Reaching the age of adolescence class 8 science study material .pdf

6 REACHING THE AGE OF
ADOLESCENCE
6.1
6.2
6.3
6.4
The endocrine
system
Puberty
Menstrual cycle
Reproductive
health
6.1 THE ENDOCRINE SYSTEM
The endocrine system regulates biological processes through the release of
chemicals called hormones. The major function of the endocrine system is
to participate in maintaining homeostasis. It is also involved with growth,
development and adaptation. Within all of these changing processes, our
bodies tolerate fluctuations within certain limits but still overall
homeostasis needs to be maintained.
Hormones are released into body fluids—usually blood, which carries these
chemicals to their target cells, where they elicit a response. The responses
elicited by hormones usually take several seconds to several days to occur.
Hormones of the endocrine system can regulate functions of the body on
longer time scales to maintain homeostasis.
The different endocrine glands are as follows:
PITUITARY GLAND is a pea-sized gland located at the base of the brain
attached to the hypothalamus via a stalk called the infundibulum. The
pituitary gland is primarily regulated by nerve impulses or hormones
released from the hypothalamus. The pituitary, in turn, releases hormones
that either have a direct effect on target cells or regulate hormone
production by other endocrine glands thus, they are also addressed as the
“master gland”.
Associated hormones Main effect
Growth hormone Promotes growth of body tissues
Thyroid-stimulating
hormone (TSH)
Stimulates thyroid hormone release
Adrenocorticotropic
hormone (ACTH)
Stimulates hormone release by adrenal
cortex
Follicle-stimulating
hormone (FSH)
Stimulates gamete production
Luteinizing hormone
(LH)
Stimulates androgen/estrogen production by
gonads
THYROID GLAND is located in the neck, just below the larynx. It
possesses two lobes and has a dark red color due to its extensive
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vasculature. When the thyroid increases in size due to dysfunction, it can be felt under the skin of the
neck. The main function of the thyroid gland is the synthesis and storage of the thyroid hormones,
thyroxine and calcitonin that are involved in maintaining metabolic homeostasis.
The four PARATHYROID GLANDS are each the size of a grain of rice and are usually located on the
posterior surface of the thyroid gland. Calcitonin, along with the parathyroid hormone, regulates the level
of calcium and phosphorus in blood.
ADRENAL GLANDS help regulate the body’s response to stress, controlling blood pressure, and
maintaining the body’s water, sodium, and potassium levels. The adrenal glands sit on top of each kidney.
They consist of an outer adrenal cortex (cortex means outer layer) and an inner adrenal medulla (medulla
means middle).
Adrenal
cortex
Aldosterone Increases blood Na+
levels, and related water conservation
by kidneys, Decreases blood K+
levels
Corticosteroids Increase blood glucose levels
Adrenal
medulla
Epinephrine, norepinephrine Stimulate fight-or-flight response
PINEAL GLAND is located between the cerebral hemispheres of the brain. It consists of secretory cells
that secrete the hormone melatonin which regulates the sleep cycle.
PANCREAS is an elongated organ that plays a central role in energy metabolism, storage, and utilization
of glucose (carbohydrate). It is located slightly dorsal to the stomach and between the stomach and the
small intestine. It releases glucagon (increases blood glucose levels) and insulin (decreases blood glucose
level). Deficiency in insulin can lead to diabetes.
GONADS, the male testes and female ovaries, function in production of gametes (sperm and ovum) and
also produce hormones. The testes produce testosterone that stimulates the development of male
secondary sex characteristics and the production of sperm cells. The ovaries produce the hormones
estrogen and progesterone, which stimulate the development of female secondary sex characteristics,
regulate the menstrual cycle, and prepare the body for childbirth.
HYPOTHALAMUS
The hypothalamus is a portion of the brain that contains a number of small nuclei with a variety of
functions. One of the most important functions of the hypothalamus is to link the nervous system to the
endocrine system via the pituitary gland. Hypothalamic hormones stimulate or inhibit the secretion of
pituitary hormones. The hypothalamus controls body temperature, hunger, and important aspects of
parenting and attachment behaviors, thirst, fatigue, sleep and circadian rhythms.
Thyrotropin-releasing hormone Stimulates TSH release from pituitary
Corticotropin-releasing hormone Stimulates ACTH release from pituitary
Growth-hormone-releasing/inhibiting hormone Stimulates/inhibits growth hormone release from
pituitary
Gonadotropin-releasing hormone Stimulates FSH and LH release from pituitary

