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?

Answer: Changes taking place in the body, is due to chemical substances secreted by endocrine glands, which are known as hormones.

2. Define adolescence.

Answer: Time period from puberty to adulthood is called as adolescence. During adolescence, body undergoes various reproductive changes, from the age of 11 years to age of 18 to 20 years. Age of adolescence differs from person to person.

3. What is menstruation? Explain.

Answer: In females, during reproductive phase, ova matures and is released by one of the ovaries, once in 28 or 30 days. At this time walls of the uterus becomes thick, to receive egg. If fertilisation occurs this, development of zygote starts. In absence of fertilization, thick lining of uterus breaks and released egg along with blood is shed off from the uterus. This causes bleeding in women called as menstruation. This cycle occurs every month and is called as menstrual cycle.

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

Answer: Following are the changes observed during puberty-

• Increase in height and weight.
• Shoulders are broden and chest is widen in boys. Vocal cords become longer and thicker causing voice to become hoarse.
• In girls region below the waist becomes wider and development of breasts is observed.
• Appearance of hairs of face, underarms, etc.
• Acne is mostly observed during puberty due to excess secretion of oil.
• Development of testis causes production of sperms in males and development of ovaries causes production of eggs and ova in females.

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

Answer:

Endocrine Glands	Hormones
Testis	Testosterone
Ovaries	Oestrogen
Pancreas	Insulin
Thyroid	Thyroxin
Adrenal	Adrenalin
Pituitary	Growth hormone

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

Answer: Sex hormones are produced from sex organs in human body. In males, testis produces testosterone and in females ovaries produces oestrogen. These hormones are responsible for sexual characters and thus are known as sex hormones. Testosterone is responsible for secondary sexual characters like growth of beard, change in voice, development of reproductive organs in boys. Oestrogen is responsible for secondary sexual characters like enlargement of breast, development of reproductive organs in girls.

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.

Answer: In males during puberty, larynx grows larger and is seen as protruding part of the throat. This part is known as adam’s apple. Under the influence of sex hormones, vocal cords becomes thick and longer which makes the voice hoarse. In females, larynx is small in size and is hardly visible. Therefore, females have high pitch and males have low pitch.

(b) Secondary sexual characters.

Answer: Secondary sexual characters show physical or behavioural changes at the time of puberty that shows difference between male and female.

• Secondary sexual characters in males –
  • Appearance of moustaches and beard
  • Hair growth on chest
  • Hair growth in genital areas and other parts
• Secondary sexual characters in females –
  • Enlargement of breasts
  • Hair growth in genital areas and other parts

(c) Sex determination in the unborn baby.

Answer: In humans, 23 pair of chromosomes are present out of which one pair is sex chromosomes. In males 23rd pair of chromosome is XY and in females 23rd pair of chromosome is XX. As female provide only X chromosomes, sex of baby is determined with the help of male chromosome. If X chromosome of female fuses with X chromosome of male then child will be girl child. If X chromosome of female fuses with Y chromosome of male then child is boy.

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:

• Across 3. Adam’s apple 4. Endocrine 7. Pituitary 8. hormones 9. insulin 10. estrogen
• Down 1. testosterone 2. thyroid 3. Adolescence 5. Target site 6. Larynx 7. Puberty

Check other lessons NCERT Solutions for Class 8

Download free NCERT textbook class 8 Science – Chapter 8 Cell Structure and Functions