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Explain Gause's 'Competitive… (Class 12 Biology 2026, Q27)

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BiologyCBSE Class 12 · Board exam 2026, set 57/5/1 · 3 marks · Short answer

CBSE Class 12 Biology 2026: question 27

Set in the CBSE Class 12 board exam of 2026, paper 57/5/1, section C, question 27, for 3 marks. Try it first; the hints and our step-by-step solution are below.

Q27 · 3 marks · Short answerOrganisms and Populations

Explain Gause's 'Competitive Exclusion Principle' with the help of a suitable example.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2026 board paper, set 57/5/1.

Hints

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

Hint 1

The principle concerns competition when a resource is limited.

Hint 2

Recall the Galapagos example where an introduced browsing animal drove a native reptile to extinction.

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. Statement: Gause's competitive exclusion principle states that two closely related species competing for the same limited resources cannot co-exist indefinitely.

    1 mark

  2. The competitively inferior species is eventually eliminated, because the superior competitor uses the limited resource more efficiently and dominates.

    1 mark

  3. Example: The Abingdon tortoise of the Galapagos Islands became extinct within about a decade after goats were introduced on the island. This was probably because the goats browsed more efficiently. (Another example: in some shallow South American lakes, visiting flamingoes and resident fishes compete for the same food, zooplankton.)

    1 mark

Answer: Closely related species competing for the same limited resource cannot co-exist indefinitely; the inferior one is eliminated. Example: Abingdon tortoise eliminated by introduced goats.

Where the marks are

  • States that closely related species competing for the same limited resource cannot co-exist indefinitely (1 mark)
  • States that the inferior competitor is eliminated (1 mark)
  • Gives a suitable example, e.g. goats and Abingdon tortoise, or flamingoes and fishes (1 mark)

Revise the chapter

Practise this chapterBoard-style questions from Organisms and Populations, one at a time, marked against the answer key and marking points.Back to the full paper2026 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.