6.2 PUBERTY
The beginning of biological growth and development during adolescence is signified by the onset of
puberty, which is often defined as the physical transformation of a child into an adult. A myriad of
biological changes occur during puberty including sexual maturation, increases in height and weight,
completion of skeletal growth accompanied by a marked increase in skeletal mass, and changes in body
composition. The succession of these events during puberty is consistent among adolescents.
Puberty is initiated by hormonal signals from the brain to the gonads: the ovaries in a girl, the testes in a
boy. In response to the signals, the gonads produce hormones that stimulate libido and the growth,
function, and transformation of the brain, bones, muscle, blood, skin, hair, breasts, and sex organs.
Physical growth—height and weight—accelerates in the first half of puberty and is completed when an
adult body has been developed.
On average, girls begin puberty around ages 10–11 and end puberty around 15-17; boys begin around
ages 11–12 and end around 16-17. The major landmark of puberty for females is menarche, the onset of
menstruation, which occurs on average between ages 12–13; for males, it is the first ejaculation, which
occurs on average at age 13.
The following are the five chief physical manifestations of puberty:
1. A rapid acceleration in growth, resulting in dramatic increases in both height and weight.
2. The development of primary sex characteristics, including the further development of the gonads, or
sex glands, which are the testes in males and the ovaries in females.
3. The development of secondary sex characteristics, which involves changes in the genitals and breasts;
the growth of pubic, facial, and body hair; and the further development of the sex organs.
4. Changes in body composition—specifically, in the quantity and distribution of fat and muscle.
5. Changes in the circulatory and respiratory systems, which lead to increased strength and tolerance for
exercise.
Hormonal effects
Males Females
LH Testosterone production Androgen and Progesterone production
Ovulation
FSH Sperm production Ovarian follicle development
Estrogen production
Testosterone Growth of penis and scrotum
Growth of pubic/facial hair
Deepening of voice
Increased libido
Increased muscle mass
Acne
Thickening of cortical bone
Thickening of cortical bone
Growth of pubic hair
Estrogen Important bone effects:
Low levels: pubertal growth spurt, accrual
of peak bone mass
Higher levels: closure of the epiphyses
Bone effects as in males
Growth of breasts, labia, vagina, uterus
Pattern of fat deposition
Vaginal pH ↓and vaginal length ↑
Proliferation of the endometrium

Summary on the physical changes taking place during adolescence
Males Females
On an average, boys grow about 20 cm in height
between 13 to 15 years of age.
A girl gains about 8cm in height between 11 to
13½ years of age.
Develop a lot of muscles, enabling them to do
heavy physical work.
Develop more fatty and subcutaneous tissue giving
rise to rounded contours.
Boys develop broader and stronger shoulders while
their hips remain slender.
The shoulders are slender while hips become
broader and rounded.
Hair on the body becomes darker and curlier. Hair
appears in the armpits and pubic area. Facial hair
appears at side of the mouth, lips, cheeks and then
the sides of the face.
Hair growth in the arm-pits and pubic area.
The voice breaks i.e. becomes squeaky and
matures. This happens because the larynx enlarges
and vocal cord lengthens. Adam’s apple becomes
prominent.
The voice becomes more shrill and adult like.
Increase in the size of the penis. Appearance of the breast-bud.
First nocturnal emission occurs nearly a year after
the penis starts growing. The seminal fluid may not
contain sperms at puberty.
Onset of menarche or first menstrual cycle. First
few cycles may be irregular and sometimes painful.
PUBERTY AND MENTAL ILLNESS
Many mental disorders such as major depression, certain anxiety disorders, eating disorders and substance
use disorders increase in prevalence during adolescence. Puberty is a time of increasing stresses and
challenges, as children adapt to their changing social roles. For this reason, mental health issues often first
emerge in adolescence. Younger children and those with fewer social and emotional resources may find
this phase more difficult, which increases their risk of subsequent mental health difficulties.
In most animals and humans, the young ones directly grow into adults. However, in some like insects,
they undergo metamorphosis which is controlled by the insect hormones. For example, in frog,
metamorphosis is controlled by throxine. Iodine is an essential element for thyroxine production. If the
water where the tadpoles inhabit lack iodine, they can’t become adults.
6.3 MENSTRUAL CYCLE
Unlike males where sperms can be produced throughout the life of man, in females the reproductive
phase only lasts till the age of 45-50 years. This phase is characterized by the presence of menstrual cycle.
The menstrual cycle in women is a recurring process in which the lining of the uterus is prepared for
pregnancy, and if pregnancy does not happen, the lining is shed at menstruation. The cycle lasts about 28
days.

