07. Class 8 Science Chapter 7 Reaching The Age of Adolescence Notes Estimated reading: 10 minutes 33 views Welcome to Class 8 Science Chapter 7 Reaching The Age of Adolescence Notes. Introduction Adolescence is a transitional phase between childhood and adulthood. It is the stage when children become capable of reproduction. Adolescents are between the ages of 11 and 19 and are often referred to as teenagers. Adolescence Adolescence is a transitional phase between childhood and adulthood. It typically starts around the age of 11 and lasts until 18 or 19. Adolescents are often referred to as “teenagers” because this period covers the ‘teens.’ It’s characterized by various physical, emotional, and psychological changes. Changes at Puberty One of the most noticeable changes during puberty is the rapid increase in height. This growth spurt is due to the elongation of long bones in the arms and legs. Growth during adolescence is not uniform, and different individuals may grow at different rates. It’s common for adolescents to experience disproportionate growth, where certain body parts, like arms or legs, may appear oversized at first. However, this usually evens out over time. Change in Body Shape During puberty, boys typically develop broader shoulders and wider chests, while girls’ hips become wider. Muscles grow more prominently in boys, leading to a more muscular appearance. The changes occurring in adolescent boys and girls are different and contribute to their gender-specific physical characteristics. This diversity in physical development is perfectly normal. Voice Change Boys’ voices often undergo significant changes during puberty. The voice box, or larynx, begins to grow and expand, making boys’ voices deeper. Some adolescent boys may experience voice cracking, a temporary phase due to the changing voice box. Girls’ voices may also experience changes but not as pronounced as in boys. Increased Activity of Sweat and Sebaceous Glands Puberty triggers an increase in the activity of sweat and sebaceous (oil) glands. This can lead to issues like acne, as the increased gland activity may result in clogged pores and pimples. Boys often start growing facial hair, including mustaches and beards, during this time. Girls and boys both experience the growth of body hair, including underarm hair and pubic hair. Development of Sex Organs During puberty, male sex organs, such as the testes and penis, develop fully. The testes also start producing sperm during this time. In girls, the ovaries enlarge and eggs begin to mature. Ovaries also start releasing mature eggs. These developments are crucial for the reproductive capability of boys and girls. Role of Hormones in Initiating Reproductive Function Hormones play a vital role in triggering the changes associated with puberty. The onset of puberty is controlled by hormones from the pituitary gland, an endocrine gland located in the brain. The male hormone, testosterone, and the female hormone, estrogen, are responsible for many of the changes that occur in boys and girls during adolescence. Reproductive Phase of Life in Humans Adolescents become capable of reproduction once their reproductive organs, like the testes and ovaries, begin producing gametes (sperm and eggs). The reproductive phase in females begins at puberty and typically lasts until the age of 45 to 50. The menstrual cycle in females involves the maturation and release of eggs, thickening of the uterine wall, and its breakdown if pregnancy does not occur. The onset of menstruation is called menarche, and the cessation of the menstrual cycle is known as menopause. How is the Sex of the Baby Determined? The sex of an unborn baby is determined by the combination of sex chromosomes contributed by the parents. Females have two X chromosomes (XX), and males have one X and one Y chromosome (XY). If a sperm carrying an X chromosome fertilizes the egg, it results in a female (XX), and if a sperm with a Y chromosome fertilizes the egg, it leads to a male (XY). Hormones other than Sex Hormones In addition to sex hormones, various other hormones play essential roles in the body. Hormones like thyroxine, insulin, and adrenalin are secreted by different endocrine glands and have specific functions. For instance, thyroxine is produced by the thyroid gland and regulates metabolism, while insulin is produced by the pancreas and helps regulate blood sugar levels. Conclusion Keywords and Definitions Important Definitions for Class 8 Science Chapter 7 Reaching The Age of Adolescence Notes. 1. Adolescence Definition: Adolescence is the transitional phase between childhood and adulthood, typically occurring between the ages of 11 and 18 or 19. It is characterized by significant physical, emotional, and psychological changes. 2. Puberty Definition: Puberty is the biological process during adolescence when an individual’s body undergoes various physical changes, leading to sexual maturity and the ability to reproduce. 3. Larynx Definition: The larynx, commonly known as the voice box, is an organ in the throat that houses the vocal cords and plays a crucial role in sound production and speech. 4. Sebaceous Gland Definition: Sebaceous glands are microscopic glands in the skin that produce sebum, an oily substance that helps keep the skin and hair moisturized. Overactivity of these glands can lead to skin issues like acne. 5. Acne Definition: Acne is a common skin condition characterized by the development of pimples, blackheads, whiteheads, and other skin blemishes. It is often associated with increased activity of sebaceous glands during puberty. 6. Testicle Definition: A testicle, also known as a testis, is the male reproductive organ responsible for producing sperm and testosterone, a key male sex hormone. 7. Ovary Definition: The ovary is the female reproductive organ responsible for producing eggs and female sex hormones, including estrogen and progesterone. 8. Pituitary Gland Definition: The pituitary gland is a small endocrine gland located at the base of the brain. It plays a vital role in regulating various bodily functions by releasing hormones. 