NCERT Solutions for Class 8 Science Chapter 10 - Reaching The Age of Adolescence

Boys and girls undergo certain changes after they enter their teens. Some boys start getting facial hair and their voice also changes. Many boys and girls start growing noticeably taller as well. These are because of hormonal changes that occur at this time. This stage of life is called adolescence.

Students will learn about the physical and mental changes that occur in the body on reaching adolescence. They will learn in detail about hormones and glands like Thyroid, endocrine and pituitary. They will gain insights into how to maintain personal hygiene and develop healthy habits during this time.

Download PDF of NCERT Solutions for Class 8 Science Chapter 10 - Reaching The Age of Adolescence

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

The endocrine system consists of special organs that pour their secretions called hormones into the blood and the blood carries them to different cells and tissues of the body.

2. Define adolescence.

Adolescenec is the specific time frame for the organisms which starts from puberty and ends in adulthood. It marks the starting of adulthood. The body becomes matures and changes in various aspects to achieve complete sexual development. The time for adolescence is between the age of 11 and 18. However, this may differ from one person to another.

3. What is menstruation? Explain.

Menstruation is process in which the uterus of female reproductive tract starts to shed its inner lining. This happens every month and forms the reproductive cycle of female organism. The lining of the uterus starts to become thick after fertilisation to support embedding of the embryo.

However, when the egg is not fertilised the lining of the uterus breaks and falls of through the opening of the female reproductive organ, vagina. This lining contains blood and pieces of uterus lining. The menstruation lasts for about 2-5 days and this periodic event is called menstrual cycle.

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

Puberty is marked by several changes in the body.

◉ After puberty the total mass of the body and height increases.
◉ The body starts to develop hair in places like arms, legs, armpits, In males the hair also develops on face and chest.
◉ The shoulder and chest broadens in males and in females the waist grows in width and becomes wider.
◉ The ovaries also become larger and produces eggs monthly. The sperms start to form in testis in males.
◉ The laryngeal region in males develop and the vocal cord becomes thicker so males develop a characteristic hoarse and deep voice.
◉ Teenagers in their adolescence also start to develop acne as the oil glands start producing oil in the skin.

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

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

Sex hormones are the produced from the reproductive or sexual organs of males and females. Hence, the name sex hormones.

The ovaries produce hormone called oestrogen and males produce testosterone. These hormones are responsible for the development and maturation of the reproductive organs.

7. Choose 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.


Correct answer: (ii)

The adolescents require diet containing proper nutrition because their body is rapidly developing and maturing. This needs more energy and all the essential nutrients.

(b) Reproductive age in women starts when their


(i) menstruation starts.
(ii) breasts start developing.
(iii) body weight increases.
(iv) height increases.


Correct answer: (i)

Starting of menstruation marks the beginning of reproductive age in women. During this stage the uterus starts to prepare for fertilisation and the body reacts to presence and absence of fertilisation.

(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.

Correct answer: (ii)

The right mean for teenagers include food rich in proteins like dal, carbohydrates like chapati and vitamins and minerals that are present in vegetables. All these nutrients provide essential nutrients to the body.

8. Write notes on-

Adam’s apple:

It is present in human males where the part of the throat called larynx becomes enlarged during puberty and can be seen prominently in the neck. It is a protruding part and contains thick and long vocal cords.

These features make the voice more deep and hoarse in males than in females. This prominent bulge is called adam’s apple. In females the larynx is not that enlarged and so the voice of females is high pitched.

Secondary sexual characters:

The features that develop apart from the primary sexual characters like maturation of ovaries and testis are called secondary sexual characters. These develop at the time of puberty and are different in males and females.

In males the development of hair on chest, pubic region, hoarse and deep voice are part of secondary sexual characters.

In females the development of breasts, enlargement of waist and development of hair on genitals are secondary sexual characters.

Sex determination in unborn baby:

The sex in an organisms is determined by the presence of sex chromosomes. The male child contain X and Y chromosomes and females contain X and X chromosomes. The sperm may contain either X or Y chromosome and ovum contains only X chromosomes. So when X of sperm meets X of ovum it makes girl child and when Y of sperm meets X of ovum it forms male child.

9. Use the clues to work out the words.

Across

3. Protruding voice box in boys: Adam’s apple
4. Glands without ducts: Endocrine
7. Endocrine gland attached to brain: Pituitary
8. Secretion of endocrine glands: Hormones
9. Pancreatic hormone: Insulin
10. Female hormone: Oestrogen

Down

1. Male hormone: Testosterone
2. Secretes thyroxine: Thyroid
3. Another term for teenage: Adolescence
5. Hormone reaches here through blood stream: Target site
6. Voice box: Larynx
7. Term for changes at adolescence: Puberty

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