Several hormones control this cycle:
FSH, LH Estrogen, Progesterone
Secreted by Pituitary gland Ovaries
Function Control the release of egg from ovary Change the thickness of uterus lining
Each cycle has the following phases:
I. Menstrual phase: It lasts for the first 3-4 days. During this phase the inner lining of the uterus is shed
which causes the blood vessels to rupture. This causes bleeding and is called menstruation. The first
occurrence of mensuration is termed menarche. It stops by the age of 45-50 years and is called
menopause. In the ovary, during this phase, the follicles where the eggs are produced are growing.
Follicles are structures formed by the aggregation of the germinal epithelial cells of the ovary.
II. Follicular/Proliferative phase: In this phase, the follicles grow further. The FSH stimulates one of the
follicles. The stimulated follicle grows in size. One of the cells of this follicle becomes bigger and
separated from the rest by a follicular cavity. This cell becomes the egg. The outer layer of cells of this
follicle is called theca interna. This layer secretes a hormone called estrogen. This follicle is called the
Graafian follicle. This phase lasts from the 6th
- 10th
day. In the uterus, this phase sees the inner wall of the
uterus being built up again in order to receive the product of fertilization, if there is one. It is again
supplied with blood vessels.
III. Ovulatory phase: When the follicle is mature, the pituitary gland secretes another hormone called
luteinizing hormone (LH). LH stimulates the follicle to rupture and release the egg. The release of egg is
called ovulation and occurs between the 10th and the 16th day. The egg moves along the oviduct during
this time and may be fertilized by the sperm. If not, it starts disintegrating.
IV. Luteal/Secretory phase: This phase lasts between the 16th
and the 28th
day. Once the egg is released,
the Graafian follicle re-aggregates to form corpus luteum. The corpus luteum secretes two pregnancy
hormones - progesterone and relaxin. The degenerating corpus luteum is called corpus albicans. In the
uterus, its lining is thickened further. At the end of 28 days, if fertilization has not taken place, the lining
is shed along with the egg. This starts a new cycle all over again.
Phases of the menstrual cycle

SEX DETERMINATION IN HUMANS
We determine the sex with the help of the sex chromosomes i.e. X and Y chromosomes. In human beings
46 chromosomes are found out of which 44 are found in 22 pairs called autosomes and other two
chromosomes are called sex chromosomes. The rest two chromosomes are same in female and are called
X- chromosomes (XX). In male the rest two chromosomes are different and are called X and Y
chromosomes. During reproduction females produces one type of gametes and containing 22 autosomes
and one X chromosomes, while males produces two types of gametes one have 22 + X type chromosomes
and other have 22+ Y types of chromosomes. When a male gamete i.e. sperm carrying X chromosome
fertilizes an ova, the zygote develops into female. When a sperm carrying Y chromosomes fertilizes an
egg, zygote develops into male.
6.4 REPRODUCTIVE HEALTH
The World Health Organization (WHO) defines reproductive health as a state of complete physical,
mental and social well-being, and not merely the absence of reproductive disease or infirmity.
Reproductive health involves all of the reproductive processes, functions and systems at all stages of
human life. It is a fundamental component of an individual’s overall health status and a central
determinant of quality of life.
During adolescence, the need for proper nutrition and sound personal hygiene become highly essential.
As the body is growing, it needs a well-balanced diet for its maintenance. A balanced diet contains the
essential nutrients with a reasonable ration of all the major food groups. Likewise, cleanliness is an
essential factor that should be maintained otherwise it might lead to infections as severe as reproductive
tract infections. The best way to stay fit and fine is exercising daily. It helps regulate the hormones
properly and thereby, keeping the body healthy. Any deficiency of hormones during adolescence can lead
to retarded growth and disorders.

