CLASS 8 SCIENCE CHAPTER 10 REACHING THE AGE OF ADOLESCENCE
NCERT Class 8 Science – Chapter 10: Reaching the Age of Adolescence
Important Questions and Answers
A. Very Short Answer Questions
Q1. What is adolescence?
Answer: Adolescence is the period of life when a child undergoes physical, mental and emotional changes and gradually develops towards adulthood. It generally begins around 11 years of age and may continue up to 18 or 19 years.
Q2. What is puberty?
Answer: Puberty is the stage during adolescence when the body becomes capable of reproduction due to hormonal changes.
Q3. What are hormones?
Answer: Hormones are chemical substances produced by endocrine glands that regulate various activities of the body.
Q4. What is the endocrine system?
Answer: The endocrine system is a group of glands that release hormones into the bloodstream to control and coordinate body functions.
Q5. Name the male sex hormone.
Answer: Testosterone is the main male sex hormone.
Q6. Name the main female sex hormones.
Answer: Oestrogen is a major female sex hormone. Progesterone is another important female reproductive hormone.
Q7. What is menstruation?
Answer: Menstruation is the periodic shedding of the uterine lining, accompanied by bleeding, when pregnancy does not occur.
Q8. What is the Adam's apple?
Answer: The Adam's apple is the prominent part of the voice box that often becomes more noticeable in boys during puberty.
Q9. What are secondary sexual characteristics?
Answer: Secondary sexual characteristics are physical features that develop during puberty and help distinguish adult males and females, apart from their reproductive organs.
Q10. What is the normal duration of the menstrual cycle?
Answer: A typical menstrual cycle lasts about 28 days, although the length can vary considerably, especially during the first few years after menstruation begins.
B. Short Answer Questions
Q11. What changes occur during adolescence?
Answer: The major changes during adolescence include:
Increase in height.
Changes in body shape.
Growth of hair in the armpits and pubic region.
Changes in the voice.
Maturation of reproductive organs.
Increased activity of sweat and oil glands.
Emotional and mental development.
Q12. What is the role of hormones during puberty?
Answer: Hormones regulate the changes that occur during puberty. Testosterone helps bring about changes in boys, while oestrogen helps bring about changes in girls. Hormones also stimulate the maturation of reproductive organs.
Q13. Why do adolescents grow rapidly?
Answer: During adolescence, bones and muscles grow quickly under the influence of hormones. This causes a rapid increase in height. The timing and rate of growth vary from person to person.
Q14. Why does the voice change during puberty?
Answer: During puberty, the voice box, or larynx, grows. In boys, it generally grows more prominently, making the voice deeper. Girls may also experience changes in their voices, usually to a lesser extent.
Q15. What are endocrine glands? Give examples.
Answer: Endocrine glands are glands that release hormones directly into the bloodstream. Examples include:
Pituitary gland
Thyroid gland
Adrenal glands
Pancreas
Testes
Ovaries
Q16. What is the role of the pituitary gland?
Answer: The pituitary gland produces hormones that regulate growth and control the activities of several other endocrine glands. It also releases hormones involved in reproductive development.
Q17. Why is a balanced diet important during adolescence?
Answer: Adolescents need a balanced diet because their bodies are growing rapidly. A balanced diet provides proteins, carbohydrates, fats, vitamins, minerals and other nutrients needed for healthy growth, strong bones and normal body functions.
Q18. Why is personal hygiene important during adolescence?
Answer: Hormonal changes can increase sweating and oil production in the skin. Regular bathing, clean clothes, proper dental care and suitable menstrual hygiene help maintain cleanliness and reduce the risk of certain infections.
Q19. Why is iodine important for the body?
Answer: Iodine is needed by the thyroid gland to produce thyroid hormones. These hormones help regulate growth, development and metabolism. Iodised salt is a common source of iodine.
Q20. What is the function of insulin?
Answer: Insulin is a hormone produced by the pancreas. It helps regulate blood glucose levels by enabling body cells to take up glucose and by supporting its storage.
C. Long Answer Questions
Q21. Explain the major physical changes that occur during puberty.
Answer: Puberty brings several physical changes to the human body.
Increase in height: Bones lengthen rapidly, leading to a growth spurt.
