## PSEB Solutions for Class 8 Science Chapter 10 Reaching the Age of Adolescence

PSEB 8th Class Science Guide Reaching the Age of Adolescence Textbook Questions and Answers

Exercises

Question 1.
What is the term used for secretions of endocrine glands responsible for changes taking place in the body ?
Hormones.

Question 2.
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 adolescents are also called “teenagers”. Adolescence in girls may begin a year or two earlier than in boys. Also the period of adolescence varies from person to person.

Question 3.
WTaat is Menstruation ? Explain.
Menstruation.
The rhythmic changes in the uterus which occur about every 28 days throughout the reproductive cycle of women except the pregnancy is called menstrual cycle. The female sex hormones initiate the thickening of the uterine wall for the implantation of a fertilized ovum. If the ovum is not fertilized, the lining wall is broken down the discharge from the body. This is called menstruation. Normally the menstrual cycle starts at the age of 10-14 years and stops at the age of 45-50 when menopause is reached.

Question 4.
List changes in the body that takes place at puberty.
Puberty. Puberty is period between the age of 11 to 19 years. Following changes take place at the onset of puberty.

1. Changes taking place at puberty in boys.

1. Height increase suddenly. The bones of legs and arms become long and make a boy tall.
2. Boy’s shoulders become broader and chest also become wider.
3. Muscles of the body grow more prominently.
4. The voice becomes hoarse. Adam’s apple, a protruding part of throat is seen. They have a deep voice.
5. They get acne and pimples on the face at this time due to the increased activities
of sweat and subaceous glands.
6. Male sex organs like testes and penis develop completely.
7. Boys develop hair on their chest, under the arms and on the pubic region.

2. Changes taking place at puberty in girls.

1. Height also increases in girls but comparatively less.
2. The region below the waist becomes wider.
3. In girls the larynx is hardly visible from the outside. Girls have a high pitched voice.
4. Like boys girls also get pimples on the face.
5. The ovaries enlarge and eggs begin to mature.
6. Breasts begin to develop.
7. Hair grow under the arms and also on the pubic region.

Question 5.
Prepare a table having two columns depicting names of endocrine glands and hormones secreted by them.
The table given ahead indicates the endocrine glands and their hormones:

 Endocrine gland Hormones (i) Pituitary gland (i) Growth Hormones (ii) Thyroid (ii) Thyroxine (iii) Adrenal (iii) Adrenalin (iv) Pancreas (iv) Insulin (v) Testis (v) Androgen (Testosterone) (vi) Ovaries (vi) Estrogen

Question 6.
What are sex hormones ? Why are they named so ? State their function.
Sex hormones.
There are the hormones secreted by testes in males and ovaries in females. They are named so because they are secreted by male and female sexes separately.

Male Sex hormone (Testosterone).
It is secreted by testes. It causes changes in boys like growth of facial hair. It also stimulates spermatogenesis.

Female sex hormone (Estrogen).
It is secreted by ovaries. It controls the development of secondary sexual characters in females, appearance of mammary glands etc. It maintains pregnancy.

Question 7.
Choose the correct option.
(i) proper diet develops their brains.
(ii) proper diet is needed for the rapid growth taking place in their body.
(iii) adolescents feel hungry all the time.
(iv) taste buds are well developed in teenagers.
(ii) proper diet is needed for the rapid growth taking place in their body.

[b] Reproductive age in women starts when their
(i) menstruation starts.
(ii) breasts start developing.
(iii) body weight increases.
(iv) height increases.
(i) menstruation starts.

[c] The right meal for adolescents consists of
(i) Chips, noodles, coke.
(ii) Chapati, dal, vegetables.
(iii) Rice, noodles and burger.
(iv) Vegetable cutlets, chips and lemon drink.
(ii) chapati, dal, vegetables.

Question 8.
Write notes on:
(b) Secondary sexual characters.
(c) Sex determination in the unborn baby.

At puberty boys develop larger voice box or larynx. This box in boys is seen as a protruding part of the throat called Adam’s apple.

