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Tropical regions harbour… (Class 12 Biology 2024, Q23a)

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

CBSE Class 12 Biology 2024: question 23(a)

Set in the CBSE Class 12 board exam of 2024, paper 57/5/1, section C, question 23(a), for 3 marks. Try it first; the hints and our step-by-step solution are below.

Q23(a) · 3 marks · Short answerBiodiversity and Conservation

Tropical regions harbour more species than the temperate regions. How have biologists tried to explain this in their own ways ? Explain.

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

Think about the history of ice ages in temperate versus tropical regions.

Hint 2

How does a stable, predictable climate affect specialisation of organisms?

Hint 3

Which region receives more sunlight, and what does that mean for productivity?

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. Hypothesis 1 – Long evolutionary time: Temperate regions went through frequent glaciations in the past. Tropical regions have stayed relatively undisturbed for millions of years, so they have had a long evolutionary time for species diversification.

    1 mark

  2. Hypothesis 2 – Stable environment: Tropical environments are less seasonal, relatively constant and predictable. Such constant conditions promote niche specialisation, which leads to greater species diversity.

    1 mark

  3. Hypothesis 3 – More solar energy: Tropical regions receive more solar energy. This contributes to higher productivity, which can support more species.

    1 mark

Answer: Three explanations: (1) no past glaciations, giving a long evolutionary time; (2) a less seasonal, stable environment promoting niche specialisation; (3) more solar energy, giving higher productivity.

Where the marks are

  • Absence of frequent glaciation, giving long evolutionary time for diversification (1 mark)
  • Less seasonal, constant and predictable environment promoting niche specialisation (1 mark)
  • More solar energy leading to higher productivity (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 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.