Reaching the Age of Adolescence
Welcome to HSLC Guru! In this article, we present a complete guide to Class 8 General Science Chapter 13 — Reaching the Age of Adolescence, prepared in accordance with the latest ASSEB (Assam State School Education Board) syllabus. This chapter explains the biological and emotional changes that occur during adolescence, the role of hormones, the menstrual cycle, sex determination, reproductive health, and the importance of a healthy lifestyle. The notes include a clear summary, all textbook questions and answers, additional MCQs, fill in the blanks, true or false statements, and a glossary to help students score better in their school examinations.
Summary
Adolescence is the period of life when the body undergoes several changes leading to reproductive maturity. It begins around the age of 11 and continues up to 18 or 19 years. Since adolescents are also called teenagers, this stage covers the years 13 to 19. Adolescence ends when an individual becomes capable of reproduction. The specific period during which sexual maturity is attained is called puberty. During this time, the most noticeable physical change is a sudden increase in height, caused by the elongation of bones in the arms and legs. Body shape also changes — in girls, the region below the waist becomes wider, while in boys, the shoulders broaden and chest muscles develop. The voice changes due to the growth of the voice box (larynx); boys often develop a hoarse voice and a visible Adam’s apple, whereas girls develop a higher-pitched voice. Increased activity of sweat glands and sebaceous (oil) glands may cause acne and pimples on the face.
The most important change at puberty is sexual maturation. The reproductive organs (testes in boys, ovaries in girls) develop and start producing gametes — sperms in males and ova (eggs) in females. New features such as the development of breasts in girls and growth of facial hair (moustache and beard) in boys appear at this time. These features that help to distinguish males from females are called secondary sexual characters. All these changes are controlled by chemical substances called hormones, which are secreted by special organs called endocrine glands. The pituitary gland, located in the brain, is the master gland that secretes hormones which stimulate the testes to produce testosterone and the ovaries to produce oestrogen. Testosterone causes the male secondary sexual characters, while oestrogen is responsible for the development of the female secondary sexual characters.
In females, the ovaries release a mature ovum once every 28 days. If the egg is fertilised, it develops into an embryo; if not, the thickened uterine lining breaks down and is shed along with blood and tissue. This monthly process is called menstruation or the menstrual cycle. The first menstrual flow is called menarche, and the stoppage of menstruation around 45 to 50 years of age is called menopause. The years during which a woman can produce children are called the reproductive phase of life. The sex of a child is determined at the time of fertilisation by sex chromosomes — females have XX chromosomes and males have XY chromosomes. If the sperm carrying the X chromosome fertilises the egg, a girl child (XX) is born; if the Y-bearing sperm fertilises the egg, a boy child (XY) is born. Therefore, the father’s sperm decides the sex of the baby, not the mother.
Apart from sex hormones, several other hormones regulate body functions. Thyroxine (from the thyroid gland) controls metabolism; insulin (from the pancreas) controls blood sugar; adrenaline (from adrenal glands) helps us cope with stress; and growth hormone (from pituitary) controls overall body growth. Reproductive health means the proper care of one’s body during adolescence. Adolescents need a balanced diet rich in proteins, vitamins, minerals, and iron. Indian foods like roti, dal, rice, vegetables, fruits, milk, eggs, and meat provide all required nutrients. Junk food should be avoided. Personal hygiene — daily bathing and changing of clothes — is essential, especially during menstruation. Regular physical exercise keeps the body fit and the mind alert. Adolescents must say NO to drugs, alcohol, and tobacco, as these substances damage health and may lead to addiction. The HIV (Human Immunodeficiency Virus) that causes AIDS can spread through infected needles, contaminated blood, and from an infected mother to her baby; awareness and care can prevent it.
Textbook Question and Answer
1 Mark Questions
Q1. What is adolescence?
Answer: Adolescence is the period of life when the body undergoes changes leading to reproductive maturity, generally between the ages of 11 and 18 or 19 years.
Q2. What is puberty?
Answer: Puberty is the specific period during which an individual attains sexual maturity and becomes capable of reproduction.
Q3. Name the master endocrine gland in the human body.
Answer: The pituitary gland is called the master endocrine gland.
Q4. Name the male sex hormone.
Answer: The male sex hormone is testosterone, secreted by the testes.
Q5. Name the female sex hormone.
Answer: The female sex hormone is oestrogen, secreted by the ovaries.
Q6. What is menarche?
Answer: The first menstrual flow that begins at puberty in girls is called menarche.
Q7. What is menopause?
Answer: The permanent stoppage of menstruation in women, generally between 45 and 50 years of age, is called menopause.
Q8. What are the sex chromosomes in human beings?
Answer: The sex chromosomes in human beings are X and Y. Females have XX and males have XY chromosomes.
Q9. Name the hormone that controls the level of sugar in the blood.
Answer: Insulin, secreted by the pancreas, controls the level of sugar in the blood.
Q10. What is the full form of AIDS?
