Class 8 Science

Age of Adolescence

NCERT Solution

Question 1: What is the term used for secretions of endocrine glands responsible for changes taking place in the body?

Answer: Hormone

Question 2: Define adolescence.

Answer: Adolescences is the period of life when many changes take place in the body; leading to reproductive maturity.

Question 3: What is menstruation? Explain.

Answer: In females, one egg is released by either of the ovaries during each month. After that, the uterus develops a thickening to support a foetus to prepare for a possible pregnancy. If fertilization does not take place; egg and thickening in uterus are discarded in small fragments. This results in bleeding through the vagina for some days. The bleeding (through vagina) at the end of menstrual cycle is called menstruation.

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

Answer: Following changes take place in the body during puberty:

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

Answer:

Endocrine GlandHormone
PituitaryGrowth hormone
ThyroidThyroxin
PancreasInsulin
AdrenalAdrenalin

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

Answer: Hormones which influence the functions of gonads and facilitate appearance of secondary sexual characters are called sex hormones. Testosterone and estrogen are the main sex hormones. In boys, testis secretes the hormone testosterone. This hormone is responsible for many changes in boys. In girls, ovaries secrete the hormone estrogen. This is responsible for development of breasts.

Multiple Choice Questions:

Question 1: Adolescents should be careful about what they eat, because

  1. Proper diet develops their brains.
  2. Proper diet is needed for the rapid growth taking place in their body.
  3. Adolescents feel hungry all the time.
  4. Taste buds are well developed in teenagers.

    Answer: (b) Proper diet is needed for the rapid growth taking place in their body.

Question 2: Reproductive age in women starts when their

  1. Menstruation starts
  2. Breasts start developing
  3. Body weight increases
  4. Height increases

    Answer: (a) Menstruation starts

Question 3: The right meal for adolescents consists of

  1. Chips, noodles, coke
  2. Chapatti, dal, vegetables
  3. Rice, noodles and burger
  4. Vegetable cutlets, chips and lemon drink

    Answer: (b) Chapatti, dal, vegetables

Write notes on following:

Question 1: Adam's Apple

Answer: Enlargement of voice box is apparent as a prominent protrusion in the neck. This protrusion is called Adam’s apple.

Question 2: Secondary sexual characters

Answer: Characters which help in distinguishing a male from a female are called secondary sexual characters.

Question 3: Sex determination in the unborn baby.

Answer: Gametes in humans have 23 chromosomes, i.e. half the number in somatic cells. So, a sperm may have X or Y chromosome as 23rd chromosome. But, an ovum has X chromosome as 23rd chromosome.