Solved Examples
Example 1
Why pimple and acne appear during adolescent period?
Solution
During adolescent period, both sweat glands and sebaceous glands become more active especially on the
face. Hence pimples and acne appear on face because of this.
Example 2
How are the secretions of ductless glands transported in the body?
Solution
Glands without ducts are termed as endocrine glands. These glands pour their secretions directly into
blood which transport them to the target organs in the body.
Example 3
What marks the end of adolescence?
Solution
Reproductive maturity marks the end of adolescence.
Example 4
What is Adam’s apple?
Solution
In boys at puberty, the voice box or larynx protrudes out in the throat region known as Adam’s apple.
Example 5
Mention some secondary sexual characteristics seen in girls at the time of puberty.
Solution
Growth of pubic hair, hair under arms, breast development and pelvis broadening are few secondary
sexual characters in girls.
Example 6
What would be the sex of the resulting baby when an egg gets fertilized by a sperm containing Y
chromosome?
Solution
Male
Example 7
What leads to diabetes?
Solution
Deficiency of insulin leads to higher sugar level in the blood causing diabetes.
Example 8
What personal hygiene should be observed by the teenagers?
Solution
It is very important for the teenagers to be careful about cleanliness as there is an enhanced activity of
sweat glands which makes the body smelly. Proper bathing and maintenance of hygiene is very
important to check infections. During menstrual flow girls should take special care about cleanliness, to

avoid various reproductive tract infections.
Example 9
What is the role of hormones in initiating reproductive function?
Solution
Hormones from pituitary stimulate testes and ovaries to release testosterone and estrogen respectively.
These sex hormones reach to target sites via blood and then stimulate changes in the body at the onset of
puberty.
Example 10
Discuss reproductive phase of life in women.
Solution
In females, the reproductive phase of life begins at puberty and continues till they reach the age of
45-50 years. The egg begins to mature with the onset of puberty. One mature ovum is released by one of
the ovaries every month. The process is called ovulation. During this period, the walls of the uterus
become thick so as to receive the fertilized egg. Then this egg gets implanted in the uterus resulting in
pregnancy.
Example 11
Give reasons for the following.
(a) Tadpoles growing in iodine deficient water have retarded growth.
(b) Voice becomes hoarse in adolescent boys.
(c) Females have no role in determining gender of a child.
Solution
(a) The process of growth and development is regulated by thyroxine hormone which is produced by the
thyroid gland. Iodine is required for thyroxine production. That is why retarded growth is seen in
tadpoles living in iodine deficient water.
(b) Sometimes the muscles of the growing voice box go out of control and the voice becomes hoarse.
(c) Y- chromosomes that lead to a boy offspring is contributed by male parent. That is the sperms are of
two types, having either X or Y chromosome.
Example 12
What are the causes of AIDS?
Solution
 Sharing needle of the syringe
 unprotected sex with infected person
 blood transfusion from infected person to healthy one
 infected mother can pass HIV through milk to an infant
Example 13
Write down the ways to maintain a healthy personal hygiene.
Solution
The basic aim of maintaining personal hygiene is to keep the bacteria and other harmful microorganisms
away from entering the body or infecting the food consumed by us. Otherwise, diseases can develop.
Following precautions need to be taken for maintaining personal hygiene:
 Before and after taking meals, always wash your hands with sap water.

 Clean your teeth after each mean and before going to bed. Otherwise tooth decay may take place.
 Take bath regularly with clean water.
 Do not grow long nails. Keep them short and clean.
 The feet should be cleaned and well protected. Injuries due to bacterial like tetanus, hookworms and
insects may be caused if barefoot walk is undertaken. Walking barefoot must be avoided.
 Hairs should be cleaned regularly with soap and water. Combing removes the dirt sticking to hair.
 Eyes should be washed daily with clean and cold water. Rubbing of eyes with hands should be
avoided to prevent the entry of germs into the eyes.
 The waste food material and garbage should be disposed off properly. It should not be thrown in the
open. Covered bins must be employed.
Example 14
What is menstruation? Explain.
Solution
The bleeding that occurs from the uterus once in a month in women is called menstruation. During
menstruation, the uterus along with blood vessels breaks off. This causes blood to come out and a new
wall of the uterus is formed. Menstruation generally lasts for 4-5 days.
Example 15
Complete the following sentences.
(a) Adolescents should be careful about what they eat because ___________.
(b) Reproductive age in women starts when their ___________.
(c) The right meal for adolescents consists of ___________.
Solution
(a) proper diet is needed for the rapid growth taking place in their body.
(b) menstruation starts.
(c) chapatti, dal and vegetables.
******

