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Answer the following. (Science 2024 31/2/1 Q35b)

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ScienceCBSE Class 10 · Board exam 2024, set 31/2/1 · 5 marks · Long answer

CBSE Class 10 Science 2024: question 35(b)

Set in the CBSE Class 10 board exam of 2024, paper 31/2/1, section D, question 35(b), for 5 marks. Try it first; the hints and our step-by-step solution are below.

Q35(b) · 5 marks · Long answerControl and Coordination

Answer the following.

  1. (i)

    What are tropic movements ? Give an example of a plant hormone which (1) inhibits growth and (2) promotes cell division.

    0 marks
  2. (ii)

    Explain directional movement of a tendril in pea plant in response to touch. Name the hormone responsible for this movement.

    0 marks

Source: official question paper from cbse.gov.in (PDF). See it in the full 2024 board paper, set 31/2/1.

Hints

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

Hint 1

'Tropic' movements depend on the direction of the stimulus.

Hint 2

Think which hormone causes wilting and which one is rich in fruits and seeds.

Hint 3

Coiling happens when one side of the tendril grows faster than the other. Which hormone controls such growth?

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) Tropic movements are directional growth movements of a plant part in response to an external stimulus such as light, gravity, water, chemicals or touch. The growth is towards the stimulus (positive) or away from it (negative). Example: a shoot bends towards light (phototropism).

    1 mark

  2. (i)(1) A plant hormone that inhibits growth: abscisic acid (ABA). It also causes wilting of leaves.

    ½ mark

  3. (i)(2) A plant hormone that promotes cell division: cytokinin.

    ½ mark

  4. (ii) The tendril of a pea plant is sensitive to touch (thigmotropism). When it touches a support, auxin moves away from the point of contact towards the opposite side.

    1 mark

  5. (ii) The side of the tendril away from the support therefore grows faster than the side in contact with it. This unequal growth on the two sides makes the tendril bend and coil around the support.

    1 mark

  6. (ii) Hormone responsible: auxin.

    1 mark

Answer: (i) Directional growth movements in response to a stimulus; (1) abscisic acid, (2) cytokinin. (ii) Unequal growth on the two sides makes the tendril coil around the support; hormone: auxin

Where the marks are

  • Defines tropic movement as directional growth movement in response to a stimulus (1 mark)
  • Abscisic acid as the growth inhibitor (½ mark)
  • Cytokinin as the promoter of cell division (½ mark)
  • Explains auxin moving away from the contact point, faster growth on the far side and coiling (2 marks)
  • Names auxin (1 mark)

Revise the chapter

Practise this chapterBoard-style questions from Control and Coordination, one at a time, marked against the answer key and marking points.Back to the full paper2024 board paper, set 31/2/1: 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.