(b) Secondary sexual characters.
We know testis and ovaries are the reproductive organs. They produce the gametes i.e. sperms and ova. In girls, breasts begin to develop at puberty and boys begin to grow facial hair, i.e. moustaches and beard. As these features help to distinguish the male from the female they are called secondary sexual characters. Boys also develop hair on their chest. In both boys and girls hairs grow under the arms and in the region above the thighs or the pubic region.

(c) Sex determination in the unborn baby.
Determination of the sex of child. Sex chromosomes determine sex in human beings. In males, there are 44 + XY chromosomes, whereas, in females there are 44 + XX chromosomes. Here X and Y chromosomes determine sex in human beings.

Two types of gametes are formed in male, one type is having 50% X-chromosome, whereas, other type is having Y-chromosome. In female, gametes are of one type and contain X-chromosome.

Thus females are homogametic. If male gamete having Y-chromosome undergoes fusion with female gamete having X-chromosome the zygote will have XY chromosome and this gives rise to male child.

If male gamete having X-chromosome undergoes fusion with female gamete having X-chromosome, the zygote will be having XX-chromosome and this gives rise to female child.

Question 9.
Word game : Use the clues to work out the words.
Across
3. Protruding voice box in boys
4. Glands without ducts
7. Endocrine gland attached to brain
8. Secretion of endocrine glands
9. Pancreatic hormone
10. Female hormone

Down
1. Male hormone
2. Secretes thyroxine
3. Another term for teenage
5. Hormone reaches here through blood stream
6. Voice box
7. Terms for changes at adolescence

Question 10.
The table below shows the data on likely heights of boys and girls as they grow in age. Draw graphs showing height and age for both boys and girls on the same graph paper. What conclusions can be drawn from these graphs?

The above graph shows that the increase in the growth in heights of boys and girls is same. The increase in growth is less in girls upto first eight years and after that it remains the same upto twenty years.

PSEB Solutions for Class 8 Science Reaching the Age of Adolescence Important Questions and Answers

Multiple Choice Questions

Question 1.
Adolescent period normally start from …………………. of age.
(a) 9
(b) 11
(c) 13
(d) 15.
(b) 11.

Question 2.
Adolescence period ends in the ……………….. year of age.
(a) 19
(b) 22
(c) 25
(d) 27.
(a) 19.

Question 3.
Menstrual period of human female is of how many days ?
(a) 20 days
(b) 22 days
(c) 18 days
(d) 28 days.
(d) 28 days.

Question 4.
The stoppage of menstrual cycle is called:
(a) Menopause
(b) Menstruation
(c) Metaphorsis
(d) None of these.
(a) Menopause.

Question 5.
Female sex harmone is called:
(a) Estrogen
(6) Testosterone
(d) Thyroxin.
(a) Estrogen.

Question 6.
The male sex harmon is:
(a) Estrogen
(c) Testosterone
(d) Thyroxin.
(c) Testosterone.

Question 1.
Name two endocrine glands in humans.

1. Pituitary
2. Thyroid.

Question 2.
Which of the endocrine gland secretes growth hormone ?
Growth hormone is secreted by pituitary gland.

Question 3.
What are female sex cells called ?
Ova.

Question 4.
When do human stop growing ?
Human stops growing after about 20-25 years of age.

Question 5.
What is the main element of thyroxine hormone ?
Iodine.

Question 6.
In which part adrenaline is produced ?

Question 7.
Name the male and female sex hormones.
Testosterone, Estrogen.

Question 8.
Name the following:
(i) The types of glands that secrete hormones.
(ii) The other name of hormones.
(iii) The gland which is called ‘Master gland’.
(iv) The hormone secreted by thyroid gland.
(v) The disease caused by the deficiency of iodine.
(vi) The hormones that control blood glucose level.
(vii) The gland which produces the so called ‘emergency hormone’.
(i) Endocrine glands or ductless glands
(ii) Chemical coordinators
(iii) Pituitary gland
(iv) Thyroxine
(v) Goitre
(vi) Insulin and glucagon

Question 9.
Define sex chromosomes.
Sex chromosomes.
The chromosomes associated with sex determination are called sex chromosomes. XX in female and XY chromosomes in male are called sex chromosomes.

Question 10.
How many chromosomes are found in human cells ?
46 (44 autosomes and a pair of sex chromosomes).