EXERCISE
 Multiple choice questions with one correct answer
1. Puberty lasts till
(A) 10 years (B) 12 years (C) 13 years (D) 19 years
2. At puberty a diet rich in proteins is essential for
(A) supplying sufficient energy
(B) formation of new cells for growth
(C) formation of strong bones and teeth
(D) protection from diseases
3. Facial hair in boys is called
(A) secondary sexual
character
(B) adolescence (C) puberty (D) primary sexual
character
4. The pituitary gland controls
(A) hypothalamus (B) thyroid gland (C) pineal gland (D) all the glands
5. The belief that the mother is completely responsible for the sex of the child is wrong because the child
(A) gets sex chromosome only from the mother.
(B) develops in the body of the mother.
(C) gets one sex chromosome from the mother and the other from the father.
(D) gets sex chromosome only from the father.
6. AIDS can spread from an infected person to another person through
(A) sharing food (B) blood transfusion (C) sharing comb (D) a mosquito bite
7. The hormone secreted by pineal body is
(A) adrenaline (B) melatonin (C) growth hormone (D) insulin
8. Adams apple is
(A) enlarged mammary
gland
(B) enlarged larynx (C) apple of Adam (D) thyroid gland
9. A person was losing weight even though he was taking his meals regularly. He felt thirsty all the time.
His urine test showed high concentration of glucose. What may be the disease?
(A) Goitre (B) Cancer (C) Diabetes mellitus (D) Cirrhosis of liver
10. The information given below refers to the hormone.
I. Secreted by endocrine glands located on top of kidneys
II. Converts glycogen into glucose
III. Helps the body to adjust to stress
(A) adrenaline (B) insulin (C) progesterone (D) testosterone

11. Given below are events that lead to pregnancy and development of embryo.
(i) Fertilization of egg
(ii) Maturation of egg
(iii) Release of egg
(iv) Embedding of embryo in thickened uterine wall.
Which of the following options gives the correct order of sequence in which they occur?
(A) i, ii, iii, iv (B) ii, i, iii, iv (C) i, iv, ii, iii (D) ii, iii, i, iv
12. The most conspicuous visible change that occurs in boys during puberty is -
(A) development in voice box
(B) increase in height
(C) production of sperms
(D) increased sweating
13. At about the 14th day of menstrual cycle, a mature egg is released from an ovary. This is known as
(A) attraction (B) fertilization (C) menstruation (D) ovulation
14. For the metamorphosis of tadpoles which of the following elements must be available in water?
(A) chlorine (B) carbon (C) sulphur (D) iodine
15. The girl has menstruation on the 6th day of the month. When will ovulation most likely occur?
(A) 15-17th
day (B) 18-20th
day (C) 23-25th
day (D) 27-28th
day
16. Structures present in a cell which is responsible for determination of the sex of a baby is
(A) cytoplasm (B) cell membrane (C) nucleus (D) chromosome
17. Insufficient production of insulin in human body causes
(A) Myxoedema (B) Addison’s disease (C) Diabetes (D) Cretinism
18. What is the function of parathyroid hormone?
(A) regulates Ca level in the blood
(B) regulates phosphorus level in the blood
(C) regulates potassium level in the blood
(D) both (A) and (B)
 Fill in the blanks
19. ___________ determine the sex of an organism.
20. The ___________ gland is located at the base of the brain.
21. Testis produce ___________ and ovary produce ___________ and ___________ hormones.
22. ___________ is the main link between endocrine system and nervous system.
23. The uterus is thickened with ___________ during menstrual cycle.
24. AIDS and Syphilis are caused by ___________ and ___________.

25. Endocrine glands are also called ___________ glands.
26. The female is in the reproductive phase between ___________ and ___________.
27. The ___________ gland is present at the base of the throat in the neck.
 True or False
28. Hormones are called chemical messengers.
29. Thyroxine is produced by the pituitary gland.
30. Stoppage of menstruation in females is called menopause.
31. AIDS causes a disease termed as HIV disease.
32. Adolescence is marked by the onset of puberty.
33. It is the sperm which determines the sex of a child.
34. Drugs are addictive and should be avoided.
35. The estrogen hormone develops a deeper voice in males at puberty.
36. Fertilisation is necessary for asexual reproduction also.
 Solve the following
37. The sudden and noticeable changes begin in human during what phase of life?
38. What is hormone? Name different types of hormones in male and female along with their associated
glands.
39. Name the hormone that is released by testes at the onset of puberty.
40. Name the following.
(a) The period of life when the body undergoes changes leading to reproductive maturity is called -
(b) The voice box is also known as -
(c) Which of the following glands secrete oil?
(d) The first menstrual flow at puberty in females is termed as -
(e) Acne and pimples on the face are due to secretion of -
(f) Which of the following is the male hormone that is secreted by the testes at the onset of puberty?
(g) The female hormone secreted by the ovaries at the onset of puberty is -
(h) Adam’s apple is prominent in -
(i) When a sperm containing Y chromosome fertilises an egg with X chromosome, the zygote develops
into a _________ child.
(j) Hormones are secreted by -
(k) The maximum increase in height takes place during –
41. What do you mean by balanced diet?
42. Why pituitary gland is called ‘master endocrine gland’?