9. Testosterone Definition: Testosterone is the primary male sex hormone responsible for the development of male sexual characteristics, such as a deep voice, facial hair, and muscle growth. 10. Estrogen Definition: Estrogen is the primary female sex hormone responsible for the development of female sexual characteristics and regulating the menstrual cycle. 11. Menstrual Cycle Definition: The menstrual cycle is a regular, monthly series of changes in the female reproductive system, including the maturation and release of eggs and the thickening of the uterine lining. 12. Menarche Definition: Menarche is the first occurrence of menstruation in females, marking the onset of the reproductive phase of life. 13. Menopause Definition: Menopause is the natural biological process that marks the end of a woman’s reproductive years, characterized by the cessation of the menstrual cycle. 14. Sex Chromosome Definition: Sex chromosomes are a pair of chromosomes that determine an individual’s biological sex. Females typically have two X chromosomes (XX), and males have one X and one Y chromosome (XY). 15. Thyroxine Definition: Thyroxine is a hormone produced by the thyroid gland that regulates the body’s metabolism and energy expenditure. 16. Insulin Definition: Insulin is a hormone produced by the pancreas that plays a critical role in regulating blood sugar levels by facilitating the uptake of glucose by cells. 17. Adrenaline Definition: Adrenaline, also known as epinephrine, is a hormone and neurotransmitter produced by the adrenal glands that helps the body respond to stress and emergency situations by increasing heart rate and energy levels. Recap and Questions Important Questions and Answers for Class 8 Science Chapter 7 Reaching The Age of Adolescence Notes. Frequently Asked Questions (FAQs) with Answers FAQ for Class 8 Science Chapter 7 Reaching The Age of Adolescence Notes. 1. Q: What is puberty? A: Puberty is a natural process of physical and emotional changes that occur as adolescents transition from childhood to adulthood. 2. Q: When does puberty typically begin? A: Puberty usually begins around the age of 11 to 12 for girls and 12 to 13 for boys, although it can vary. 3. Q: What are the primary physical changes during puberty? A: Physical changes include growth spurts, the development of secondary sexual characteristics (like breast development in girls and facial hair in boys), and changes in voice pitch. 4. Q: What hormonal changes drive puberty? A: Puberty is triggered by changes in hormone levels, with increased production of estrogen in girls and testosterone in boys. 5. Q: What is the significance of the menstrual cycle in girls during puberty? A: The menstrual cycle is a key aspect of female puberty, marking the ability to conceive, but it also involves hormonal fluctuations and uterine changes. 6. Q: Why do adolescents often experience acne during puberty? A: Acne is common during puberty due to increased sebum (skin oil) production, which can clog pores and lead to breakouts. 7. Q: How do hormones affect emotional changes during puberty? A: Hormones play a role in mood swings and emotional changes during puberty, but they are not the sole factor; social and environmental factors also contribute. 8. Q: What are the psychological changes that adolescents undergo during puberty? A: Adolescents may experience greater independence, self-identity exploration, and shifts in relationships with peers and parents. 9. Q: Are there any health concerns related to puberty? A: Health concerns can include eating disorders, substance use, and mental health issues, making it crucial to provide support and guidance. 10. Q: How can parents and educators support adolescents during puberty? A: Open communication, understanding, and providing a safe space for questions and concerns are essential for supporting adolescents through this transformative period. Multiple Choice Questions (MCQs) MCQ for Class 8 Science Chapter 7 Reaching The Age of Adolescence Notes. 1. Q: What is the primary female sex hormone responsible for the development of secondary sexual characteristics during puberty? A: Estrogen B: Progesterone C: Testosterone D: Insulin Answer: A: Estrogen 2. Q: In boys, which hormone is primarily responsible for the deepening of the voice during puberty? A: Estrogen B: Progesterone C: Testosterone D: Growth hormone Answer: C: Testosterone 3. Q: Which of the following is a common physical change that both boys and girls experience during puberty? A: Menstruation B: Facial hair growth C: Voice deepening D: Breast development Answer: D: Breast development 4. Q: What role do sebaceous glands play in adolescent acne during puberty? A: Sebaceous glands produce sweat B: Sebaceous glands produce hair C: Sebaceous glands produce oil D: Sebaceous glands produce blood Answer: C: Sebaceous glands produce oil 5. Q: During puberty, emotional changes in adolescents are primarily due to which factor? A: Hormones B: Genetics C: Diet D: Exercise Answer: A: Hormones 6. Q: What is the term for the psychological process during which adolescents explore and establish their self-identity? A: Regression B: Identity crisis C: Conformity D: Obedience Answer: B: Identity crisis 7. Q: What is a common eating disorder that may emerge during puberty, characterized by food restriction and fear of gaining weight? A: Diabetes B: Anorexia nervosa C: Obesity D: Bulimia Answer: B: Anorexia nervosa 8. Q: Substance use during adolescence can lead to various health issues. Which of the following is NOT a potential consequence of substance abuse? A: Addiction B: Improved academic performance C: Legal problems D: Health problems Answer: B: Improved academic performance 9. Q: What should parents and educators prioritize to support adolescents during puberty? A: Strict discipline B: Open communication C: Isolation D: Perfectionism Answer: B: Open communication 10. Q: What is the average age range for the onset of puberty in girls? – A: 5-6 years B: 8-9 years C: 11-12 years D: 14-15 years Answer: C: 11-12 years This was the end of Class 8 Science Chapter 7 Reaching The Age of Adolescence Notes. For further information, refer to NCERT SOLUTIONS, NCERT NOTES, and NCERT BOOKS .
