation or example for each activity (½ mark each)

Revise the chapter

Practise this chapterBoard-style questions from Biodiversity and Conservation, one at a time, marked against the answer key and marking points.Back to the full paper2024 board paper, set 57/5/1: 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.