43. Mention the diseases caused by deficiency of different hormones.
44. What are the changes in shape of the body of girls and boys during adolescence?
45. Explain the changes occurring in the voice of boys and girls during puberty.
46. During adolescence, the body of boys and girls undergoes certain changes. Given below are a few of
those changes.
(a) Broad shoulders
(b) Wider chests
(c) Wider region below waist
(d) Development of muscles
(e) Development of mammary glands
(f) Growth of facial hair
(g) Acne and pimples on face
(h) Development of sex organs
(i) High-pitched voice
(j) Growth of pubic hair.
Categorise these changes into those that occur in boys and those that occur in girls and fill in the table
given below.
47. Name the female hormone produced by ovaries that helps in development of mammary glands.
48. What are chromosomes? How many chromosomes are present in human being and rabbit?
49. Match the following.
Column 1
(a) XX
(b) Pancreas
(c) Endocrine gland
(d) High-pitched voice
(e) Puberty
Column 2
(p) Hormones
(q) Adolescence age
(r) Female
(s) Girls
(t) Insulin
50. A few of Sruti’s classmates eat potato chips and burgers regularly during the recess at school. Are they
healthy eating habits? Give reasons.
51. How can bad habits like drug addiction harm young people?
52. We should avoid taking medicines/drugs unless prescribed by a doctor. Give reasons
53. Mention any two features each that are seen in boys and girls each to distinguish them from each other at
puberty.
54. In human females, each time during maturation and release of egg the inner wall of uterus thickens. Is
this thickening permanent? Give reasons.
55. Name the endocrine glands which release the hormones that -
(a) controls the release of sex hormones.

(b) is responsible for the secondary sexual characters in boys.
(c) prevents diabetes.
(d) maintains the correct salt balance in the blood.
56. Write down the factors affecting the height of a person.
57. Match the following.
Hormones
(a) Insulin
(b) Thyroxine
(c) Adrenaline
(d) Growth hormone
Glands
(p) Adrenal gland
(q) Pancreas
(r) Pituitary gland
(s) Thyroid
58. What is the role of hormone in the completion of life history of insects and frogs?
59. Read the statements given below and fill up the blanks with the correct words listed -
[deep, ductless, nutrients, thyroxine]
(a) The meal that includes all __________ is a balanced diet.
(b) Insufficient production of __________ in the tadpoles leads to their incomplete development.
(c) Endocrine glands are also called __________ glands.
(d) After attaining puberty boys develop a__________ voice.
60. What is menstrual cycle? How many phases are there in this cycle? What are they?
61. Simmi had a very soft and smooth skin during her childhood. As she entered adolescence, she developed
pimples on her face. The skin specialist advised her to wash her face at regular intervals. Can you
explain the reasons for the appearance of pimples on her face and suggest ways to prevent them?
62. Unscramble the underlined words in the following sentences.
(a) Reproductive life of a woman lasts from hacreemn to spauoemen.
(b) The development of a caterpillar to an adult butterfly is termed as poommertaissh.
(c) The overgrowth of sumselc in xalnyr leads to the hoarse voice in adolescent boys.
(d) Danenalier helps the body to adjust and fight the stress.
63. What do you mean by health? What are the factors regulating good health?
64. What are the highlighting changes occurring in humans during puberty?
65. Describe in detail the sex determination of human baby.
66. Give a suitable word for each of the following statements.
(a) The site which responds to a hormone.
(b) Name of a gland which transports secretions through ducts.
(c) Chemicals which control changes at adolescence stage.
(d) It marks the beginning of reproductive period.
67. Sneha always eats only dal and rice in every meal. She often falls ill and has become prone to diseases.
Can you suggest changes in her diet which can make her healthy and free from disease?

