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Select the option that gives… (Class 12 Biology 2023, Q7)

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BiologyCBSE Class 12 · Board exam 2023, set 57/1/1 · 1 mark · MCQ

CBSE Class 12 Biology 2023: question 7

Set in the CBSE Class 12 board exam of 2023, paper 57/1/1, section A, question 7, for 1 mark. Try it first; the hints and our step-by-step solution are below.

Q7 · 1 mark · MCQCompetency-basedEvolution

Select the option that gives the correct description of the process of Natural Selection with respect to the length of the neck of giraffe.

  1. (A)Stabilising selection as giraffes with longer neck lengths are selected further.
  2. (B)Disruptive selection as giraffes with smaller and longer neck lengths are selected.
  3. (C)Directional selection as giraffes with longer neck lengths are selected.
  4. (D)Stabilising selection as giraffes with medium neck lengths are selected.

Figure in the paper: Bell-shaped curve; y-axis: number of giraffes, x-axis: neck length in giraffe, with the peak at the middle (medium neck length). See it in the official paper.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2023 board paper, set 57/1/1.

Hints

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

Hint 1

Where is the peak of the curve?

Hint 2

Which type of selection favours the mean value?

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. The curve peaks at medium neck length, which means the average phenotype is favoured. That is stabilising selection with medium-necked giraffes selected, so option (D) is correct for the graph shown.

    1 mark

  2. The scheme also accepts (C), directional selection, on the basis of the classic account of giraffe evolution.

Answer: Option (D): stabilising selection (scheme also accepts C)

Where the marks are

  • Recognises stabilising selection from a curve that peaks at the middle (1 mark)

Revise the chapter

Practise this chapterBoard-style questions from Evolution, one at a time, marked against the answer key and marking points.Back to the full paper2023 board paper, set 57/1/1: 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.