Science class 8 Chapter 10 – Reaching the age of adolescence NCERT Exercise solution (Question-Answer) provided here. There are Total 10 Questions are in this chapter, their solutions/Answer is provided below.
Science class 8 Chapter 10 – Reaching the age of adolescence NCERT Exercise Question Answer
Q.1. What is the term used for chemical secretions of endocrine glands responsible for changes taking place in the body?
Answer – Harmons are the chemical substances that are secreted by endocrine glands and responsible for changes taking place in the body.
Hormones control the onset of puberty and maturity of reproductive parts.
Q.2. Define adolescence.
Answer – The period of life when the body undergoes changes leading to reproductive maturity is called adolescence.
It begins at the age of 11 and lasts up to 18 or 19 years of age.
There are several changes in the human body during adolescence-
~Boys and girls have become capable of reproduction.
~Boys and girls develop secondary sexual characters.
It is one of the most rapid phases.
It is that time in which humans can learn to manage emotions, relationships, can develop knowledge and skills, etc.
Q.3. What is menstruation? Explain.
Answer – We know that if there were fertilization takes place, this result in pregnancy. But, if there were no fertilization occur the released egg, and the thickened lining of the uterus along with its blood vessels are shed off. This causes bleeding in a woman and it is called menstruation.
Menstruation begins at puberty.
It occurs every month or after 28 to 30 days.
The first period begins between 12 to 15 years of age and this time is known as menarche.
Bleeding usually lasts around 3 to 5 days.
This cycle of menstruation occurs every month in the female body and is known as the menstrual cycle.
It stops at the age of 45 to 50 years and this stoppage of menstruation is termed as menopause.
Q.4. List changes in the body that takes place at puberty.
Answer – Here is the list of changes in the body that takes place at puberty-
A sudden increase in height.
Sex organs developed at puberty.
Change in body shape.
In the female, menstruation starts.
Increased activity of sweat and the sebaceous gland.
In girl, hips become broader and breasts begin to develop.
In boys, the shoulder becomes broader and the chest becomes wider.
In both male and female, the hair grows under armpits, face, hands, and legs.
In boys, the voice box or larynx begins to grow. This growing voice box can be seen as a protruding part of the throat, called Adam’s Apple.
The vocal cord becomes longer and thicker. These changes cause the voice to become hoarse.
Reaching mental, intellectual and emotional maturity.
Q.5. Prepare a Table having two columns depicting names of endocrine glands and hormones secreted by them.
Q.6 What are sex hormones? Why are they named so? State their function.
Answer – Sex hormones are the chemical substances that are produced by sex gland.
Oestrogen is a female sex hormone that is produced by ovary and testosterone is the male sex hormone that is produced by the testis.
Both hormone oestrogen and testosterone are secreted by sex organs which affect the sexual feature of an organism. Hence, they are known as sex hormones.
Functions of sex hormones-
~Oestrogen- It is responsible for the development of secondary sexual characters in females.
ex- Enlargement of breasts, development of female reproductive organs, etc.
~Testosterone- It is responsible for the development of secondary sexual characters in boys.
Example – Growth of beard, the voice becomes hoarse, development of reproductive organ, etc.
Q.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
Answer – (ii) Proper diet is needed for the rapid growth taking place in their body
(b) Reproductive age in women starts when their-
(i) menstruation starts.
(ii) Breasts start developing.
(iii) Body weight increases.
(iv) Height increases.
Answer- (i) Menstruation starts.
(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 – (ii) chapati, dal, vegetables.
Q.8 Write notes on—
(a) Adam’s apple.
(b) Secondary sexual characters.
(c) Sex determination in the unborn baby.
(a) Adam’s apple – In male at puberty, the voice box, or the larynx begins to grow. The growing voice box in boys can be seen as a protruding part of the throat that is called Adam’s apple.
Under the influence of sex hormone, the larynx becomes prominent that results the vocal cords become longer and thicker which cause the voice to become hoarse.
(b) Secondary sexual character-
The feature which helps to distinguish between male and female is known as a secondary sexual character.
Secondary Sexual Characters in girls-
- Growth of hair in the genital area underarms and other body parts.
- Size of breast starts developing and the skin of nipple which is present at the tip of the breasts starts to darkening.
Secondary Sexual Characters in boys-
- Growing to facial hair that is moustaches, and beard.
- Growth of hair in the genital area underarm and other body parts.
- The appearance of chest hair
(c) Sex determination in unborn baby-
The sex of the unborn baby is determined by the type of male gamete which fuses with the female gamete.
All human beings have 23 pair of chromosomes in the nuclei of their cell.
Out of these two chromosomes are sex chromosomes – X and Y.
Female have 23 pair of chromosomes including XX sex chromosomes.
Therefore, female gamete can only have 22 chromosomes and one X chromosome.
Male gamete can have two kinds, one has an X chromosome and other has a Y chromosome.
They have 23 pair of chromosome including XY sex chromosome.
Male gamete – 22+X or 22+ Y
Female gamete – 22+X
So, the sex chromosome of the father determines the sex of the unborn baby. So the father is responsible for the sex of the unborn baby and we all believe that the mother is responsible for the sex of the unborn baby is completely wrong.
Q9. Word game: Use the clues to work out the words.
3. The protruding voice in boys
4. Glands without duct
7. Endocrine gland attached to the brain
8. Secretion of endocrine glands
9. Pancreatic hormone
10. Female hormone
1. Male hormone
2. Secretes thyroxine
3. Another term for teenage
5. Hormone reaches here through the bloodstream.
7. The term for changes at adolescence
Q.10 The table shows the data on likely heights 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?
Answer – From the above graph, we conclude that the boy’s height grows faster than girls till the age of 8 years. After that, from 8 to 16 years girls grows faster. And finally, boys have a usually greater height than girls after the age of 16 years. Both reach at their maximum height at the age of 20.