NCERT Solutions for Class 8 Science Reaching the Age of Adolescence

Class–VIII Science NCERT SOLUTION

Ch-10 Reaching the age of Adolescence

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

Ans. The term used for secretion of endocrine glands is hormones, which is responsible for various changes taking place in the body.

2. Define adolescence.

Ans. The period of life when the body undergoes changes, leading to reproductive maturity, is called adolescence.

NCERT Solutions for Class 8 Science Reaching the Age of Adolescence

3. What is menstruation? Explain.

Ans. The cyclic flow of blood and mucus along with inner lining of uterus in case of not fertilisation of egg from the female body is called menstruation. Each month uterus prepares itself to receive the fertilized egg. If fertilisation do not occurs the inner ling breaks away and comes out through vagina for 3-5 days.

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

Ans. The onset of puberty brings about:

(i) Growth of the reproductive organs which begin to function.

(ii) Hair growth at various places of the body. Breasts develop in girls and facial hairs appear in boys.

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

NCERT Solutions for Class 8 Science Reaching the Age of Adolescence

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

Ans.

NCERT Solutions for Class 8 Science Reaching the Age of Adolescence

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

Ans. Testes and ovaries secrete sex hormone. This is secreted by endocrine glands. These hormones are responsible for the male and female secondary sexual characters. That is why these hormones are called sex-hormones. Further, the sex-hormone are under the control of hormones from pituitary glands.

NCERT Solutions for Class 8 Science Reaching the Age of Adolescence

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 start.

(ii) Breast start developing

(iii) Body weight increases

(iv) Height increases.

(c) The right meal for adolescents consist of 

(i) Chips, noodles, coke.

(ii) Chapatti, dal, vegetables.

(iii) Rice, noodles and burger.

(iv) Vegetables cutlets, chips and lemon drink.

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

(b) (i) menstruation starts.

(c) (ii) Chapatti, dal, vegetables.

NCERT Solutions for Class 8 Science Reaching the Age of Adolescence

8. Write notes on-

(a) Adam’s apple.

(b) Secondary sexual charecters.

(c) Sex determination in unborn baby.

Ans. (i) Adam’s apple- At puberty, the voice box or the larynx begins to grow. The growing voice box in boys can be seen a protruding part of the throat called Adam’s apple.

(ii) Secondary sexual characters- Those changes that take place at puberty in boys and girls are called secondary sexual characters. In includes increase in size of breast in girls and pubic hairs around genital organ in girls. In boys facial hair and cracking of voice are secondary sexual features.

(iii) Sex determination in the unborn baby- Human beings have 23 pairs of chromosome. One pair of male (XY) and one pair of chromosome in female (XX) are called sex chromosome. Male produce two types of gametes half containing X chromosome and half containing Y chromosome. When the sperm containing Y chromosome fuse with egg the sex of baby is male and when X chromosome containing sperm fertilse the egg the sex of baby is female.

NCERT Solutions for Class 8 Science Reaching the Age of Adolescence

9. Word game: use the clues to work out the words.

Across

3. Protruding voice box in boys

4. Glands without ducts

7. Endocrine gland attached to brain

8. Secretion of endocrine glands

9. Pancreatic hormone

10. Female hormone

Down

1. Male hormone

2. Secretes thyroxin

3. Another term for teenage

5. Hormone reaches here through blood stream

7. Term for changes at adolescence

Ans.

NCERT Solutions for Class 8 Science Reaching the Age of Adolescence

10. The table below shows the data on likely height of boys and girls as they grow in age. Draw graphs showing height and age for both boys and girls on the same graph paper. What conclusions can be drawn from these graphs?

Ans.

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