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(i) Why is there a… (Class 12 Biology SQP 2024-25, Q33A)

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BiologyCBSE Class 12 · Sample paper, session 2024-25 · 5 marks · Long answer

CBSE Class 12 Biology sample paper 2024-25: question 33(A)

From the official CBSE sample question paper for 2024-25, section E, question 33(A), for 5 marks. Try it first; the hints and our step-by-step solution are below.

Q33(A) · 5 marks · Long answerBiodiversity and Conservation

(i) Why is there a need to conserve biodiversity? (Any two reasons)
(ii) Name and explain any two causes that are responsible for the loss of biodiversity.

Source: official sample paper from cbseacademic.nic.in (PDF). See it in the full Sample paper 2024-25.

Hints

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

Hint 1

The reasons fall into three groups: utilitarian in a narrow sense, utilitarian in a broad sense, and ethical.

Hint 2

For the causes, recall the 'Evil Quartet'.

Hint 3

Habitat loss, over-exploitation, alien species and co-extinction: give one example for each cause you choose (e.g. Nile perch, 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. (i) Reason 1: Narrowly utilitarian. Humans get direct economic benefits from biodiversity. These include food, firewood, fibre, construction material, industrial products (resins, gums, dyes, tannins) and medicinally important products.

    1 mark

  2. (i) Reason 2: Broadly utilitarian. Biodiversity sustains many ecosystem services. For example, the Amazon forest is estimated to produce about 20% of the earth's atmospheric oxygen, and pollinators such as bees, birds and bats help plants form fruits and seeds. Biodiversity also gives aesthetic pleasures such as bird watching.

    (Alternatively, ethical reason: every species has intrinsic value even without economic value, so it is our moral duty to protect all living creatures for future generations.)

    1 mark

  3. (ii) Cause 1: Habitat loss and fragmentation. This is the primary cause of extinction. Examples include clearing of tropical rainforests. When large habitats are broken up by human settlements, roads and canals, populations of animals needing large territories, and of migratory animals, decline.

    1½ marks

  4. (ii) Cause 2: Over-exploitation. When humans over-harvest natural resources, species are degraded and driven to extinction. Examples: Steller's sea cow, the passenger pigeon and many marine fishes.

    (Other accepted causes: alien species invasion, e.g. Nile perch introduced into Lake Victoria wiped out the native cichlid fishes; co-extinction, e.g. parasites that depend only on a host fish die out when the host becomes extinct.)

    1½ marks

Answer: (i) Narrowly utilitarian (direct products such as food, fibre and medicines) and broadly utilitarian (ecosystem services such as oxygen and pollination); the ethical reason is also accepted. (ii) Habitat loss and fragmentation, and over-exploitation (alien species invasion and co-extinction are also accepted).

Where the marks are

  • First reason for conservation explained with examples (1 mark)
  • Second reason for conservation explained with examples (1 mark)
  • First cause of biodiversity loss named and explained with an example (1.5 marks)
  • Second cause of biodiversity loss named and explained with an example (1.5 marks)

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 paperSample paper 2024-25: 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.