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A tropical rainforest… (Class 12 Biology SQP 2025-26, Q21B)

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BiologyCBSE Class 12 · Sample paper, session 2025-26 · 2 marks · Very short answer

CBSE Class 12 Biology sample paper 2025-26: question 21(B)

From the official CBSE sample question paper for 2025-26, section B, question 21(B), for 2 marks. Try it first; the hints and our step-by-step solution are below.

Q21(B) · 2 marks · Very short answerCompetency-basedBiodiversity and Conservation

A tropical rainforest in South America is home to more than 40,000 species of plants, 3,000 of fishes, 1,300 of birds, 427 of mammals, 427 of amphibians, 378 of reptiles and 1,25,000 insects, snails and worms.
From the given data, calculate the total number of known vertebrate species in the rainforest.
(i) Give a reason to justify the huge difference in the number of plant and animal species.

Source: official sample paper from cbseacademic.nic.in (PDF). See it in the full Sample paper 2025-26.

Hints

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

Hint 1

Leave out plants and invertebrates (insects, snails, worms) from the sum.

Hint 2

Compare how plants and animals cope with environmental change.

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. Vertebrates are fishes, birds, mammals, amphibians and reptiles:
    vertebrate species.

    1 mark

  2. (i) Reason: Animals are mobile and have complex nervous systems and receptors. They can migrate away from harsh conditions and respond adaptively, so fewer separate species are needed. Plants are fixed and must adapt locally to water, minerals and sunlight in every microhabitat. Also, energy available falls at higher trophic levels (10% law), so producers can support only a limited number of vertebrate species.

    1 mark

Answer: (i) 5532 vertebrate species; difference due to mobility/adaptive responses of animals vs fixed plants (and reduced energy at higher trophic levels).

Where the marks are

  • Adds fishes, birds, mammals, amphibians, reptiles = 5532 (1 mark)
  • Any one valid reason, e.g. mobility and adaptive responses of animals vs sessile plants (1 mark)

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 2025-26: 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.