Lakhmir Singh & Manjit Kaur: Reaching The Age Adolescence- 1 | Lakhmir Singh & Manjit Kaur Solutions: Class 8 Science PDF Download

Q.1. What is the special name of the period of life between childhood and adulthood?

The period of life between childhood and adulthood is called adolescence.

Q.2. Name another term for ‘adolescents’.

Adolescents are also called teenagers.

Q.3. State the age at which adolescence usually begins and the age up to which it lasts.

Adolescence begins around the age of 11 and lasts upto 18 or 19 years of age.

Q.4. Which is the most conspicuous change (clear visible change) in boys and girls during puberty?

The most conspicuous change (clear visible change) in boys and girls during puberty is the sudden increase in height.

Q.5. How does the height of boys and girls change during puberty?

The long bones of arms and legs elongate and make a person tall.

Q.6. Name one factor on which the height of a person depends.

The height of a person depends on the genes inherited from parents.

Q.7. A nine year old boy is 120 cm tall. If the present height of boy is 75% of his full height, calculate the full height which the boy will eventually reach at the end of growth period.

Q.8. How do shoulders and chest change in boys during puberty?

As boys enter in puberty stage, their shoulders become broad and chest become wide.

Q.9. How do hips of girls change during puberty?

During puberty, the region below the waist becomes wider in girls.

Q.10. What is the other name of ‘voice box’?

Voice box is also known as larynx.

Q.11. Which of the two have a smaller voice box: grown up boys or grown up girls?

Grown up girls have a smaller voice box than grown up boys.

Q.12. What is the common name of the bulge (or projection) at the front of throat in grown up boys?

The common name of the bulge (or projection) at the front of throat in grown up boys is Adam’s apple.

Q.13. What substance is secreted by sebaceous glands?

Sebaceous glands secrete oil.

Q.14. Name the time period in one’s life when the brain has the greatest capacity for learning.

Adolescence is a period of time in in one’s life when the brain has the greatest capacity for learning.

Q.15. Name two glands present in the skin whose increased activity causes pimples and acne.

Sweat glands and sebaceous glands are present in the skin and causes pimples and acne.

Q.16. What name is given to those sexual characteristic in humans:
(a) which are present in babies at birth?
(b) which develop in mature boys and girls?

(a) Sexual characteristics which are present in babies at birth are called primary sexual characters.

(b) Sexual characteristics which develop in mature boys and girls are called secondary sexual characters.

Q.17. Name any two glands which function as endocrine glands as well as exocrine glands.

Testes and ovaries function as endocrine glands as well as exocrine glands.

Q.18. What is the other name of ductless glands?

Endocrine glands are also known as ductless glands.

Q.19. What term is used for the secretion of endocrine glands?

The secretion of endocrine glands is known as hormones.

Q.20. Name:
(a) female sex hormone, and
(b) male sex hormone.

(a) Estrogen

(b) Testosterone

Q.21. Name the hormone which develops secondary sexual characteristic:
(a) in females (girls).
(b) in males (boys)

(a) Estrogen

(b) Testosterone

Q.22. State the function of male sex hormone ‘testerone’.

The function of male sex hormone ‘testosterone’ is to develop secondary sexual characters in the boys.

Q.23. Name the endocrine gland which controls the production of sex hormones ‘testosterone’ and ‘estrogen’.

The production of sex hormones ‘testosterone’ and ‘estrogen’ is under the control of another hormone secreted from an endocrine gland called pituitary gland.

Q.24. What is the name of the process in which the thickened uterus lining along with its blood vessels is removed from the body of a woman through vaginal bleeding?

The process in which the thickened uterus lining along with its blood vessels is removed from the body of a woman through vaginal bleeding is called menstruation.

Q.25. Which comes earlier in the life of a woman: menarche or menopause?

Menarche comes earlier in the life of a woman.

Q.26. (a) Around which age menarche occurs in girls ?
(b) Around which age menopause occurs in woman?

(a) At puberty (10 to 12 years of age).

(b) At 45 to 50 years of age.

Q.27. State one situation (other than menopause) when ovulation and menstruation stop in a woman.

When a woman is preganant.

Q.28. Which of the two has a shorter reproductive phase of life: men or women?

Women has a shorter reproductive phase of life.

Q.29. Which of the following combinations of sex chromosomes products a male child (or boy)?
XX or XY

XY combination of sex chromosomes produces a male child (or boy).

Q.30. Which of the two, sperm or egg cell (ovum), decides the sex of the child?

Sperm decides the sex of the child.