Change in body shape: Boys generally develop broader shoulders, while girls generally develop wider hips.
Growth of body hair: Hair develops in the armpits and pubic region. Facial hair often develops in boys.
Voice changes: The voice box grows, and the voice usually becomes deeper in boys.
Maturation of reproductive organs: The testes and penis mature in boys, while the ovaries and uterus mature in girls.
Increased gland activity: Sweat and oil glands become more active, sometimes causing body odour and pimples.
The timing and extent of these changes differ among individuals. Such differences are a normal part of development.
Q22. Explain the role of hormones in human development.
Answer: Hormones are chemical messengers that regulate growth, development and reproduction.
Growth hormone: Produced by the pituitary gland; supports growth of the body.
Thyroxine: Produced by the thyroid gland; regulates metabolism and supports normal growth and development.
Insulin: Produced by the pancreas; helps control blood glucose levels.
Testosterone: Produced mainly by the testes; brings about many male pubertal changes and supports sperm production.
Oestrogen: Produced mainly by the ovaries; contributes to female pubertal changes and reproductive development.
Adrenaline: Produced by the adrenal glands; prepares the body to respond to stressful or emergency situations.
Hormones work in coordination to maintain normal body functions.
Q23. Describe the menstrual cycle.
Answer: The menstrual cycle is a series of changes that occur in the female reproductive system.
The lining of the uterus becomes thicker in preparation for a possible pregnancy.
An ovary usually releases an egg during ovulation.
If fertilisation occurs and the embryo implants successfully, pregnancy may begin.
If pregnancy does not occur, the thickened uterine lining breaks down and is shed as menstrual bleeding.
The cycle then begins again.
A cycle often lasts around 28 days, but natural variation is common.
Q24. How can adolescents maintain good health?
Answer: Adolescents can maintain good health by following these habits:
Eat a balanced diet containing fruits, vegetables, grains, protein-rich foods and adequate sources of calcium and iron.
Exercise regularly and participate in outdoor activities.
Get sufficient sleep.
Maintain personal and dental hygiene.
Drink safe water.
Avoid tobacco, alcohol and other harmful substances.
Talk to a trusted adult or healthcare professional when worried about physical or emotional changes.
Q25. Why is sex determination of a baby not controlled by the mother?
Answer: In humans, an egg normally carries an X chromosome, while a sperm carries either an X or a Y chromosome.
If an X-carrying sperm fertilises the egg, the usual chromosome pattern is XX.
If a Y-carrying sperm fertilises the egg, the usual chromosome pattern is XY.
Therefore, the sperm contributes the chromosome that determines the usual chromosomal sex pattern. The mother should not be blamed for the sex of a baby.
D. Fill in the Blanks
The period between childhood and adulthood is called adolescence.
The stage when reproductive maturity develops is called puberty.
Hormones are released by endocrine glands.
The main male sex hormone is testosterone.
A major female sex hormone is oestrogen.
The pituitary gland produces growth hormone.
The thyroid gland needs iodine to make thyroid hormones.
Insulin helps regulate blood glucose levels.
The voice box is also called the larynx.
The periodic shedding of the uterine lining is called menstruation.
E. True or False
Adolescence involves physical and emotional changes. — True
All adolescents begin puberty at exactly the same age. — False
Hormones act as chemical messengers. — True
The thyroid gland produces insulin. — False
Testosterone is the main male sex hormone. — True
Oestrogen plays an important role in female reproductive development. — True
A balanced diet is unnecessary during adolescence. — False
Iodine is needed for the production of thyroid hormones. — True
The menstrual cycle is exactly 28 days in every person. — False
Regular physical activity supports good health during adolescence. — True
F. Important Exam Questions for Revision
Define adolescence and puberty.
List the major changes that occur during puberty.
What are hormones? Explain their role in adolescence.
Name the major endocrine glands and their functions.
Explain the menstrual cycle.
What are secondary sexual characteristics?
Why is a balanced diet important during adolescence?
Explain the functions of the pituitary and thyroid glands.
Why is iodine important for the body?
Explain how the sex of a human baby is determined by chromosomes.
Crop Production And Management
Microorganisms - Friend And Foe
Synthetic Fibre And Plastic
Comments
Post a Comment