68. It is believed that height of a child depends upon the genes inherited from parents. However, it is often
seen that tall parents may have short children and vice-versa. Are there factors other than genes that can
cause these variations?
69. What are the hormones controlling the menstrual cycle. Describe them in detail.
70. Fill the blank circles in the figure and identify the sex of child M and N.
71. Name the hormone which would be released during the following situations:
(a) a frightened person.
(b) growth of a child to adult.
(c) development of caterpillar to moth.
(d) development of tadpole to frog.
72. Our government has legalised the age for marriage in boys and girls. Give reasons as to why one should
get married after a certain age.
******

Answers
1. (D) 2. (B) 3. (A) 4. (D) 5. (C) 6. (B)
7. (B) 8. (B) 9. (C) 10. (A) 11. (D) 12. (B)
13. (D) 14. (D) 15. (B) 16. (D) 17. (C) 18. (D)
19. Allosomes 20. pituitary 21. testosterone, estrogen, progesterone
22. Hypothalamus 23. blood vessels 24. HIV, Tryponema pallidum
25. ductless 26. menarche, menopause 27. thyroid
28. True 29. False 30. True 31. False 32. True
33. True 34. True 35. False 36. False
37. Adolescence 39. Testosterone
40. (a) Puberty, (b) larynx, (c) Sebaceous gland, (d) menarche, (e) oil glands during puberty, (f) Testosterone,
(g) Estrogen, (h) Adolescent boys, (i) Male, (j) Endocrine glands, (k) Adolescence
47. Estrogen 49. (a)-(r), (b)-(t), (c)-(p), (d)-(s), (e)-(q)
55. (a) pituitary gland, (b) testis, (c) insulin,
(d) thyroid gland
57. (a)-(q), (b)-(s), (c)-(p), (d)-(r)
59. (a) nutrients, (b) thyroxine, (c) ductless,
(d) high-pitched, deep
62. (a) menarche, menopause, (b) metamorphosis,
(c) muscles, larynx, (d) Adrenaline
66. (a) Target site; (b) Sweat glands/salivary glands/oil glands (any one); (c) Hormones; (d) Puberty
70.
71. (a) Adrenaline, (b) Growth hormone, (c) Insect hormones, (d) Thyroxine
******

Additional Notes for Competitive Exams
THE SEQUENCE OF PHYSICAL CHANGES AT PUBERTY
Boys Girls
Sex hormone levels are regulated by a
feedback system composed of gonads,
hypothalamus and pituitary glands.
Characteristic Age of First
Appearance
(Years)
Characteristic Age of First
Appearance
(Years)
Growth of testes,
scrotal sac
10-131/2
Growth of breasts 7-13
Growth of pubic
hair
10-15 Growth of pubic
hair
7-14
Body growth 101/2
-16 Body growth 91/2
-141/2
Growth of penis 11-141/2
Menarche 10-161/2
Change in voice
(growth of
larynx)
About the same
time as penis
growth
Underarm hair About two
years after
pubic hair
Facial and
underarm hair
About two
years after
pubic hair
appears
Oil- and sweat-
producing glands
(acne occurs
when glands are
clogged)
About the
same time as
underarm hair
Oil- and sweat-
producing
glands, acne
About the same
time as
underarm hair
PSYCHOSOCIAL PROCESSES AND THE SUBSTAGES OF
ADOLESCENT DEVELOPMENT
Substage Emotionally Related Cognitively Related Socially Related
Early
adolescence
Adjustment to a new body
image, adaptation to
emerging sexuality
Concrete thinking; early
moral concepts
Strong peer effect
Middle
adolescence
Establishment of emotional
separation from parents
Emergence of abstract
thinking, expansion of verbal
abilities and conventional
morality; adjustment to
increased school demands
Increased health risk
behavior; sexual interests in
peers; early vocational plans
Late
adolescence
Establishment of a personal
sense of identity; further
separation from parents
Development of abstract,
complex thinking;
emergence of post-
conventional morality
Increased impulse control;
emerging social autonomy;
establishment of vocational
capability

