Class 8 Science Chapter 7 Question Answers - Reaching the Age of Adolescence

Q1: Why do boys have a hoarse voice at puberty?
Ans: The voice box or larynx begins to grow at the onset of puberty. This growing voice box in boys can be seen as a protruding part of the throat called Adam’s apple. This leads to the voice becoming hoarse.

Q2: What is meant by adolescence?
Ans: Growing up is a natural process. The period of life, when the body undergoes several changes leading to reproductive maturity, is called adolescence. The adolescence period is 11 to 19 years of age.

Q3: What are secondary sexual characters?
Ans: At puberty, in girls, breasts begin to develop, the region below the waist becomes wider, voice becomes shriller. Boys begin to grow facial hair, i.e., moustache and beard. Boys also develop hair on their chest, the muscles of the body grow more prominently, develop a larger voice box which can be seen as a protruding part of the throat called Adam’s apple. In both boys and girls, hair grows under the arms and in the pubic region. As these features distinguish the male from the female they are called secondary sexual characters.

Q4: What is the role of hormones in completing the life history of insects and frogs?
Ans: Hormones play an important role in the completion of the life cycle of insects and frogs. Metamorphosis in insects is controlled by insect hormones. In a frog, it is controlled by thyroxine, the hormone produced by the thyroid gland. Thyroxine production requires the presence of iodine in the water. Water in which iodine is not present, the tadpoles cannot become adults.

Q5: What is menstruation?
Ans: At puberty, in girls, the ovaries get enlarged and start producing eggs (ovum). One egg matures and is released by one of the ovaries once in about 28 to 30 days. During this period, the wall of the uterus becomes thick so as to receive the egg. If the egg is fertilized, then it begins to develop and results in pregnancy. If this egg is not fertilized, the released egg and thickened lining of the uterus along with its blood vessels are shed off causing bleeding in females which is called menstruation. It occurs once in about 28 to 30 days.

Q6: What are the changes in males at puberty?
Ans: There are various changes in males at puberty. They are:

• sudden increase in height.
• growth of hair at different parts of the body like face, armpit, and pubic region, development of moustache and beard.
• development of Adam’s apple in the throat, voice becomes hoarse.
• shoulders become broader and chest wider.
• growth in the size of reproductive organs like penis, testes begin to produce sperms, etc.

Q7: What is the function of the hormone released by the pancreas?
Ans: Insulin is released by the pancreatic gland. It regulates sugar metabolism. If insulin is deficient in the body, the sugar level becomes high in the blood causing diabetes.

Q8: What are sex hormones? How do they work in the human body?
Ans: Sex hormones help boys and girls develop sex organs to enable them for reproduction. These hormones lead them to reproductive maturity.
In girls, estrogen makes the breasts develop. Milk-secreting glands or mammary glands develop inside the breasts. Ovaries begin to produce eggs. In boys, testosterone is released by testes. Testes begin to release sperms. Changes in boys are also seen due to this hormone.

Q9: What are the changes in females at the onset of puberty?
Ans: There are several changes in females at the onset of puberty. They are:

• growth of hair in the armpit and pubic region.
• development of breasts and mammary glands.
• ovaries get enlarged and begin producing eggs.
• menstruation cycle starts; and
• increased activity of sweat and sebaceous glands.

Q10: What is puberty?
Ans: The period during which adolescent boys and girls attain sexual maturity and become capable of reproduction is called puberty. Puberty age for females is 10 to 12 years while male puberty age is 12 to 14 years.

Q11: What is a pituitary gland?
Ans: Different types of hormones are secreted by different types of glands. The production of all these hormones is under the control of another hormone secreted from an endocrine gland called the pituitary gland.

Q12: What is vital change that marks puberty in boys and girls?
Ans: During puberty, the human body undergoes several changes, but the most important change that marks puberty is that boys and girls become capable of reproduction.

Q13: What is reproductive health?
Ans: Reproductive health refers to the diseases, disorders, and conditions that affect the functioning of the male and female reproductive system during all stages of life.

Q14: What happens when the egg is fertilized?
Ans: When the egg is fertilized, it begins to divide and then gets embedded in the uterus for further development. Finally, the fertilized egg develops into a fetus.

Q15: How does the body shape change at puberty?
Ans: Body shape changes differently in boys and girls at puberty. Boys have broader shoulders and wider chests. Their muscles grow more prominently than girls. In girls, the region below the waist becomes wider.

Q16: Why are endocrine glands also called ductless glands?
Ans: Endocrine glands release hormones directly into the bloodstream. So, they are termed as ductless glands. For example, pituitary, thyroid, pancreas, etc.