Answer: AIDS stands for Acquired Immuno Deficiency Syndrome, caused by the HIV virus.
2-3 Marks Questions
Q1. List the changes that take place in the body of boys at puberty.
Answer: The changes in boys at puberty are:
- Sudden increase in height and broadening of shoulders.
- Development of facial hair (moustache and beard).
- Voice becomes hoarse and the Adam’s apple becomes prominent.
- Testes begin to produce sperms.
- Increased activity of sweat and oil glands causing pimples.
Q2. Mention the changes that take place in girls at puberty.
Answer: The changes in girls at puberty are:
- Sudden increase in height; the region below the waist becomes wider.
- Development of breasts and a higher pitched voice.
- Ovaries enlarge and begin to release mature eggs.
- Onset of menstruation (menarche).
- Skin becomes oily; pimples may appear.
Q3. What are secondary sexual characters? Give two examples each in boys and girls.
Answer: The features that help to distinguish males from females but are not directly involved in reproduction are called secondary sexual characters.
- In boys: Growth of facial hair (beard and moustache); deep, hoarse voice.
- In girls: Development of breasts; higher-pitched voice.
Q4. What is the menstrual cycle? Mention its average duration.
Answer: The menstrual cycle is the monthly cycle of changes in the female reproductive system in which the ovary releases an egg, and if it is not fertilised, the thickened lining of the uterus is shed along with blood. The average duration of the menstrual cycle is about 28 days.
Q5. Why are adolescents advised to take a balanced diet?
Answer: During adolescence, the body grows rapidly and many internal changes occur. A balanced diet rich in proteins, carbohydrates, fats, vitamins, minerals, and iron is needed to support this growth, build new tissues, and maintain good health. Iron-rich foods are especially important for girls because of menstrual blood loss.
Q6. Why should adolescents say “NO” to drugs?
Answer: Drugs are harmful chemicals that affect the brain and body. They are addictive — once a person starts taking them, it becomes very difficult to give them up. Drugs damage the liver, kidneys, lungs, and nervous system, and can ruin a person’s health, education, family life, and future. Therefore, adolescents must firmly say NO to drugs, alcohol, and tobacco.
5-6 Marks Questions
Q1. Describe the role of hormones in initiating the changes at puberty.
Answer: Hormones are chemical substances secreted by endocrine glands that control various activities in the body. The changes that occur at puberty are mainly controlled by hormones in the following way:
- The pituitary gland, located at the base of the brain, acts as the master gland and secretes hormones that stimulate the testes in boys and ovaries in girls.
- The testes in males secrete the male sex hormone testosterone, which causes the development of male secondary sexual characters such as facial hair, deep voice, and broad shoulders.
- The ovaries in females secrete the female sex hormone oestrogen, which causes the development of breasts and other female features.
- The pituitary also secretes growth hormone, which is responsible for the sudden increase in height during adolescence.
- Together, these hormones bring about the physical, emotional, and reproductive changes typical of puberty.
Q2. Explain how the sex of a child is determined in human beings.
Answer: The sex of a child is determined at the time of fertilisation by the sex chromosomes inherited from the parents. Human beings have 23 pairs of chromosomes, of which one pair is the sex chromosomes. Females have two similar sex chromosomes, written as XX, while males have one X and one Y chromosome, written as XY.
- The mother’s egg always contains an X chromosome.
- The father’s sperm may contain either an X or a Y chromosome.
- If a sperm carrying an X chromosome fertilises the egg, the child will be XX (a girl).
- If a sperm carrying a Y chromosome fertilises the egg, the child will be XY (a boy).
- Therefore, the sex of the baby is decided by the father’s sperm and not by the mother. It is unscientific to blame the mother for the sex of the child.
Q3. What is reproductive health? Mention the steps necessary for keeping good reproductive health during adolescence.
Answer: Reproductive health means the total well-being — physical, mental, and social — relating to the reproductive system. Good reproductive health during adolescence requires the following steps:
- Balanced diet: Eat plenty of proteins, vitamins, minerals, and iron from foods like milk, eggs, fish, pulses, green vegetables, and fruits. Avoid junk food.
- Personal hygiene: Bathe daily, wear clean clothes, and clean all parts of the body. Girls should change sanitary pads frequently during menstruation.
- Physical exercise: Walking, running, playing outdoor games, and yoga keep the body fit and the mind fresh.
- Adequate sleep and rest: Helps the body grow properly.
- Saying NO to drugs: Avoid alcohol, tobacco, and other addictive drugs.
- Awareness about HIV/AIDS: Avoid use of unsterilised needles and unsafe practices that may spread HIV.
Q4. Name some endocrine glands and the hormones they secrete along with their functions.
Answer: The major endocrine glands and their hormones are listed below:
| Gland | Hormone | Function |
|---|---|---|
| Pituitary | Growth hormone | Controls overall growth of the body |
| Thyroid | Thyroxine | Regulates metabolism |
| Pancreas | Insulin | Controls blood sugar level |
| Adrenal | Adrenaline | Helps the body cope with stress and emergencies |
| Testes | Testosterone | Develops male secondary sexual characters |
| Ovaries | Oestrogen | Develops female secondary sexual characters |
Q5. What is HIV/AIDS? How does it spread and how can it be prevented?
