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Answer the following. (Class 10 Science 2025, Q35A)

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ScienceCBSE Class 10 · Board exam 2025, set 31/5/1 · 5 marks · Long answer

CBSE Class 10 Science 2025: question 35(A)

Set in the CBSE Class 10 board exam of 2025, paper 31/5/1, section D, question 35(A), for 5 marks. Try it first; the hints and our step-by-step solution are below.

Q35(A) · 5 marks · Long answerCompetency-basedControl and Coordination

Answer the following.

  1. (a)

    Analyse the given situations and interpret the possible reason for each: (i) Iodine deficiency in diet increases the possibility of a disease of swollen neck in a person. (ii) Some people in population may have very short heights (dwarfs). (iii) Thick facial hairs develop in boys at the age of 10-12 years.

    0 marks
  2. (b)

    Explain two reasons which necessitate the need of chemical communication in multicellular organisms.

    0 marks

Source: official question paper from cbse.gov.in (PDF). See it in the full 2025 board paper, set 31/5/1.

Hints

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

Hint 1

Link each situation to a gland: thyroid, pituitary, testes.

Hint 2

Compare nerve impulses with hormones: which can reach every cell and keep acting for a long time?

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. (a)(i) Iodine is needed by the thyroid gland to make the hormone thyroxin. When iodine is deficient, thyroxin is not made properly and the thyroid swells, causing goitre (swollen neck).

    1 mark

  2. (a)(ii) Growth hormone from the pituitary gland controls growth. Its deficiency in childhood leads to dwarfism.

    1 mark

  3. (a)(iii) At puberty the testes secrete the hormone testosterone, which causes changes such as growth of facial hair in boys.

    1 mark

  4. (b) Reason 1: Electrical impulses reach only the cells connected to nerve tissue. Hormones released into the blood can reach all cells of the body.

    1 mark

  5. (b) Reason 2: Hormones act steadily and persistently, which is needed to coordinate long-term processes like growth, development and responses to the environment. Nerve cells cannot generate impulses continuously.

    1 mark

Answer: (a)(i) Low iodine → less thyroxin → goitre; (ii) growth hormone deficiency → dwarfism; (iii) testosterone at puberty; (b) hormones reach all cells and act steadily, coordinating growth and development.

Where the marks are

  • Iodine needed for thyroxin; deficiency causes goitre (1 mark)
  • Growth hormone deficiency causes dwarfism (1 mark)
  • Testosterone secretion at puberty (1 mark)
  • Hormones can reach all cells of the body (1 mark)
  • Hormones act steadily/persistently to coordinate growth and development (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 paper2025 board paper, set 31/5/1: 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.