Chapter 10: Reaching the age of Adolescence 

Extra Internal Question and Answer:

Question: What are sex hormones? Name the sex hormones present in males and females.

Answer: Sex hormones are chemical substances produced by the reproductive organs that control the changes at puberty and help in reproduction. In males, the sex hormone is testosterone, produced by testes. In females, the sex hormones are oestrogen and progesterone, produced by ovaries.

Question: Which organs produce sex hormones in the human body?

Answer: Sex hormones are produced by the reproductive organs. In males, the testes produce testosterone. In females, the ovaries produce oestrogen and progesterone.

Question: State one function of testosterone.

Answer: Testosterone is a male sex hormone produced in the testes. One important function of testosterone is that it helps in the production of sperms in males.

Question: State one function of oestrogen.

Answer: Oestrogen is a female sex hormone. One important function of oestrogen is that it helps in the development of female secondary sexual characteristics such as development of breasts and changes in body shape during puberty.

Question: What role do sex hormones play in puberty?

Answer: Sex hormones play an important role in puberty by bringing changes in the body. They help in the development of reproductive organs and cause secondary sexual characters like change in voice, growth of hair in new places, and body shape changes in boys and girls.

Question: How is the sex of the baby determined?

Answer: The sex of the baby is determined by the chromosomes from the father. The mother has XX chromosomes, while the father has XY chromosomes. If an X-carrying sperm fertilises the egg, the baby is a girl (XX). If a Y-carrying sperm fertilises the egg, the baby is a boy (XY).

Question: What is a target site? How do hormones act on their target sites? Give one example of a hormone and its target site.

Answer: A target site is the specific organ or tissue on which a particular hormone acts. Hormones are chemical messengers and they reach their target sites through blood and produce specific effects only there. For example, insulin acts on the liver and muscle cells to control the level of glucose in the blood.

Question: A boy is 9 years old and 120 cm tall. What will be his likely height at the end of growth period?

Answer: The boy’s likely height at the end of growth period can be estimated as:

  

So, his probable adult height will be about 160 cm.

Question: If a boy is 10 years old and 140 cm tall, what may be his final height?

Answer: The boy’s likely height at the end of growth period can be estimated as:

  

So, his likely final height may be about 187 cm.

Question: What is adolescence? What is the age range of adolescence?

Answer: Adolescence is the period of life when a child changes into an adult and the body undergoes many physical and mental changes. It is the transition stage between childhood and adulthood. The age range of adolescence is usually from 11 years to 19 years.

Question: What is puberty? What changes occur during puberty?

Answer: Puberty is the stage in which a child’s body changes into an adult body and becomes capable of reproduction. During puberty, rapid physical growth takes place, and secondary sexual characteristics develop such as change in voice, growth of hair in armpits and pubic region, and development of reproductive organs.

Question: Why is adolescence called a transitional stage?

Answer: Adolescence is called a transitional stage because it is the period when a child changes into an adult. During this time, rapid physical, mental and emotional changes take place, and the body becomes capable of reproduction.

Question: What is menarche? At what age does menarche usually occur?

Answer: Menarche is the first menstrual flow in a girl. It marks the beginning of the reproductive phase. It usually occurs at the age of about 10 to 12 years during puberty.

Question: What is menopause? At what age does menopause usually occur?

Answer: Menopause is the stage in a woman’s life when menstruation stops permanently. It marks the end of the reproductive phase. Menopause usually occurs between 45 to 50 years of age.

Question:How is menopause different from menarche?

Answer: Menarche is the beginning of menstruation in girls at puberty, marking the start of reproductive life. Menopause is the permanent stopping of menstruation in women, marking the end of reproductive life.

Exercises

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

Answer: The chemical secretions of endocrine glands that are responsible for changes in the body are called hormones. They are released directly into the blood and control various body functions like growth, development, and metabolism.
2. Define adolescence.

Answer: The period of life, when the body undergoes changes, leading to reproductive maturity, is called adolescence. Adolescence begins around the age of 11 and lasts upto 18 or 19 years of age.
3. What is menstruation? Explain.

Answer: Menstruation is the monthly process in females in which an ovum (egg) is released from one of the ovaries about once in 28 to 30 days. During this period, the uterus wall becomes thick to prepare for pregnancy. If fertilisation does not occur, the egg and the thickened lining of the uterus, along with its blood vessels, are shed through the vagina. This results in bleeding, which is called menstruation. It starts at puberty and the first menstrual flow is called menarche.
4. List changes in the body that take place at puberty.

Answer: At puberty, several changes take place in the body. The body grows faster and height increases. In boys, shoulders become broader and muscles develop more prominently. In girls, the region below the waist becomes wider. The body shape of boys and girls starts becoming different from each other due to growth changes. These physical changes show that a person has entered adolescence.

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

Answer: The table showing endocrine glands and the hormones secreted by them:

Endocrine Gland	Hormone Secreted
Pituitary gland	Growth hormone
Thyroid gland	Thyroxine
Adrenal glands	Adrenaline
Pancreas	Insulin
Testes	Testosterone
Ovaries	Oestrogen

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

Answer: Sex hormones are special chemical substances produced by the testes in males and ovaries in females. They are called sex hormones because they control the development of male and female reproductive organs and also bring changes at puberty. In males, testosterone is the main sex hormone, while in females, oestrogen and progesterone are the main hormones. These hormones help in the production of sperms and eggs and also control secondary sexual characteristics such as change in voice, body shape and hair growth.

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.

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

[ Adolescents should be careful about their food because their body grows very fast during this stage and needs a balanced and nutritious diet.]

(b) Reproductive age in women starts when their
(i) menstruation starts.
(ii) breasts start developing.
(iii) body weight increases.
(iv) height increases.

Answer: (i) menstruation starts.

[ Reproductive age in women begins at puberty when menstruation starts, meaning the ovaries start releasing eggs regularly.]

(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.

Answer: (ii) chapati, dal, vegetables.

[ A right meal for adolescents should be balanced and nutritious, including carbohydrates, proteins, vitamins and minerals for proper growth and good health.]

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

Answer: (a) Adam’s apple is the protruding part seen in the throat of boys. It is formed due to the growth of the voice box or larynx during puberty. Boys develop a larger voice box, so it becomes visible as a bulge in the throat. In girls, the voice box remains small and is not visible from outside.

(b) Secondary sexual characters are features that develop at puberty and help to distinguish males from females. In girls, breasts begin to develop. In boys, facial hair like moustache and beard starts growing. Hair also grows under the arms and in the pubic region in both boys and girls.

(c) Sex determination in the unborn baby is decided by the chromosomes present in the sperm of the father. The mother has only X chromosomes, while the father has both X and Y chromosomes. If the sperm carrying X fertilises the egg, the baby will be a girl. If the sperm carrying Y fertilises the egg, the baby will be a boy.

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

Answer: 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 ----- Hormones .
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 .

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?

Answer: Answer: The graphs show that girls grow faster initially , overtaking boys around age 12. However, boys grow for a longer duration, eventually reaching a taller average height (173 cm) than girls (165 cm) by age 20. Both start at the same height at birth .