Saturday, 11 June 2016

TEXTBOOK ANSWERS AND SOLUTIONS OF CBSE CLASS VIII SCIENCE Chapter 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?

ANSWER:- Hormones

2)Define adolescence.

ANSWER:-Adolescence is the time period between the beginning of puberty and adulthood. During this period, the body undergoes several changes alongside reproductive maturity.

3)What is menstruation? Explain.

ANSWER:-Menstruation is the process of the shedding of the uterine lining on a regular monthly basis. It begins at puberty and is the reproductive cycle of the female body. Every month, the uterus prepares itself to receive a fertilized egg.
Therefore, the inner lining of the uterus becomes thick and is supplied with blood to nourish the embryo. If the egg is not fertilized, then the lining of the uterus breaks down and gets released in the form of blood through the vagina. This lasts for about two to eight days. This cycle occurs every month and is known as the menstrual cycle.

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



ANSWER:-Changes at puberty:
(i) Sudden increase in height and weight.
(ii) Broadening of shoulders and widening of chest in boys. In girls, the region below waist becomes wider.
(iii) In boys, under the influence of hormones, the larynx becomes prominent, the vocal cords become longer and thicker. These changes cause the voice to become hoarse.
(iv) Appearance of hair in areas such as underarms, face, hands, and legs.
(v)Reproductive organs begin to mature.

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

ANSWER:-
Endocrine gland          Hormones
Testis.                          Testosterone
Ovary                          Oestrogen
Thyroid                       Thyroxin
Adrenal                       Adrenalin
Pancreas.                     Insulin
Pituitary.                     Growth hormone

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

ANSWER: - Sex hormones are chemical substances produced by sex organs. For example, testosterone is the male sex hormone produced by the testis, and oestrogen is the female sex hormone produced by the ovary.
These hormones affect the sexual features of an organism. Hence, they are known as sex hormones.
Functions of sex hormones:
Testosterone: This hormone brings about secondary sex characters in boys such as the growth of a beard, the voice becoming hoarse, development of reproductive organs, etc.
Oestrogen: This hormone is responsible for the development of secondary sexual characters in females such as the enlargement of breasts, development of female reproductive organs, etc.

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.

Q8. Write notes on—
(a) Adam’s apple.
(b) Secondary sexual characters.
(c) Sex determination in the unborn baby.

ANSWER:- a) 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.
b) Secondary Sexual Characters are those characters which distinguish a male from female


c) Sex determination in unborn baby:

All human beings have 23 pairs of chromosomes in the nuclei of their cells. Two chromosomes out of these 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 unfertilised egg always has one X chromosome. But sperms are of two kinds. One kind has an X chromosome, and the other kind has a Y chromosome. When a sperm containing X chromosome fertilises 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 fertilisation, the zygote would develop into a male child. This concludes that the sex chromosomes of the father determine the sex of an unborn baby.


Written By Badal Paul
The author is a passionate blogger, writer and educationalist. This blog is created to ease troubles of the Cbse students. The author holds multiple blogs and the writer of the Novel KALCHAKRA, OOM AND THE CHOSEN FIVE.