Lakhmir Singh Manjit Kaur Class 8 Science 10th Chapter Reaching the age of adolescence Solution

Lakhmir Singh and Manjit Kaur Science solution: Reaching the age of adolescence Chapter 10. Here you get easy solutions of Lakhmir Singh and Manjit Kaur Science solution Chapter 9. Here we give Chapter 10 all solution of Class 8. Its help you to complete your homework.

Board – CBSE

Text Book – SCIENCE

Class – 8

Chapter – 10


1) Adolescent.

2) Teenagers.

3) 10-13 years and 18-19 years.

4) Rapid increase Height.

5) Rapidly.

6) Genes.

7) 160 cm.

8) Broader.

9) Broader.

10) Larynx.

11) Grown up girls.

12) Adam’s apple.

13) Oil, sebum.

14) Adolescent.

15) Sebaceous glands and sweat glants.

16) (a) Primary sexual characteristics.

(b) Secondary Sexual.

17) Testis, Ovaries.

18) Endocrine glands.

19) Hormones.

20) a> estrogen  b> testosterone.

21) a> estrogen  b> testosterone.

22) Produces sperm.

23) Pituitary Glands.

24) Menstruation.

25) Menarche.

26) a> 10-12 years.  b> 45-60 years.

27) Pregnancy.

28) Women.

29) XY.

30) Sperm.

31) a > 21 years   b> 18 years

32) Mother’s milk.

33) During menstruation.

34)  a> acquired immune deficiency syndrome,

b> Human immunodeficiency virus.

35) HIV.

36) Pituitary.

37) Pituitary.

38) Iodine.

39) The main symptom of goitre is swelling of the thyroid gland which causes a lump to develop in the throat.

40) Thyroxine.

41) Pancreas.

42) Diabetes.

43) Adrenaline.

44) Adrenal.

45)  Aldosterone.

46) Insulin.

47) Thyroxin.

48) Insect hormone.

49) a> False, b> False, c> True, e> False, f> True, g> False. h>False, i> False, j> False

50) a> Puberty, b> Hormones, c> Faster, d> Growing, e> secondary, f> Hormones, g> Hormones, h>23 ; 1


51) The transitional period of physical and metal development which occurs between childhood and adulthood is called Adolescence.

Some of changes which takes place in Boys during Adolescence are facial and body hair grow, Voice depends and testes start to make sperms and some of the changes which takes place in girls during adolescence are – Breasts grow, Ovaries start to release eggs and menstruation takes place.

52) The period during which adolescent boys and girls reach sexual maturity and become capable of reproduction is called Puberty.

Female attains puberty at an earlier age in human beings

53) a> Increase in height.

b>  Voice deepens in boys.

c> Hips of a girls broaden.

54) a> During puberty, hair grows on the face of boys. chest and shoulders of boys broaden.

b>  Breasts develop and enlarge in girls. Hips of girls broaden.

55) In boy, chest and shoulder of boys broaden. In girls, Hips of girls broaden and extra fat is deposited on hips and thighs.

56) (a) The low pitch voice is the effect of a larger voice box in grown up boys.

(b) The high pitch voice is the effect of a larger voice in grown up boys.

57) The bulge at the front of throat or neck in grown up boys is called Adam’s apple.

Grown up boys have an Adam’s apple.

58) When boys reach puberty, they have low pitch voice takes place in their voice.

At puberty, the voice box begins to grow in boys and the growth of voice box is much more than the growth of voice box in girls. This is the cause of voice changed,

59) (a) The two male sex organs are penis and testis and two female sex organs are ovaries and vagina develop completely at puberty.

(b) Pimples and Acne are the two things which may develop in adolescent boys and girls due to the increased activity of sebaceous gland and .sweat gland.

60)  (a) Two secondary sexual characteristics in mature boys are : Hair Grow on face and a deeper voice or low pitch voice.

(b) Two secondary sexual characteristics in mature girls are : development of breasts in girls and a shrill voice or high pitch voice.

61) The endocrine glands are : Pituitary gland, thyroid gland and adrenal glands.

62) a> The onset of menstruation in human female called ‘Monthly period’. In the age of 10-12 this occurs in human female.

b>  The permanent stoppage of menstruation in women called menopause. In the age of 45-50 this occurs in women.

63) Father is the responsible for the sex of the unborn child

This is because –

i) If a sparm carrying X chromosome fertilizers an egg cell which carries X chromosomes then the Zygote formed will have XX combination of sex chromosomes due to which the child born will be a girl.

ii) If a sperm carrying Y chromosomes fertilizers and egg cell which carries X chromosomes then the zygote formed will have X and Y combination of sex chromosomes due to which the child born will be a boy.


a> XX – Girl.

b> XY- Boy.

