CBSE Class 8 Science Reaching The Age of Adolescence Worksheets with Answers - Chapter 10 - PDF
FAQs on CBSE Class 8 Science Reaching The Age of Adolescence Worksheets
1. What types of questions, from 1-mark to 5-marks, can be expected in the CBSE Class 8 Science exam 2025-26 from the chapter 'Reaching the Age of Adolescence'?
For the 2025-26 board exams, you should prepare for a variety of question formats from this chapter. Key areas include:
- 1-mark questions: Focus on definitions like puberty, menarche, or naming a specific hormone like estrogen or testosterone.
- 2-mark questions: These often ask for lists, such as naming two changes during puberty in boys or listing two endocrine glands.
- 3-mark questions: Expect questions that require short explanations, like differentiating between primary and secondary sexual characters or explaining the function of the pituitary gland.
- 5-mark questions: These are for detailed explanations of biological processes, such as describing the human menstrual cycle or explaining the role of multiple hormones in the body.
2. What are secondary sexual characters? List two examples each for boys and girls that appear during puberty.
Secondary sexual characters are physical features that appear during puberty which distinguish males from females but are not directly involved in reproduction.
- In boys: Common examples include the growth of facial hair (moustache and beard) and the deepening of the voice.
- In girls: Key examples are the development of breasts and the widening of the pelvic region.
3. Explain the role of hormones in initiating reproductive functions in humans.
Hormones are chemical messengers that trigger the onset of puberty. The process is controlled by the endocrine system:
- The pituitary gland, often called the master gland, releases hormones that travel through the bloodstream to the gonads (sex organs).
- These hormones stimulate the testes in males to produce testosterone.
- They also stimulate the ovaries in females to produce estrogen.
- Testosterone and estrogen are responsible for the development of secondary sexual characters and the maturation of the reproductive system.
4. How is the sex of a baby determined in humans? Explain why it is incorrect to blame the mother for the sex of her child.
The sex of a baby is a matter of genetic chance determined by the sex chromosomes at the time of fertilisation.
- A human female has two X chromosomes (XX), so her egg cell will always contain one X chromosome.
- A human male has one X and one Y chromosome (XY), so his sperm can contain either an X or a Y chromosome.
- If a sperm with an X chromosome fertilises the egg, the resulting zygote is XX, and the baby will be a girl.
- If a sperm with a Y chromosome fertilises the egg, the zygote is XY, and the baby will be a boy.
Since the mother can only contribute an X chromosome, the sex of the child is determined solely by which type of sperm from the father fertilises the egg. Therefore, it is scientifically baseless and wrong to hold the mother responsible.
5. What is the menstrual cycle? Define the terms menarche and menopause in this context.
The menstrual cycle is the reproductive cycle that occurs in females after puberty. In this cycle, the wall of the uterus thickens to prepare for a fertilised egg. If fertilisation does not happen, this thickened uterine lining, along with its blood vessels, is shed. This results in bleeding, known as menstruation, which typically occurs once every 28 to 30 days.
- Menarche: This is the term for the very first menstrual flow, which marks the beginning of puberty and reproductive life in a girl.
- Menopause: This is the term for the permanent cessation of the menstrual cycle, which usually happens between the ages of 45 and 50, marking the end of a woman's reproductive phase.
6. Why is it important for an adolescent to maintain personal hygiene and consume a balanced diet?
During adolescence, the body undergoes rapid growth and significant hormonal changes, making nutrition and hygiene critically important.
- Balanced Diet: The body is in a major growth spurt, requiring increased energy and nutrients. A balanced diet rich in proteins, carbohydrates, fats, vitamins, and minerals is essential for proper bone and muscle development. Iron is particularly important for girls to compensate for blood loss during menstruation and prevent anaemia.
- Personal Hygiene: The activity of sweat glands and sebaceous (oil) glands increases significantly during adolescence. This can lead to body odour and acne. Regular bathing and keeping the body clean are crucial to prevent skin infections and maintain overall health.
7. What are endocrine glands, and why are they also known as 'ductless glands'?
Endocrine glands are specialized organs that produce chemical substances called hormones. They are called 'ductless glands' because they release their hormones directly into the bloodstream, which then transports them to various target organs throughout the body. They do not have tubes or ducts to carry their secretions, unlike glands such as salivary or sweat glands.
8. Besides the sex hormones, what is the role of the thyroid and adrenal glands during adolescence?
While sex hormones drive reproductive changes, other endocrine glands are also very active during adolescence.
- Thyroid Gland: This gland secretes thyroxine, a hormone crucial for regulating the body's overall metabolism, energy production, and supporting balanced growth of the body, bones, and hair. A properly functioning thyroid is essential for the adolescent growth spurt.
- Adrenal Gland: This gland secretes adrenaline, which helps the body manage stress and respond to 'fight or flight' situations. This is important as adolescents often face new social and academic pressures.
