NCERT Class VIII Science Solutions: Chapter 10-Reaching the age of Adolescence Part 1

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Question 1:

What is the term used for secretions of endocrine glands responsible for changes taking place in the body?

Answer:

Hormones are chemical messengers that transport signal from one cell (or gland) to another cell (or gland).

Question 2:

Define adolescence.

Answer:

The period of life, when the body undergoes changes, leading to reproductive maturity, is called adolescence. Adolescence begins around the age of 11 and lasts up to 18 or 19 years of age.

This diagram shows cycle of adolescence

Cycle of Adolescence

This diagram shows cycle of adolescence

Question 3:

What is menstruation? Explain.

Answer:

In a female reproductive ovaries, the ova begin to mature with the onset of puberty. One ovum matures and released by one of the ovaries once in about 28 to 30 days. During this period, the wall of the uterus becomes thick so as to receive the egg, in case it is fertilized and begins to develop. If fertilization does not occur, the released egg and the thickened lining of the uterus along with its blood vessels are shed off. This causes bleeding in female which is called menstruation. Menstruation occurs once in about 28 to 30 days.

Question 4:

List changes in the body that take place at puberty.

Answer:

  • Common changes occur among boys and girls during puberty:

  • Sudden increase in height.

  • Change in body shape.

  • Change in voice. In boys voice becomes deep and harsh, in girls it is high pitched voice.

  • Increased activity of sweat and sebaceous glands.

  • Reproductive organs begin to mature.

  • Appearance of secondary sexual characteristics.

Changes in Boys during puberty:

  • Facial hairs such as beard and moustaches develop.

  • Hair develops under the armpit, under chest and in the pubic regions.

  • Voice becomes deeper.

  • Muscles develop, and shoulder becomes broad.

  • Increase in weight.

Changes in Girls during puberty:

  • Development and enlargement of breasts.

  • Hair develops under the armpit and in the pubic regions.

  • Hips broaden and pelvic region widens.

  • Initiation of menstrual cycle.

  • Deposition of fat around hips.