65) The chemical substance which co-ordinate the activities of living organisms and also their growth are called  hormones.

The hormones are made in some glands in our human body such as Pituitary gland, Thyroid gland and adrenal glands.

66) A hormone which is affecting sexual development or reproduction is called sex hormones.

The Two sex hormones are Estrogen and testosterone.

67) (i) The First occurrence of menstruation at puberty is called menarche.

(ii) The permanent stoppage of menstruation in a women is called menopause.

68) The bleeding from the uterus which occurs in a woman every month is called menstrual flow or menstruation.

With the onset of puberty, the eggs begin to mature in the ovaries of a woman. One mature egg is released by one of the ovaries of the woman in about  28-30 days. In the case of fertilization of egg cell occurs by a sperm, the fertilize egg cell begins to divide to an embryo. If fertilization does not occur, then the egg released by ovary dies within a few days and thick lining breaks down. Since the thick uterus lining contains a lot of blood vessels.

69) The sex of baby is determined by the of sex chromosomes present in the fretilised egg for the baby develops.

The two types of sex chromosomes are X and Y.

70) Sex is determined in the unborn child are given below :

  • If a sperm carrying X chromosome fertilizes an egg cell which carries X chromosome then the zygote formed will have XX combination of sex chromosomes due to which the child born will be a girl.
  • If a sperm carrying Y chromosome fertilizes an egg cell which carries X chromosome, then the zygote formed will have XY combination of sex chromosomes due to which the child born will be a boy.

71) The various ways that AIDS virus can be transmitted are :

  • Sharing of syringes used for used for injecting.
  • A healthy person can be effected through sexual contact with a person infected with HIV
  • Can be transmitted to an infant from infected mother through her milk.

72)  Some people use injections to take drugs. When an infected person sharing his injection to a healthy person then the healthy person is also effected with HIV virus. This is how, the uses of drugs helps in spreading AIDS disease.

73) The harmful effects of taking drugs are :

  • Drugs are addictive. If you take drugs once, you feel like taking them again and again.
  • Drug addicts become irritable and lose interest in their studies and job.
  • Drugs do physical harm to the body also drug can damage brain, liver and kidney etc.

74) Growth hormone.

Function of Growth Hormone:- The growth hormone controls the growth of the human body.

75) People are advised to use iodise salt for cooking food so as to prevent goitre disease. Iodise salt contains appropriate amount of iodine compounds. Iodised salt can provide all the iodine needed by Thyroid gland to make sufficient Thyroxine hormone for our body.

76) The deficiency of thyroxin hormone causes a disease known as goite.

The deficiency of the thyroxin hormone is the main causes goite.

77) Insulin.

The gland which secrets this hormone are Pancreas.

78) Insulin.

The Function of insulin hormone is to lower the blood sugar level.

79) The function of adrenaline hormone in our body to function at maximum efficiency during emergency situations such as danger, fear, shock etc.

80) The six endocrine glands are :

  • Pancreas : insulin.
  • Adrenal gland :
  • Testes : testosterone.
  • Ovaries : estrogen.
  • Thyroid gland : thyroxin.
  • Pituitary gland : growth hormone.

81) The following glands located in the human body are :

  • Pituitary : to the base of the brain.
  • Thyroid : in the neck
  • Pancreas : below the stomach
  • Adrenals : top of the two kidneys.

82) If this happen, then there will be deficiency of thyroxin hormone and they cannot undergo metamorphosis and hence cannot become adult frogs.

83) Acne is pink / black color spot which is formed on the skin on young boys face due to the increased activity of sebaceous gland and sweat glands present in the skin.

84) Pimples are small red spots on the face of a person.

Pimples are caused by the clogged and infected skin pores.

85) a> wheat , rice, sugar

b> Butter , Mustard oil, fatty meat

c>  Beans, Pulses, eggs

d>  Orange, milk

86) Iron mineral needed in our body for making blood in our body.

Iron-rich foods are : leafy vegetables, spinach, Indian gooseberry etc,

87) (i) Adolescene boys and girls should take bath regularly.

(ii) Adolescent girls should take special care of cleanliness of the body during the time of periods.

88) It is necessary for adolescents because the increased activity of sweat glands and oil glands makes the body smelly.

89) If not maintained, there are chances of catching bacterial infections.

90) The various ways in which early marriage and motherhood is harmful to the girls are following-

(i) The girls younger than 18 years of age aren’t prepared physically or mentally for motherhood.

(ii) Early marriage and motherhood cause health problems in the mother and the child.

