NCERT Class 8 Science Chapter 10 Solution
Brief Information: This post contains the solution for Chapter 10 Reaching the Age of Adolescence of Class 8 of the CBSE and Gujarat Board (GSEB) books by GCERT (based on new NCERT).
Q1. What is the term used for secretions of endocrine glands responsible for changes taking place in the body?
Ans. Hormones are secreted from endocrine glands which 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. Adolescence period lasts from age of 11 years to 19 years.
Q.3. What is menstruation? Explain.
Ans. After 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 wall of the uterus becomes thick so as to receive the egg, in case it is fertilised and begins to develop. This results in pregnancy. If fertilisation does not occur, 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.
Q.4. List changes in the body that take place at puberty.
Ans. The human body undergoes several changes during adolescence. These changes mark the onset of puberty. This changes include:
- 1. Sudden increase in height. The bones of the arms and the legs elongate and make a person tall.
- 2. Changes in body Shape occur. In girls, the region below the waist becomes wider. In boys, the muscles of the body grow more prominently than in the girls.
- 3. Change in voice occur. The voice box or the larynx begins to grow. Adams’ apple, a protruding part of the throat becomes visible in boys. Girls develop a high pitched voice, whereas boys develop a deep voice.
- 4. The secretion of sweat glands and sebaceous glands (oil glands) increases. This may result into acne and pimples on the face.
- 5. Development of sex organs occur. Male sex organs like the testes and penis develop completely. The testes begin to produce sperms. In girls, the ovaries enlarge and eggs begin to mature. Ovaries start releasing mature eggs.
- 6. Person becomes mentally and emotionally mature.
- 7. Secondary sexual character such as breasts in girls and facial hairs (i.e mustache and beard) in boys begin to develop.
- 8. Individual become capable of reproduction.
Q.5. Prepare a table having two columns depicting names of endocrine glands and hormones secreted by them.
Endocrine glands | Hormones |
| 1. Pituitary gland | Growth hormones, Oxytocin, Prolactin |
| 2. Ovaries | Estrogen, Progesterone |
| 3. Testes | Testosterone |
| 4. Thyroid | Thyroxine |
| 5. Pancreas | Insulin, Glucagon |
| 6. Adrenal glands | Adrenaline, Cortisol |
Q.6. What are sex hormones? Why are they named so? State their function.
Ans. The Sex hormones are the hormones released from testes in male and ovaries in female. These hormones are responsible for development of secondary sex character in boys and girls.
A.) Male Sex Hormone: It is called Testosterone. It results in development of second sexual characters like mustache and beard. They begin formation of sperms.
B.) Female Sex Hormone: It is called Estrogen. They promote development of breasts. They play vital role during pregnancy.
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.
Ans. (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.
Ans. (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.
Ans. (ii) chapati, dal, vegetables.
Q.8. Write notes on:
(a) Adam’s apple
(b) Secondary sexual characters.
(c) Sex determination in the unborn baby.
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
Ans.
Across
3. Protruding voice box in boys – Adams Apple
4. Glands without ducts – Endocrine
7. Endocrine gland attached to brain – Pituitary
8. Secretion of endocrine glands – Hormone
9. Pancreatic hormone – Insulin
10. Female hormone – Estrogen
Down
1. Male hormone – Testosterone
2. Secretes thyroxine – Thyroid
3. Another term for teenage – Adolescence
5. Hormone reaches here through blood stream – Target Site
6. Voice box – Larynx
7. Term for changes at adolescence – Puberty
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?
Ans. At birth the height of boys and girls are same. Thereafter, the height of boys increase more compared to girls in period 0 – 8 years. From between age of 8 – 16, the height of girl increase more than girl. By age of 20 years both boys and girls reach their maximum height but the height of boys is greater than girls.