Class 8 Science Chapter 7 Reaching the Age of Adolescence Solutions

Question 1: What is adolescence? When does it begin?

Answer: The period of life when the body undergoes changes leading to reproductive maturity is called adolescence. It begins around the age of 11 and lasts up to 18 or 19 years of age.

Question 2: What is the most important change that marks puberty?

Answer: The most important change that marks puberty is that boys and girls become capable of reproduction. Puberty ends when an adolescent reaches the reproductive majority.

Question 3: What are the various factors that affect the height of a person?

Answer: The factors affecting the height of a person are:

(i) It depends on the genes inherited from the parents. Therefore, the height of an individual is more or less similar to that of family members.

(ii) It depends on the diet taken by the person during the growing years.

Question 4: What changes in body shapes do boys and girls undergo during adolescence?

Answer: In boys, the shoulders become broad, the chest becomes wider and the muscles of the body grow more prominently. In girls, the region below the waist becomes wider and the breast begins to develop.

Question 5: What are the changes that occur in the voice of boys and girls during puberty?

Answer: At puberty, the voice box or larynx begins to grow. Boys develop larger voice boxes which can be seen as a protruding part of the throat called Adam’s apple. In girls, the larynx is of small size and is hardly visible from the outside. Generally, girls have a high-pitched voice whereas boys have a deep voice.

Question 6: Why do young people get acne or pimples on the face at the time of puberty?

Answer: Young people get acne or pimples on the face at the time of puberty as the secretion of sweat glands and sebaceous glands (oil glands) increases during puberty.

Question 7: How do sex organs develop during puberty?

Answer: At puberty, male sex organs like the testes and penis develop completely. The testes also begin to produce sperm. In girls, the ovaries enlarge and eggs begin to mature. Also, ovaries start releasing mature eggs called ovum.

Question 8: How does adolescence affect the thinking pattern of an individual?

Answer: During adolescence intellectual development takes place and youngsters tend to spend considerable time thinking. It is often the time when the brain has the greatest capacity for learning.

Question 9: What are secondary sexual characters? How do they vary from male to female?

Answer: The features that help us to distinguish a male from a female are known as secondary sexual characters.

In girls, breasts develop and the region below the waist becomes wider. Boys begin to grow facial hair which is a mustache and beard. Boys also develop hair on their chests. In both boys and girls hair grows under the arms and in regions above the thigh or the pubic region.

Question 10: What are hormones?

Answer: Hormones are chemical substances secreted by endocrine glands. The changes that occur in adolescence are controlled by hormones.

Question 11: How do hormones work?

Answer: Endocrine glands release hormones into the bloodstream to reach a particular body part called the target site and the target site responds to the hormone.

Question 12: What is the legal age of marriage for boys and girls in India?

Answer: In India, the legal age for marriage is 18 years for girls and 21 years for boys.

Question 13: What is menarche and menopause?

Answer: The first menstrual flow of a woman begins at puberty and is called menarche. The stoppage of the menstrual cycle in women at around 45 to 50 years of age is called menopause.

Question 14: What is goitre?

Answer: Goitre is a disease in which the production of thyroxine from the thyroid gland stops and the gland enlarges.

Question 15: How is diabetes caused?

Answer: Diabetes is a disease caused by insufficient production of insulin by the pancreas.

Question 16: Why is the pituitary gland known as the master gland?

Answer: The pituitary gland is attached to the brain and it secretes hormones that regulate the secretion of hormones by other endocrine glands. The hormones secreted by the pituitary gland stimulate the testes and ovaries to produce their hormones. Adrenal and thyroid secrete their hormones when they receive orders from the pituitary gland. It also secretes growth hormones necessary for the normal growth of a person.

Question 17: Describe the functions of the adrenal gland.

Answer: The adrenal gland secretes a hormone called adrenalin which helps to manage stress in the body. It also maintains the correct balance of the salt in the body.

Question 18: What is menstruation? Explain.

Answer: With the onset of puberty, the ovum matures and is released by the ovaries once in about 28 to 30 days and the walls of the uterus become thick to receive egg. If the egg is fertilized it results in puberty. If fertilization does not occur the released egg and the thickened lining of the uterus along with its blood vessels are shed off causing bleeding in women and is known as menstruation.

Question 19: Why drugs should be taken only on a prescription from a doctor?

Answer: Drugs are addictive. If you take them once you will feel like taking them again and again. They harm the body in the long run and ruin health and happiness.

Question 20: What is the role of hormones in completing the life of frogs?

Answer: Metamorphosis includes various stages a tadpole passes through from larva to adult frog. In a frog, metamorphosis is controlled by thyroxine produced by the thyroid. Thyroxine production requires the presence of iodine in water. If the water in which tadpoles are growing does not contain sufficient iodine, the tadpoles cannot become adults.

Question 21: How can you keep your body healthy during adolescence?

Answer: (i) Eat a balanced and nutritious diet.

(ii) Take special care of your hygiene.

(iii) Walk and play in fresh air.

(iv) Add exercise to your daily routine and play outdoor games.

(v) Stay away from drugs and alcohol.

Question 22: How is AIDS caused and how is it transmitted?

Answer: AIDS is caused by a dangerous virus called HIV. It is transmitted from an infected person to a healthy person in the following ways:

(i) By using infected syringes.

(ii) By an infected mother to an infant from her milk.

(iii) By sexual contact with a person infected with HIV.