Science STD 8 Chapter 7: Reaching the Age of Adolescence - Exercises
1. What is the term used for chemical secretions of endocrine glands responsible for changes taking place in the body?
The term used for chemical secretions of endocrine glands is **hormones**.
2. Define adolescence.
Adolescence is the period of life when the human body undergoes changes, leading to reproductive maturity. This period generally begins around the age of 11 and lasts up to 18 or 19 years of age. Adolescents are also called 'teenagers'.
3. What is menstruation? Explain.
Menstruation is the shedding of the uterine lining in females. It occurs approximately once every 28 to 30 days. If the egg released by the ovary is not fertilised, the thickened lining of the uterus and its blood vessels are shed off, causing bleeding in women. The first menstrual flow begins at puberty and is called menarche. The cessation of menstruation, which typically happens between the ages of 45 and 50, is called menopause.
4. List changes in the body that take place at puberty.
The changes in the body that take place at puberty include:
- Increase in height.
- Change in body shape (shoulders broaden in boys, hip region widens in girls).
- Voice change (voice box or larynx grows, leading to a deeper voice in boys).
- Increased activity of sweat and sebaceous glands, often leading to acne and pimples.
- Development of sex organs, and the production of gametes (sperms and ova) begins.
- Appearance of secondary sexual characters like facial hair in boys and breast development in girls.
- Reaching mental, intellectual, and emotional maturity.
5. Prepare a Table having two columns depicting names of endocrine glands and hormones secreted by them.
| Endocrine Gland | Hormone Secreted |
|---|---|
| Pituitary gland | Growth hormone, hormones that stimulate other glands |
| Testes | Testosterone |
| Ovaries | Estrogen |
| Thyroid gland | Thyroxine |
| Pancreas | Insulin |
| Adrenal gland | Adrenalin |
6. What are sex hormones? Why are they named so? State their function.
Sex hormones are chemical substances produced by the testes in males (testosterone) and the ovaries in females (estrogen). They are named sex hormones because they control the development of secondary sexual characters that help to distinguish males from females. Their main function is to initiate and control the changes that occur during puberty, leading to reproductive maturity. For example, testosterone causes the growth of facial hair and a deeper voice in boys, while estrogen causes breast development in girls.
7. Choose the correct option.
- (a) Adolescents should be careful about what they eat, because
- proper diet develops their brains.
- proper diet is needed for the rapid growth taking place in their body.
- adolescents feel hungry all the time.
- taste buds are well developed in teenagers.
- (b) Reproductive age in women starts when their
- menstruation starts.
- breasts start developing.
- body weight increases.
- height increases.
- (c) The right meal for adolescents consists of
- chips, noodles, coke.
- chapati, dal, vegetables.
- rice, noodles and burger.
- vegetable cutlets, chips and lemon drink.
8. Write notes on-
- (a) Adam's apple.
Adam's apple is the common name for the larynx or voice box, which grows larger in boys during puberty. This growth can be seen as a protruding part of the throat. The enlargement of the voice box causes the voice to become deeper or, at times, hoarse. In girls, the larynx is much smaller and is not visible from the outside.
- (b) Secondary sexual characters.
Secondary sexual characters are the features that help to distinguish the male from the female, but are not directly involved in reproduction. These changes appear during puberty and are controlled by sex hormones. In boys, these include the growth of facial hair, a deeper voice, and broader shoulders. In girls, they include the development of breasts and a wider region below the waist.
- (c) Sex determination in the unborn baby.
The sex of an unborn baby is determined at the time of fertilisation by the sex chromosomes inherited from the parents. A female has two X chromosomes (XX), while a male has one X and one Y chromosome (XY). The egg always contains an X chromosome. A sperm, however, can have either an X or a Y chromosome. If a sperm with an X chromosome fertilises the egg, the child will be a girl (XX). If a sperm with a Y chromosome fertilises the egg, the child will be a boy (XY). Therefore, the male's sperm determines the sex of the baby.
9. Word game: Use the clues to work out the words.
Across
3. Protruding voice box in boys - **ADAM'S 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**
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?
A graph would be plotted with Age on the X-axis and Height on the Y-axis. The data for both boys and girls would be plotted as two separate lines on the same graph.
Conclusions:
- In the early years, the height of both boys and girls increases at a similar rate.
- Girls grow faster during the initial period of adolescence but reach their maximum height earlier than boys.
- Boys continue to grow and reach their maximum height later than girls.
- By the age of 16-17, most individuals have reached their full height, with the growth rate slowing down significantly after that.
Suggested Activities and Projects
1. Find out from your elder relatives about their awareness of the legal status of early marriage. You yourself may get information on it from your teacher, parents, a doctor or the internet. Write a two-minute speech explaining why early marriage is not good for the couple.
Outline: This activity focuses on understanding the issue of early marriage. You would research the legal age for marriage and the reasons behind it. The speech would highlight that early marriage can lead to health problems for both the mother and the child, and it can also curtail a young woman's educational and employment opportunities. The speech would advocate for waiting until the legal age to marry to ensure physical and mental maturity for both partners.
2. Collect newspaper cuttings and information in magazines about HIV/ AIDS. Write a one page article of 15 to 20 sentences on HIV/AIDS.
Outline: This project involves researching and raising awareness about HIV/AIDS. The article would explain that HIV is a dangerous virus that can be transmitted through shared syringes, sexual contact, and from an infected mother to her infant. The article would also dispel myths and promote the importance of safe practices to prevent the spread of the virus.
3. In our country, according to 2011 census, there are 940 adolescent females for every 1000 males. Find out. (a) the concerns of the community regarding this low ratio. Remember that the chance of having a boy or a girl is equal. (b) what amniocentesis is and how useful this technique is. Why is its use for identification of sex of the unborn child banned in India? Put your ideas together and write a short note on the importance of knowing facts about reproduction.
Outline: This activity is a research project on gender disparity and its social implications. You would research the low female-to-male ratio and the societal concerns associated with it. You would also research amniocentesis, a technique used to detect genetic and chromosomal abnormalities in a foetus. You would learn that its use for sex determination is banned in India to prevent female foeticide. The note would highlight the importance of understanding the facts of reproduction to counter such social issues and prejudices.