NCERT Class VIII Science Solutions: Chapter 10-Reaching the age of Adolescence Part 2

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Question 5:

Prepare a Table having two columns depicting names of endocrine glands and hormones secreted by them.

Answer:

Endocrine glands and hormones secreted

S. No.

Endocrine Gland

Hormone Secreted

1.

Pituitary

Growth Hormones

2.

Thyroid

Thyroxin

3.

Adrenal

Adrenalin

4.

Pancreas

Insulin

5.

Testes

Testosterone

6.

Ovaries

Estrogen & Progesterone

Question 6:

What are sex hormones? Why are they named so? State their function.

Answer:

Hormones which constitute the secondary sexual characters are called sex hormones. In general, hormones work instantly when they released in blood stream. Sex hormones are different because they start to work later on. They gradually prepare in the body for reproduction.

The sex hormones are responsible for the fundamental change in growth & development and stimulate the developments of secondary sexual characters. The testes and the ovaries are the reproductive Organs and both are stimulated by the pituitary hormone during Puberty. That's the reason these are called sex hormones.

Functions of Sex Hormones:

  • In male, the testes produces the male sex hormone testosterone. This hormone helps in the development and maintenance of the primary and secondary sexual characters and production of sperms.

  • In female, the ovaries secrete estrogen and progesterone responsible for the primary and secondary sexual characters.

Question 7:

Choose the correct option.

  1. Adolescents should be careful about what they eat, because.

  2. Proper diet develops their brains.

  3. Proper diet is needed for the rapid growth taking place in their body.

  4. Adolescents feel hungry all the time.

  5. Taste buds are well developed in teenagers.

  6. Reproductive age in women starts when there.

  7. Menstruation starts.

  8. Breasts start developing.

  9. Body weight increases.

  10. Height increases.

  11. The right meal for adolescents consists of

  12. Chips, noodles, coke.

  13. Chapatti, dal, vegetables.

  14. Rice, noodles and burger.

  15. Vegetable cutlets, chips and lemon drink.

Answer:

  1. Adolescents should be careful about what they eat, because proper diet is needed for the rapid growth taking place in their body.

  2. Reproductive age in women starts when their menstruation starts.

  3. The right meal for adolescents consists of chapatti, dal, and vegetables.

Question 8:

Write notes on

  1. Adam’s apple.

  2. Secondary sexual characters.

  3. Sex determination in the unborn baby.

Answer:

  1. Adam’s apple: The protruding part of the throat is called Adam’s apple. It is the enlarged voice box or larynx which gets enlarged and visible from outside in boys at the onset of puberty. This makes the voice of boys hoarse.

  2. Secondary sexual characters: Secondary Sexual Characters are those characters which distinguish a male from female. Some of the characters are as follows:

Boys:

  • 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.

Girls:

  • 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.

  1. Sex determination in the unborn baby: All human beings have 23 pairs of chromosomes in the nuclei of their cells. Out of these two chromosomes are the sex chromosomes, named X and Y. A female has two X chromosomes, while a male has one X and one Y chromosome. The gametes (egg and sperm) have only one set of chromosomes. The unfertilized egg always has one X chromosome but sperms may have X or Y. When a sperm containing X chromosome fertilizes the egg, the zygote would have two X chromosomes and develop into a female child. If the sperm contributes a Y chromosome to the egg (ovum) at fertilization, the zygote would develop into a male child. This concludes that the sex chromosomes of the father determine the sex of an unborn baby.

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Sex Determination in the Unborn Baby

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