Lakhmir Singh & Manjit Kaur: Reaching The Age Adolescence- 2 | Lakhmir Singh & Manjit Kaur Solutions: Class 8 Science PDF Download

Q.31. What is the legal age for the marriage of (a) boys, and (b) girls, in our country?

The legal age for the marriage is (a) 21 years for boys, and (b) 18 years for girls in our country.

Q.32. Name a natural balanced food for infants.

Mother’s milk is a natural balanced food for infants.

Q.33. During which time the adolescent girls should take special care of personal hygiene?

The adolescent girls should take special care of personal hygiene during the time of menstrual flow.

Q.34. Write the full name of
(i) AIDS, and
(ii) HIV.

(i) AIDS stands for Acquired Immunodeficiency Syndrome.

(ii) HIV stands for Human Immunodeficiency virus.

Q.35. Write the name of the virus which causes AIDS disease.

HIV virus causes AIDS disease.

Q.36. Name the endocrine gland attached to the base of brain.

Pituitary gland is attached to the base of brain.

Q.37. Name the endocrine gland which secrets the growth hormone.

Pituitary gland secrets the growth hormone.

Q.38. Name the substance which is needed continuously by thyroid gland to make thyroxine hormone.

Iodine is needed continuously by thyroid gland to make thyroxine hormone.

Q.39. State the main symptom of goiter.

The main symptom of goiter is a very big and bulging throat.

Q.40. Name the hormone whose deficiency in body causes goiter.

The deficiency of thyroxine hormone in body causes goiter.

Q.41. Name the gland which secretes insulin hormone.

Pancreas secretes insulin hormone.

Q.42. Name the disease caused by the insufficient production of insulin hormone by pancreas.

The disease caused by the insufficient production of insulin hormone by pancreas is diabetes.

Q.43. Name the hormone which prepares our body for action to face emergency situation like danger, fear, anger or excitement.

Adrenaline hormone prepares our body for action to face emergency situation like danger, fear, anger or excitement.

Q.44. Name the endocrine gland which secretes hormone that maintains correct salt balance in the blood.

Adrenal gland secretes hormone called aldosterone that correct salt balance in the blood.

Q.45. Name a hormone (other than adrenalin) secreted by adrenals.

Aldosterone hormone is also secreted by adrenals.

Q.46. Name the hormone whose deficiency causes diabetes.

Insulin hormone deficiency causes diabetes.

Q.47. Name the hormone which is required for the metamorphosis of larvae (tadpoles) into adult frogs.

Thyroxine hormone is required for the metamorphosis of larvae (tadpoles) into adult frogs.

Q.48. Name the hormone which brings about metamorphosis in silk moth and changes caterpillar (larva) into adult silk moth.

Insect hormone brings about metamorphosis in silk moth and changes caterpillar (larva) into adult silk moth.

Q.49. State whether the following statements are true or false:
(a) The estrogen hormone develops deeper voice in males at puberty.
(b) Menstruation stops in men permanently around the age of 45 to 50 years.
(c) Man (father) is responsible for the sex of the body.
(d) The sex chromosomes in all the gametes (sperms) of a man are not identical.
(e) Half the female gametes contain X chromosomes and the other half contain Y chromosomes.
(f) It is the sperm which determines the sex of a child.
(g) Each normal cell in our body contains 23 chromosomes and the other half contain Y chromosomes.
(h) A girl should not be allowed to work in the kitchen during menstruation.
(i) A woman (mother) is responsible for the sex of her child.
(j) Metamorphosis in insects (like silk moth) is brought about by thyroxine hormone.

(a) False, the estrogen hormone is a female hormone secreted by ovaries.

(b) False, menstruation stops in woman permanently around the age of 45 to 50 years.

(c) True, Man (father) is responsible for the sex of the body.

(d) True, the sex chromosomes in all the gametes (sperms) of a man are not identical.

(e) False, female gametes contain only X chromosomes.

(f) True, Sperm determines the sex of a child.

(g) False, each normal cell in our body contains 23 pair of chromosomes.

(h) False, it is a myth and not facts. A girl should not be allowed to work in the kitchen during menstruation.

(i) False, man is responsible for the sex of his child.

(j) False, Metamorphosis in insects (like silk moth) is brought about by insect hormone.

Q.50. Fill in the following blanks with suitable words:
(a) Sexual maturity is reached at _________.
(b) The changes which occur in boys and girls at puberty are brought about by various _________.
(c) Initially, girls grow _________ than boys.
(d) The changes occurring in body and mind during adolescence are a natural part of _________ up.
(e) The features which help us to distinguish between a mature boy and a girl are called _________ sexual characteristics.
(f) The onset of puberty is controlled by_________.
(g) Menstrual cycle in women is controlled by_________.
(h) Each normal body cell in humans contains _________ pairs of chromosomes out of which _________ pair is of sex chromosomes.
(i) X and Y chromosomes are called _________ chromosomes.
(j) Early marriage and motherhood cause health problems in the _________ and the _________.
(k) The protective foods are _________ And _________.
(l) Thyroid and adrenals secrete their hormones when they receive instructions from _________ gland through its hormones.
(m) Metamorphosis in amphibians is brought about by _________ hormone.

