NCERT Solutions - Reaching the Age of Adolescence, Science, Class 8 Class 8 Notes | EduRev

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Class 8 : NCERT Solutions - Reaching the Age of Adolescence, Science, Class 8 Class 8 Notes | EduRev

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NCERT TEXTBOOK QUESTIONS SOLVED
 

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

Q. 2. Define adolescence.
Ans.
The period of life, when the body undergoes changes, leading to reproductive maturity is called adolescence.
 

Q. 3. What is menstruation? Explain.
Ans.
When the egg produced by ovary does not get fertilised, the released egg and the thickened lining of the uterus along with its blood vessels are shed off. This causes bleeding in women which is called menstruation. Menstruation occurs once in about 28 to 30 days.
 

Q. 4. List the changes in the body that take place at puberty.
Ans.
The changes in the body at puberty are:
(i) Sudden increase in height.
(ii) The bones of arms and legs elongate and make a person tall.
(iii) Growing of hair at different parts of body.
(iv) The voice of a boy gets hoarsed.
(v) Development of sex organs.
(vi) Growth of moustaches and beards in the boys.
(vii) The breast in girls develops and hips become wider whereas in boys shoulders generally broaden. 


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

Endocrine glands

Hormones

  1. Pituitary gland
  2. Ovaries
  3. Testes
  4. Thyroid
  5. Pancreas
  6. Adrenal glands
  1. Growth hormones
  2. Estrogen
  3. Testosterone
  4. Thyroxine
  5. Insulin
  6. Adrenalin
 

Q. 6. What are sex hormones? Why are they named so? State their functions.
Ans.
The hormones which help and control the formation of secondary sexual characters are called sex hormones. They are called sex hormones because they control the sexual activities and help us to distinguish boys from girls.
The sex hormones help to develop the secondary sexual characters. Such as, in boys they control formation of sperms by testes and growth of facial hair. In girls they help to develop breasts, milk secreting glands or mammary glands.
 

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.

 

(b) Reproductive age in women starts when their

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

 

(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.

 

Ans. (a) (ii) proper diet is needed for the rapid growth taking place in their body.
(b) (i) menstruation starts.
(c) (ii) chapati, dal, vegetables.


Q. 8. Write notes on: (a) Adam’s apple
(b) Secondary sexual characters
(c) Sex determination in unborn baby.

Ans. (a) Adam’s apple:
The protruding part of the throat in boys 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  and under arms, development of breast, beard and moustaches are called secondary sexual characters.

(c) Sex determination in 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 develop into male child. If a sperm containing X chromosome fertilises the egg, the zygote would develop into a female child.

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