NCERT Solutions class 8 Science 10. Reaching the age of adolescence Text Book Exercise

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Exercise

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

Answer : The term used for secretions of endocrine glands is hormoane which is responsible for various changes taking place in the body.

2. Define adolescence.

Answer : The period of life when the body undergors changes, leading to reproductive maturity, is called adolescence.

3. What is menstruation? Explain.

Answer : When the uterus receives the egg and it is fertilized, pregnacy occurs. If fertilization does not occur, the released egg and the thickened lining of the uterus along with its blood vesssels are shed off. This causes bleeding in women which is called menstruation. 

4. List changes in the body that take place at puberty.

Answer : The onset of puberty brings about :

(i) Growth of the reproductive organs which begin to function. (ii) Hair grows at various places of the body. Breasts develop in girl and facial hair (moustache and beard)  apper in boys. 

(iii) Voice of the boys becomes hoarse as voice box enlarges during adolescence. 

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

Answer: 

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

Answer:

Hormones secreted by testes and ovaries are termed as sex-hormones.

  They are named so because they are secreted by the reproductive organs.

Function of sex-hormones:

  They hormones are responsible for the secondary sexual charaters of male and female.

7. Choose the correct option.

(a) Adolescents should be careful about what they eat, because

(i) proper diet develops their brains.

(ii) proper diet is needed for the rapid growth taking place in their body.

(iii) adolescents feel hungry all the time.

(iv) taste buds are well developed in teenagers.

(b) Reproductive age in women starts when their

(i) menstruation starts.

(ii) breasts start developing.

(iii) body weight increases.

(iv) height increases.

(c) The right meal for adolescents consists of

(i) chips, noodles, coke.

(ii) chapati, dal, vegetables.

(iii) rice, noodles and burger.

(iv) vegetable cutlets, chips and lemon drink.

Answer:

(a) (ii), (b) (i), (c) (ii).

8. Write notes on—

(a) Adam’s apple.

(b) Secondary sexual characters.

(c) Sex determination in the unborn baby.

Answer:

(a) Adam's apple: In human males, the larynx grows larger during puberty and can be seen as a protruding part of the throat. This protrusion is known as the Adam's apple. In boys, under the influence of sex hormones, the larynx becomes prominent, As a result, the vocal cords become longer and thicker, causing the voice to become hoarse.

Concept insight: At puberty, boys develop a larger voice box called Adam's apple.

(b) Secondary sexual characters are those features that help in distinguishing the male and the female body from each other. They are physical or behavioral characteristics that appear in humans at the time of puberty.

Secondary sexual characters in boys:

(i) Appearance of moustache and beard.

(ii) Appearance of chest hair.

(iii) Growth of hair in genital area and other parts of the skin.

Secondary sexual characters in girls:

(i) Increase in breast size and darkening of the skin of nipples present at the tip of the breasts.

(ii) Growth of hair in genital area and other body parts.

Concept insight: Secondary sexual characters are developed during puberty.

(c) Sex determination in an unbom baby:

The sex of a baby is determined by the type of male gamete that fuses with the female gamete.

All human beings have 23 pairs of chromosomes in their nuclei. Out of these 23 pairs, the last pair is known as the sex chromosome.