NCERT Solutions for Class 8th Science
Chapter 10 – REACHING THE AGE OF ADOLESCENCE
(Complete Downloadable Chapter Solution PDF file is at the bottom of the page)
Q.1 What is the term used for secretions of endocrine glands responsible for changes taking place in the body?
Ans Hormones. Hormones are chemical substances which are secreted from endocrine glands, or endocrine system. They are responsible for changes taking place in the body.
Q.2 Define adolescence.
Ans The period of life, when the body undergoes changes, leading to reproductive maturity, is called adolescence. It begins around the age of 11 and lasts upto 18 or 19 years of age. Since this period covers the ‘teens’ (13 to 18 or 19 years of age), adolescents are also called ‘teenagers’. The period of adolescence varies from person to person.
Q.3 What is menstruation? Explain.
Ans Menstruation (bleeding in women) is the monthly shedding of the thickened lining of the uterus along with its blood vessels and the released egg. It starts with puberty and occurs once in about 28 to 30 days. The ova begin to mature with the onset of puberty. One ovum matures and is released by one of the ovaries once in about 28 to 30 days. During this period, the uterine wall becomes thick and prepares itself to receive the developing fertilised egg. In case there is no fertilisation, the thickened lining of the uterine wall breaks down and goes out of the body along with blood.
Q.4 List changes in the body that take place at puberty.
Ans Changes that take place at puberty:
1. Sudden increase in height.
2. Change in body shape: In boys, shoulders broaden and chest widens whereas in girls, the region below the waist becomes wider.
3. Change in the voice: Girls have a high pitched voice, whereas boys have a deep voice.
4. Secretion of sweat glands and sebaceous glands (oil glands) increases leading to acne or pimples.
5. Development of sex organs: In boys, testes begin to produce sperms whereas in girls, the ovaries enlarge and eggs begin to mature.
6. Secondary sexual characters: Breasts begin to develop in girls and boys begin to grow facial hair. Both develop hair under arms, pubic region etc.
Q.5 Prepare a Table having two columns depicting names of endocrine glands and hormones secreted by them.
Q.6 What are sex hormones? Why are they named so? State their function.
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.
Q.8 Write notes on—
(a) Adam’s apple.
(b) Secondary sexual characters.
(c) Sex determination in the unborn baby.
Ans (a) Adam’s apple – The protruding part of the throat in boys due to the growing voice box or larynx at puberty is called the Adam’s apple. Sometimes the muscles of the growing voice box go out of control and the voice becomes hoarse.
Q.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
Q.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?