NCERT Solutions Class 8 Science Chapter 10 Reaching the Age of Adolescence

NCERT Solutions Class 8 Science 

The NCERT Solutions in English Language for Class 8 Science Chapter – 10 (Reaching the Age of Adolescence) has been provided here to help the students in solving the questions from this exercise.

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?
Answer – Hormones is the term used for chemical secretion of endocrine glands responsible for changes taking in the body. Hormones are chemical messengers that transport signals from one cell (or gland) to another cell (or gland).

 2. Define adolescence.
Answer – Adolescence is a period of life when body undergoes changes leading to reproductive maturity. It is the Period between 11 to 19 years There are also other physical and emotional changes that occur during this period.

3. What is menstruation? Explain.
Answer – Menstruation is a process in which blood and mucous flows out every month through the vagina. Menstruation usually lasts for 3 to 5 days in human females. The frequency of menstrual cycle in human females is once in a month if egg is not fertilized.

4. List changes in the body that take place at puberty.
Answer – The changes in the body of puberty are:

• Sudden increase in height.
• The bones of arms and legs elongate and make a person tall.
• Growing of hair at different parts of body.
• The voice of a boy gets hoarsed.
• Development of sex organs.
• Growth of moustaches and beards in the boys.

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

6. What are sex hormones? Why are they named so? State their function.
Answer – The chemical substances produced by the sex organs are called sex hormones. For example, in females, the sex hormone produced by the ovary is called oestrogen and in males, the sex hormone produced by the testis is called testosterone. Some of the functions performed by the sex hormones:
Oestrogen – This hormone is responsible for the development of secondary sexual characteristics in females, like enlargement of breasts, development of female reproductive organs, etc.
Testosterone – This hormone develops secondary sex characteristics in boys, such as the growth of beard, the voice becoming hoarse, the development of the 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.

8. 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 in the throat is called Adam’s apple. It is the enlarged voice box or larynx. It makes the voice of boys coarse.

(b) Secondary sexual characters – The characters which help to distinguish the male from female are called secondary sexual characters. The characters like hair on chest under arms, development of breast, beard and moustaches are called secondary sexual characters.

(c) Sex determination in the unborn baby – The sex of unborn baby is determined by the sex chromosomes. An unfertilized egg always has X chromosomes. Sperms are of two types. One contains X chromosomes and the other contains Y chromosomes. If sperm contributes a Y chromosome to the egg at fertilisation, the zygote would develope into male child. If a sperm containing X chromosome fertilises the egg, the zygote would develop into a female.

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 thyroxine
3. Another term for teenage
5. Hormone reaches here through blood stream
6. Voice box
7. Term for changes at adolescence

Answer –

10. The table below 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 –