(iii) Early marriage or motherhood can cause agony to the girls as she is not prepared to fulfill the responsibility of motherhood.

Long answer Type Questions Answer

91) a> Changes during puberty in Boys :

1> voice deepens in boys.

2> testes start to make sperms.

3> Testes and Penis become larger.

b> Changes during Puberty in girls :

1> Breasts develop and enlarge in girls

2> Ovaries start to release eggs.

3> Menstruation begin.

92) (a) The sexual Characteristics which are present at birth at birth are called primary sexual characteristics.

Two Primary sexual characteristic in boys are : Testes, Penis

Two Primary sexual characteristic in girls are : Ovaries, Uterus.

(b) The sexual characteristics controlled by hormones which distinguish between sexually mature males and females but are not directly involved in reproduction are called Secondary sexual characteristic.

In Secondary sexual characteristics the body develops special feature which make it easier to distinguish a boy from a girl. For example the growth of facial hair in Boys is a secondary sexual characteristics. Similarly the development of breast in a girl is a secondary sexual characteristics.

93) The process of ovulation and menstruation in women is called menstrual cycle.

The menstrual cycle is a period of about 28 – 30 days during which an egg cell matured. The matured egg cell is released by the ovary thickening of uterus linning takes place and finally the uterus linning breaks down causing bleeding in women. Menstrual cycle in women is controlled by hormones.

The duration is about 3 – 5 days.

94) a> Exocrine glands are glands that produce and secrete substances onto an epithelial surface by way of a duct.

Pancreas,thyroid are two exocrine glands.

b> Endocrine glands are ductless glands which pour their secretion directly into blood.

Hypothalamus, Pituitary gland are two endocrine glands.

95) a> The reproductive health contains the correct amount of each constituent sufficient for the normal growth and development of the body and keep a person healthy is called reproductive health.

b> Their are various condition necessary to maintain good reproductive health. Here some are point out below-

  • It is necessary to eat balance diet.
  • It is necessary to maintain personal hygiene.
  • It is necessary to take adequate physical exercise.

Higher Order Thinking Skills (HOTS)


The process of ovulation and menstruation is called menstrual cycle. The menstrual cycle is a period of about 28 to 30 days. At the end of this cycle the inner lining of the uterus breaks down which produces blood and other tissues. This blood and other tissues from uterus come out of vagina of women in the form of bleeding. The scientific name of this process is called menstruation however in everyday language it is known as periods.  The menstrual cycle starts in female body when they have attained puberty. This indicates that reproductive system of the female body has started working. This cycle continues every month unless the egg cell is not fertilized. When the egg cell is fertilized the menstrual cycle stops and marks the start of pregnancy. The stoppage of menstruation cycle in a woman is called menopause.


When a woman reaches in her reproductive phase of her life only then she can get pregnant. However, there are some difficulties for which a woman might not be able to bear a baby. When the sperms are available at the time of release of a mature ovum by the ovary but the fertilization does not take place then there might be some problem. One of the common problems that may be behind this is the blockade of the oviducts of woman.If the oviducts of a woman are blocked then she can have a baby through IVF or In Vitro Fertilization. In vitro fertilization is a process of fertilization where an egg is combined with sperm in a test tube.


Rajkumar and his wife sunita have been blessed with a baby girl. Rajumar has XY sex chromosomes and Sunita has XX sex chromosomes. Their baby girl has XX Chromosome. Rajumar contributed X chromosome and Sunita also contributed X chromosome in the XX sex chromosomes of their baby girl.

Kripa Shankar and his wife Vimla has been blessed with a baby boy.Kripashankar has XY chromosomes and his wife vimla has XX sex chromosomes. KripaShankhar contributed Y chromosomes and Vimla contributed X chromosomes in the XY sex chromosomes of their baby boy.


W = Pancreas

X = Insulin

Y = Diabetes

Z = Diabetic

Pancreas (W) is an important gland located just below the stomach in the human body. Pancreas secretes a hormone called Insulin (X). The deficiency of insulin in the body causes Diabetes (Y) in which the blood sugar level of a person rises too much. The person who has high blood sugar is called diabetic (Z).


P = Iodine

Q = Thyroxin

R = Metamorphosis

It can be observed sometimes that tadpoles in a pond are not growing into adult frogs. If investigated by a scientist it will be discovered that the pond does not contain enough amount of Iodine (P) which could make a hormone Thyroxin (Q). Thyroxin causes metamorphosis (R) in tadpoles so that they become adult frogs. The deficiency of Iodine in humans can cause Goitre.

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  1. I see each an every science chapter from here, I am from class 8, it helps me everytime…Tomorrow is my science exam and here we go again! Tysm

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