Q17: What is a pancreas?
Ans: The pancreas is an endocrine gland that releases hormones such as insulin to regulate sugar metabolism and maintain blood sugar levels in the body.

Q18: How do hormones work in the human body?
Ans: Endocrine glands release hormones into the bloodstream to reach a particular body part called the target site. The target responds to the hormone. There are many endocrine glands or ductless glands in the body.

Q19: What are the changes in males and females at puberty?
Ans: At puberty, both males and females undergo a series of physical changes. In females, the development of breasts, growth of pubic and underarm hair, widening of hips, and the onset of menstruation occur. In males, the growth of facial hair, deepening of voice, growth of pubic and body hair, and enlargement of the testes and penis occur.

Q20: What are the roles of sex hormones in the human body?
Ans: Sex hormones, such as estrogen in females and testosterone in males, play a crucial role in the development of secondary sexual characteristics, including the growth of reproductive organs, the appearance of body hair, and changes in voice pitch. They also regulate the menstrual cycle in females and contribute to sexual maturity.

Q21: Explain the terms menarche and menopause.
Ans: Menarche is the term used to describe the first occurrence of menstruation in females, marking the onset of their reproductive capability. Menopause, on the other hand, refers to the natural cessation of menstruation and reproductive functions in females typically around the age of 45 to 50.

Q22: Which hormone is released by the pituitary gland? What is its function?
Ans: The pituitary gland releases a variety of hormones, including growth hormone, thyroid-stimulating hormone, follicle-stimulating hormone, and luteinizing hormone. These hormones play essential roles in regulating growth, metabolism, and the functions of other endocrine glands in the body.

Q23: Explain the term reproductive health. What should we do to maintain reproductive health?
Ans: The state of physical, mental and social well being of an individual is regarded as an individual’s health. A healthy person is free from disease, tension and anxiety. Reproductive health refers to a state of physical, mental and social well-being in all matters relating to the reproductive system, at all stages of life. We should take following measures to maintain reproductive health:

• To have a balanced diet: As far as practicable, we should have a balanced diet, i.e., a diet contain¬
• ing proteins, vitamins, carbohydrates, fats and minerals. We can have our food which contain these nutrients.
• To take physical exercise: We should take physical exercise like morning walk, running, etc., daily.
• To maintain personal hygiene: We should maintain personal hygiene to stay fit and healthy. We should wash our body especially pubic region, armpit, etc., properly.
• Avoid harmful drugs: We should avoid taking harmful drugs and alcohol.

Q24: Explain the reproductive phase of life in humans.
Ans:

• Boys and girls become capable of reproduction at puberty because their testes and ovaries begin to release gametes, i.e., sperms and ova respectively. In girls, reproductive phase of life begins at puberty from 10 to 12 years of age and generally lasts till the age of 45 to 50 years. The ova begin to mature with the onset of puberty. The ovum matures and is released by one of the ovaries once in 28 to 30 days.
• During this period, the wall of the uterus becomes thick so as to receive the egg, in case it is fertilised and begins to develop. This results in pregnancy.
• If fertilisation does not occur, the released egg, and the thickened lining of the uterus along with its blood vessels are shed off. This causes menstruation. It occurs once in about 28 to 30 days. The first menstrual flow begin at puberty and is termed as menarche. The menstruation stops at the age of 45 to 50. This stage is known as menopause.
• In male, the reproductive phase begins at puberty at the ages 14-15 and lasts as long as he is healthy.

Q25: What changes occur in human at puberty?
Ans: There are various changes in human at puberty. They are as follows:

• Change in height: During puberty, there is sudden increase in height in boys and girls. Initially, girls grow faster in height than in boys. But both reach their maximum height at the age of 18 years.
• Change in voice: Boys develop larger voice box or larynx to form protruding part of throat called Adam’s apple making their voice hoarse, girls have high pitched voice.
• Change in body shape: In boys, shoulders broaden and muscles grow more prominently than in girls. In girls the region below the waist becomes wider.
• Secretion of sweat and sebaceous glands (oil glands) in both boys and girls increases and acne or pimples grow on faces of many youths.
• Development of sex organs: In males, testes and penis develop completely. Testes begin producing sperms. In girls, ovaries are enlarged and begin to produce eggs. Both boys and girls reach reproductive maturity.
• In girls, menstruation or periods starts.
• All human beings attain mental, intellectual and emotional maturity at puberty.
• Facial hair like moustache and beard are grown in boys. Hair are grown in armpit and pubic region in both boys and girls. Breasts are developed in girls. These characters are called secondary sexual characters as they distinguish a male from a female.