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SEBA Class 8 Science Chapter 13 Reaching The Age of Adolescence
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Reaching The Age of Adolescence
Chapter: 13
PART – II
EXERCISE
1. What is the term used for secretions of endocrine glands responsible for changes taking place in the body?
Ans: Hormones are secretions of the endocrine glands directly secreted into the bloodstream, and they are translocated to the target site.
2. Define adolescence.
Ans: Adolescence is the phase of life between childhood and adulthood, from ages 10 to 19. It is a unique stage of human development and an important time for laying the foundations of good health. Adolescents experience rapid physical, cognitive and psychosocial growth. During this time, individuals experience puberty, a process involving hormonal changes that lead to reproductive maturity and the development of secondary sexual characteristics.
3. What is menstruation? Explain.
Ans: Menstruation is the monthly process in females in which the inner lining of the uterus along with blood and tissues is shed through the vagina. This happens when fertilisation does not occur. It usually begins between the ages of 10 to 14, marking the start of puberty in girls. Menstruation is a natural part of the reproductive cycle and a sign that a girl’s body is becoming capable of reproduction. The cycle typically lasts about 28 days, and the bleeding phase usually continues for 3 to 7 days.
4. List changes in the body that take place at puberty.
Ans: (i) Voice becomes deeper in boys (Adam’s apple appears).
(ii) Breasts develop in girls.
(iii) Growth in height and weight.
(iv) Oily skin and pimples may appear.
(v) Sex organs become mature.
(vi) Boys start producing sperms, girls start menstruating.
(vii) Growth of hair in armpits and private parts.
5. Prepare a Table having two columns depicting names of endocrine glands and hormones secreted by them.
Ans:
| Endocrine Gland | Hormone Secreted |
| Pituitary gland | Growth hormone |
| Thyroid gland | Thyroxine |
| Pancreas | Insulin |
| Adrenal gland | Adrenaline |
| Testes (in boys) | Testosterone |
| Ovaries (in girls) | Estrogen |
6. What are sex hormones? Why are they named so? State their function.
Ans: Sex hormones are special chemical substances produced by the reproductive organs in boys and girls during puberty. In boys, the testes produce a hormone called testosterone, while in girls, the ovaries produce estrogen. These hormones are known as sex hormones because they are responsible for the physical and biological changes that make a child’s body mature into an adult body capable of reproduction. They help in the development of secondary sexual characteristics. For example, in boys, testosterone causes a deeper voice, growth of facial and body hair, and an increase in muscle mass. In girls, estrogen leads to the development of breasts, widening of hips, and the start of menstruation. These hormones also help the reproductive organs to grow and function properly. Therefore, sex hormones play a very important role in human growth, development, and reproduction.
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, cake.
(ii) Chapati, dal, vegetables.
(iii) Rice, noodles and burger.
(iv) Vegetable cutlets, chips and lemon drink.
Ans: (ii) Chapati, dal, vegetables.
8. Write notes on-
(a) Adam’s apple.
Ans: The Adam’s apple is the protruding part of the throat that becomes visible in boys during puberty. It is formed due to the growth of the voice box (larynx). During adolescence, boys develop a larger larynx than girls, which causes the Adam’s apple to stick out. This growth is also responsible for the deepening of the voice in boys. In contrast, girls have a smaller larynx, so the Adam’s apple is usually not visible in them. Sometimes, during this stage, boys experience voice cracking or hoarseness, but this is temporary and settles down as the voice box muscles adjust.
(b) Secondary sexual characters.
Ans: Secondary sexual characters are the physical features that appear in boys and girls during puberty and help to distinguish males from females. These are different from the primary reproductive organs like testes and ovaries. In boys, these changes include the growth of facial hair such as moustaches and beards, development of chest hair, deepening of the voice, and the appearance of the Adam’s apple due to the enlargement of the voice box. In girls, secondary sexual characters include the development of breasts and the widening of hips. In both boys and girls, hair begins to grow under the arms and in the pubic region. These changes are controlled by hormones. In boys, the testes release the male hormone called testosterone, which is responsible for the development of male secondary sexual characters. In girls, the ovaries release the female hormone called estrogen, which leads to the development of breasts and mammary glands. The production of these hormones is regulated by another hormone secreted by the pituitary gland, an important endocrine gland.
(c) Sex determination in the unborn baby.
Ans: Sex determination in the unborn baby depends on the combination of sex chromosomes it receives from the parents. The mother always provides an X chromosome, while the father can provide either an X or a Y chromosome. If the baby inherits an X chromosome from both parents (XX), the baby will be a girl. If the baby receives an X from the mother and a Y from the father (XY), the baby will be a boy. Thus, the father’s chromosome decides the baby’s sex.
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. Adam’s apple.
4. Endocrine.
7. Pituitary.
8. Hormone.
9. Insulin.
10. Estrogen.
Down:
1. Testosterone.
2. Thyroid.
3. Adolescence.
4. Target organ.
5. Larynx.
6. Puberty.
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