SOME GENETIC DISORDERS DUE TO CHROMOSOMES
Klinefelter Syndrome: When a male have an extra X or Y chromosome in sex chromosomes then the condition
will be XXY or XYY instead of XY. The individual became sterile in this condition. In female when an extra X
chromosome is present instead of XY they show normal development but limited fertility, mental retardness is
also seen in this type of syndrome.
Turner’s Syndrome: When a female has single sex chromosome (X0) their ovaries are rudimentary, lack of
secondary sexual character.
Down’s Syndrome: When an extra chromosome is added to the 21st
autosomal chromosome, it leads to Down’s
syndrome.
Colour Blindness: This disorder leads to failure to distinguish between red & green color. The gene responsible
for this disease is situated on a sex chromosome.
Number of Chromosomes in Different Organisms
Organisms No. of Chromosomes Organisms No. of Chromosomes
Pigeon 80 Cat 38
Dog 78 Frog 26
Horse 64 Pea 14
Chimpanzee 48 Tomato 24
Human 46 Wheat 42
Rabbit 44 Potato 48
REPRODUCTIVE TRACT INFECTION (RTI)
More commonly known as sexually transmitted infections, occur due to unhygiene. Few examples of RTI are –
SYPHILIS Cause: bacterium Treponema pallidum
Symptoms: a skin lesion, called a chancre, appears at the point of contact; it is classically
(40% of the time) a single, firm, painless, non-itchy skin ulceration with a clean base and
sharp borders.
Transmission: most commonly spread through sexual activity, kissing and close body
contact; it may also be transmitted from mother to baby during pregnancy or at birth.
Treatment: antibiotics
GONORRHOEA Cause: bacterium Neisseria gonorrhoeae
Symptoms: Many people have no symptoms. Men may have burning with urination,
discharge from the penis, or testicular pain. Women may have burning with urination,
vaginal discharge, vaginal bleeding between periods, or pelvic pain. Complications in
women include pelvic inflammatory disease and in men include inflammation of the
epididymis. If untreated, gonorrhea can spread to joints or heart valves.
Transmission: sexual contact with an infected person or by coming in contact with
infected clothes; can also spread from a mother to a child during birth.
Treatment: antibiotics

ACQUIRED
IMMUNODEFICIENCY
SYNDROME (AIDS)
Fast spreading incurable disease which weakens the immune system.
Cause: human immunodeficiency virus (HIV)
Symptoms: influenza-like illness i.e. cough, fever, loss of appetite, shortness of
breath, night sweat, severe weakness and then gradually weakens the immune
system, damages the brain, chronic diarrhea, loss of weight over a short time
Transmission: unprotected sexual intercourse with an infected partner; using
contaminated needles and syringes to inject drugs/vaccines; contaminated blood
transfusion; can pass from mother to child during pregnancy, delivery or
breastfeeding
Prevention: awareness among individuals; using condoms; not sharing needles
and others stuff and virtue of monogamy
******

Worksheet 1
1. Write the hormone secreted by the given glands. Also, mention their functions.
(a) Pituitary gland
(b) Pancreas
(c) Thyroid
(d) Adrenal
(e) Ovary
(f) Testes
2. Give reason why reproductive health is very important.

Worksheet 2
1. List the changes that take place in the boys during adolescence.
2. List the changes that take place in the girls during adolescence.
3. What is the difference between menarche and menopause?
4. Explain the role of personal hygiene and physical exercise for the growth of adolescents.

Answers
Worksheet 1
1. Gland Hormones Location Functions
(a) Pituitary Growth
hormone
Base of the brain Growth and development of the body
(b) Pancreas Insulin Near the liver Regulates the blood sugar level in the
blood. Deficiency causes diabetes.
(c) Thyroid Thyroxine Base of the throat Metabolism, growth and development.
Deficiency causes goitre.
(d) Adrenal Adrenaline Near the kidney Prepares the body for emergency situations
like fight, flight or fear; helps the body to
adjust to stress, etc.
(e) Ovary Oestrogen Pelvic region It controls the development of secondary
sexual characters in females.
(f) Testes Testosterone Male genital organs It controls the development of secondary
sexual characters in males.
2. Reproductive health is mainly regulated by the hormones. If a person is not healthy it results in
hormonal imbalance and becomes the reason for mental, emotional stress.
Worksheet 2
1. Broadening of shoulders, growth of facial hair and growth of hair in armpits and pubic area.
2. Development of breasts and growth of hair in armpits and pubic area.
3. The first menstrual flow that begins at puberty is menarche while the stoppage of menstruation at the
age of 45- 50 years is menopause.
4. Personal Hygiene: Adolescents show increased activity of sweat and sebaceous glands which may lead
to foul body odour. Therefore, it is important to maintain cleanliness and good personal hygiene. One
should take bath every day to avoid bacterial infections. Girls should take special care during
menstruation.
Physical Exercise: It is better for adolescents to enjoy some outdoor activities, such as walking,
jogging and other outdoor games. It improves their blood circulation and keeps them fit and healthy.
After all, a healthy mind resides in a healthy body.
******

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