(a) puberty
(b) hormones
(c) faster
(d) growing
(e) secondary
(f) hormones
(g) hormones
(h) 23 ; 1
(i) sex
(j) mother; child
(k) fruits; vegetables
(l) pituitary
(m) thyroxine

Q.51. Define adolescence. State some of the change which take place in boys and girls during adolescence.

The period of life, when the body undergoes changes, leading to reproductive maturity, is called adolescence. Adolescence begins around the age of 11 and lasts upto 18 or 19 years of age.
The changes which take place in boys are facial and body hair growth, voice deepens, testes start to make sperms etc.
The changes which take place in girls are breast grow, ovaries start to release egg, menstruation begins etc.

Q.52. What is puberty? Who attains puberty at an earlier age in human beings: male (boy) or female (girl).

The age at which the sex hormones and gametes begin to be produced and the body and the girl become sexually matured is called puberty.
Generally girl attains puberty at an earlier age (11 to 12 years) in human beings.

Q.53. Write two changes that happen during puberty to: (a) both boys and girls (b) boys only (c) girls only.

(a) (i) There is a sudden increase in the height of both boys and girls during puberty.

(ii) Development of sex hormones also take place in both boys and girls during puberty.

(b) Changes that place only in boys during puberty are:

(i) Growth of hairs on chest.

(ii) Enlargement of voice box which leads to much deeper voice

(c) Changes that place only in girls during puberty are:

(i) Mammary gland enlargement

(ii) Menstruation.

Q.54. (a) State two ways in which the body shape of boys changes during puberty.
(b) State two ways in which the body shape of girls changes during puberty.

(a) The changes in body shape of boys during puberty occur in following ways:

• In boys, shoulder become broad and chest become wide.
• In boys, the muscles of the body grow more prominently than in the girls.

(b) The changes in body shape of girls during puberty occur in following ways:

• In girls, the region below the waist becomes wider.
• Girls have high pitched voice.

Q.55. State one change in the body shape of grown up boys and one changes in the body shape of grown up girls which makes them look different.

In boys, the muscles of the body grow more prominently than in the girls. Whereas In girls, the region below the waist becomes wider. Thus, The changes in adolescent boys and girls are different.

Question 56 (a) What is the effect of a larger voice box in grown up boys?
(b) What is the effect of a smaller voice box in grown up girls?

(a) Voice box is also known as larynx. In adolescent boys, voice box begins to grow and becomes large. Because of larger voice box, the voice becomes hoarse in grown up boys.

(b) In girls, larynx is small in size due to which they have a high pitched voice.

Q.57. What is Adam’s Apple? Which of the two usually have an Adam’s Apple: grown up boys or grown up girls?

In adolescent boys, voice box can be seen a protruding part of the throat called Adam’s apple. Grown up boys usually have an Adam’s apple.

Q.58. What change in the voice of body takes place when they reach puberty? What is the cause of this change?

When a boy reaches puberty, then his, voice box (also known as larynx). In adolescent boys, voice box begins to grow and becomes large. Because of larger voice box, the voice becomes hoarse in grown-up boys.

Q.59. (a) Name two male sex organs and two female sex organs which develop completely at puberty.
(b) Name two things which may develop on the face of adolescent boy s and girls during puberty due to the increased activity of sebaceous glands and sweat glands in the skin.

(a) At puberty, male sex organs like the testes and penis develop completely. In girls, female sex organs like ovaries and uterus develop completely.

(b) Many adolescent boys and girls may get acne and pimples on the face during puberty due to the increased activity of sebaceous glands and sweat glands in the skin.

Q.60. (a) State two secondary sexual characteristics in mature boys and two in mature girls.
(b) Which of the following are secondary sexual characteristics
Ovaries, Moustache, Penis, Broad hips, Vagina, Beard, Breast, Adam’s Apple, Wide shoulders, uterus, Testes, Deeper voice.

(a) (i) Secondary sexual characteristics in mature boys:

• Voice becomes deeper (low pitched voice).
• Facial hair such as beard and moustache develop.

(ii) Secondary sexual characteristics in mature girls:

• Development of breast.
• Initiation of menstrual cycle.

(b) Moustache, broad hips, beard, breast, Adam’s apple, wide shoulders and deeper voice are secondary sexual characteristics whereas ovaries, penis, vagina, uterus and testes are primary sexual characteristics.