Answer: AIDS (Acquired Immuno Deficiency Syndrome) is a deadly disease caused by a virus called HIV (Human Immunodeficiency Virus). The virus attacks the body’s immune system and weakens its ability to fight infections.
Modes of spread:
- Through transfusion of contaminated blood.
- Through use of infected needles or syringes.
- From an infected mother to her child during pregnancy or childbirth.
- Through unsafe physical contact with an infected person.
Prevention:
- Always use sterilised needles and syringes.
- Ensure that blood used for transfusion is properly tested.
- Avoid drug abuse and stay away from addictive substances.
- Spread awareness about HIV/AIDS in the community.
Additional Multiple Choice Questions (MCQs)
Q1. Adolescence in human beings begins at the age of about:
- (a) 5 years
- (b) 8 years
- (c) 11 years
- (d) 20 years
Answer: (c) 11 years
Q2. The master endocrine gland in the body is:
- (a) Thyroid
- (b) Pituitary
- (c) Pancreas
- (d) Adrenal
Answer: (b) Pituitary
Q3. The male sex hormone is:
- (a) Oestrogen
- (b) Insulin
- (c) Testosterone
- (d) Adrenaline
Answer: (c) Testosterone
Q4. The hormone that controls the level of sugar in the blood is:
- (a) Thyroxine
- (b) Adrenaline
- (c) Insulin
- (d) Oestrogen
Answer: (c) Insulin
Q5. The sex chromosomes in a human male are:
- (a) XX
- (b) XY
- (c) YY
- (d) XO
Answer: (b) XY
Q6. The first menstrual flow in girls is called:
- (a) Menopause
- (b) Ovulation
- (c) Menarche
- (d) Fertilisation
Answer: (c) Menarche
Q7. AIDS is caused by:
- (a) Bacteria
- (b) Fungus
- (c) HIV virus
- (d) Protozoa
Answer: (c) HIV virus
Q8. The hormone secreted by the thyroid gland is:
- (a) Insulin
- (b) Thyroxine
- (c) Adrenaline
- (d) Testosterone
Answer: (b) Thyroxine
Q9. The average duration of the menstrual cycle is:
- (a) 14 days
- (b) 21 days
- (c) 28 days
- (d) 35 days
Answer: (c) 28 days
Q10. Which of the following is called the “fight or flight” hormone?
- (a) Insulin
- (b) Thyroxine
- (c) Adrenaline
- (d) Oestrogen
Answer: (c) Adrenaline
Fill in the Blanks
- Q1. The period of life when reproductive maturity is attained is called __________. Answer: puberty
- Q2. The female sex hormone is __________. Answer: oestrogen
- Q3. The pituitary gland is also called the __________ gland. Answer: master
- Q4. The permanent stoppage of menstruation is called __________. Answer: menopause
- Q5. AIDS is caused by the __________ virus. Answer: HIV
True or False
- Q1. Adolescence ends when an individual is capable of reproduction. Answer: True
- Q2. The sex of a child is determined by the mother’s egg. Answer: False (it is determined by the father’s sperm)
- Q3. Insulin is secreted by the pancreas. Answer: True
- Q4. Junk food is the best diet during adolescence. Answer: False (a balanced diet is best)
- Q5. HIV can spread through the use of unsterilised needles. Answer: True
Glossary
| Term | Meaning |
|---|---|
| Adolescence | Period of life (11–19 years) during which the body matures for reproduction |
| Puberty | The age at which sexual maturity is attained |
| Hormones | Chemical substances secreted by endocrine glands that control body functions |
| Endocrine Gland | A ductless gland that secretes hormones directly into the blood |
| Pituitary Gland | The master gland in the brain that controls other endocrine glands |
| Testosterone | Male sex hormone secreted by testes |
| Oestrogen | Female sex hormone secreted by ovaries |
| Secondary Sexual Characters | External features that differentiate males from females after puberty |
| Menstruation | Monthly shedding of the uterine lining along with blood in females |
| Menarche | The first menstrual flow at puberty |
| Menopause | The permanent stoppage of menstruation around 45–50 years of age |
| Reproductive Phase | The years during which a woman is capable of bearing children |
| Sex Chromosomes | Chromosomes (X and Y) that determine the sex of an individual |
| Thyroxine | Hormone from the thyroid gland that regulates metabolism |
| Insulin | Hormone from the pancreas that controls blood sugar |
| Adrenaline | Hormone from adrenal glands that helps cope with stress |
| Growth Hormone | Hormone from pituitary that controls body growth |
| Reproductive Health | The total well-being of the reproductive system |
| HIV | Human Immunodeficiency Virus, the cause of AIDS |
| AIDS | Acquired Immuno Deficiency Syndrome, a disease that weakens the immune system |