CBSE Class 8 Science Chapter 7 Important Questions - Free PDF Download
FAQs on Important Questions for CBSE Class 8 Science Chapter 7 - Reaching The Age of Adolescence
1. What is the period of adolescence as per the CBSE Class 8 syllabus?
Adolescence is the transitional phase of growth and development between childhood and adulthood. According to the NCERT guidelines, this period generally corresponds to the teenage years, from about 11 to 19 years of age. It is a crucial time marked by rapid physical, psychological, and social changes.
2. From an examination perspective, what are the definitions of Puberty and Menarche?
For your Class 8 exams, it is important to know these definitions:
- Puberty: This is the period during adolescence when the body undergoes several changes and reaches reproductive maturity. It is initiated by hormones.
- Menarche: This term refers to the first menstrual flow or period that occurs in a female at the onset of puberty, typically between the ages of 10 and 12.
3. What are secondary sexual characteristics? List two important examples each for boys and girls.
Secondary sexual characteristics are the physical features that develop during puberty, which are not directly involved in reproduction but help distinguish between males and females. These are often asked as 3-mark questions.
- In Boys: Growth of facial hair (moustache and beard), deepening of the voice due to the growth of the voice box (Adam's apple).
- In Girls: Development of breasts, and broadening of the waist and hip region.
4. How is sex determined in a human child? Explain with reference to chromosomes.
This is a very important 5-mark question for the 2025-26 exams. The sex of a child is determined by the type of sex chromosome contributed by the male parent (father).
- Human cells have 23 pairs of chromosomes. The 23rd pair are the sex chromosomes.
- Females have two X chromosomes (XX). All their eggs carry only an X chromosome.
- Males have one X and one Y chromosome (XY). Their sperm can carry either an X or a Y chromosome.
- If a sperm with an X chromosome fertilises the egg (X), the child will be a girl (XX).
- If a sperm with a Y chromosome fertilises the egg (X), the child will be a boy (XY).
5. Why is it a misconception to blame the mother for the gender of a baby?
This is a high-order thinking skill (HOTS) question. Scientifically, the mother has no role in determining the gender of the child. A mother has an XX chromosome pair and can only contribute an X chromosome to the offspring. The father has an XY chromosome pair and produces two types of sperm: one carrying the X chromosome and the other carrying the Y. Therefore, it is the father's sperm that fertilises the egg which determines whether the baby will be a boy (XY) or a girl (XX).
6. Explain the function of the following endocrine glands for your exam: Pituitary gland and Pancreas.
Understanding the functions of endocrine glands is key for scoring well.
- Pituitary Gland: Often called the 'master gland', it secretes hormones that control other endocrine glands. It secretes growth hormone, which is essential for normal body growth, and also hormones that stimulate the testes and ovaries to produce their respective hormones.
- Pancreas: This gland secretes insulin, a hormone crucial for regulating blood sugar levels. A deficiency of insulin leads to diabetes.
7. Why is a balanced diet considered essential for adolescents?
Adolescence is a stage of rapid growth and development, making a balanced diet extremely important. A balanced diet provides:
- Energy for daily activities and growth, from carbohydrates and fats.
- Building blocks for muscle and tissue development, from proteins.
- Essential nutrients like vitamins and minerals (e.g., iron for blood formation and calcium for bone development) that support the body's many metabolic processes.
8. What is Adam's apple, and why is it more prominent in boys than in girls?
The Adam's apple is the protruding part of the throat cartilage that surrounds the larynx, or voice box. During puberty, the larynx grows significantly in both boys and girls. However, this growth is much more pronounced in boys, causing their voice to deepen and the cartilage to stick out. This makes the Adam's apple a prominent secondary sexual characteristic in males.
9. How does the endocrine system control the onset of puberty?
The onset of puberty is a hormonally controlled process orchestrated by the endocrine system. The sequence is as follows:
1. The pituitary gland secretes gonadotropins (hormones that act on the gonads).
2. These hormones stimulate the testes in males to produce testosterone and the ovaries in females to produce estrogen.
3. Testosterone and estrogen are then released into the bloodstream and travel to different parts of the body, triggering the development of secondary sexual characteristics and marking the beginning of reproductive maturity.
10. Explain the menstrual cycle. Why does menstruation occur?
The menstrual cycle is the reproductive cycle in females that begins at puberty. Each month, an ovary releases a mature egg (ovulation). In preparation, the wall of the uterus thickens to receive a fertilised egg. Menstruation occurs when fertilisation does not happen. In this case, the released egg and the thickened, blood-vessel-rich lining of the uterus are shed, resulting in bleeding. This cycle typically repeats every 28 to 30 days.
11. Why should adolescents be cautious about personal hygiene?
During adolescence, the activity of sweat and sebaceous (oil) glands increases significantly. This can lead to increased body odour and a higher chance of developing acne and pimples. Maintaining good personal hygiene, such as daily bathing and washing the face regularly, is crucial to prevent skin infections and stay clean and healthy.
12. What are the potential health risks of consuming drugs and alcohol during adolescence?
This is a crucial value-based question. Consuming drugs and alcohol during adolescence is extremely harmful because the body and brain are still developing. These substances are addictive and can lead to:
- Impaired brain development affecting memory and decision-making.
- Serious health problems like liver damage and heart disease.
- Mental health issues such as depression and anxiety.
- Risk of contracting diseases like AIDS through shared needles.