Question 11.
When do adolescence begins and ends ?
Adolescence begins at the age of 11 years and lasts upto the 18 or 19 years of age.

Question 12.
The glands which pour their secretions directly into the blood stream is called ……………. ?
Endocrine glands.

Question 13.
What is target site ?
Target Site. Target site is a body part where the hormones act.

Question 14.
What is the period of reproductive phase in females ?
The reproductive phase begins at puberty (10-12 years) and lasts till the age of 45-50 years.

Question 15.
Define menarch.
Menarch. The first menstrual flow in females begins at puberty which is called menarch.

Question 16.
Define Menopause.
Menopause. Stoppage of menstruation is called menopause.

Question 17.
What are the sex chromosomes in males and females ?
Females have two X-chromosomes (XX), Males have one X and one Y-chromosome (XY).

Question 18.
To which body part pituitary gland is attached ?
Pituitary gland is attached to brain.

Question 19.
Name the hormones which control metamorphosis in insects and frog.
In insects-Insect hormone In frog-Thyroxine.

Question 20.
Expand AIDS.
AIDS. Acquired Immuno Deficiency Syndrome.

Question 21.
What is the legal age of marriage in India ?
The legal minimum age for marriage is 18 years for girls and 21 years for boys.

Question 1.
How does hormone affect a girl’s body between the age of 10-15 years ?
Hormones affect girl’s body by making the breast to become bigger and hips becoming more rounded.

Question 2.
How does hormone affect a boy’s body between the age of 11-16 years ?
In boy’s body, the following changes are caused by hormones:

1. his voice becomes hoarse (deeper)
2. hairs start to grow on his face and body.
3. his body muscles develop.
4. his testis start producing sperms.

Question 3.
Write short notes on :
(i) Menstruation
(ii) Menopause.
(i) Menstruation.
Destruction of the mucous membrane of foetus and consequent bleeding which occur periodically in human and other mammals.

(ii) Menopause.
Stoppage of menstrual flow and other events is called menopause. It occurs between 45 to 55 years.

Question 4.
Explain sexual cycle in human female.
Sexual cycle.
The rhythmic changes in the uterus which occur about every 28 days throughout the reproductive cycle of woman except the pregnancy period is called menstrual cycle. The female sex hormones initiate the thickening of the uterine wall for the implantation of a fertilized ovum.

If the ovum is not fertilized, the lining wall is broken down and discharged from the body. This is called menstruation. Normally the menstrual cycle starts at the age of 10-14 years and stops at the age of 45-50 when menopause is reached.

If the ovum is fertilized by sperm, the zygote develops in the wall of uterus and developing embryo called foetus is nourished by placenta. During the period, ovulation or ‘menstruation does not occur. However these activities are restored after child birth.

Question 5.
What is meant by reproductive health ?
Reproductive health.
Reproductive organs are important organs of the body. Proper knowledge and hygiene of these organs is important otherwise persons may get some sexually transmitted diseases such as AIDS, syphilis and gonorrhoea.

Question 6.
Write modes of transmission of AIDS.
Modes of transmission of AIDS. It is transmitted during transfusion of infected blood, use of contaminated needles, artificial insemination and several intercourse with an infected partner without a condom.

Question 7.
Differentiate between menarch and menopause.
Differences between Menarch and Menopause

 Menarch Menopause 1. Commencement of menstruation at puberty is called menarch. 1. Stoppage of menstrual flow and other events is called menopause. 2. It starts at the age of 11 to 12 years. 2. It stops around the age of 50 years.

Question 8.
Write whether True (T) or False (F):
(i) Fertilization is process of fusion of sperm and ovum.
True

(ii) Duration of menstrual cycle in human female is 20 days.
False

(iii) Onset of menstruation is termed as menopause.
False

(iv) In human beings, males attain puberty little later than females.
True

Question 9.
Why the endocrine glands are called ductless glands ?
The transport of hormones from one place to another takes place through body fluids, rather than through the ducts. Therefore, the endocrine glands are also called ductless glands.

Question 10.
Which gland secretion reduces pituitary secretion ?
Increased secretion of thyroxin from the thyroid gland reduces the production of hormones by the pituitary gland.

Question 11.
Adrenalin secretion increases during a frightening situation. What is the response ?
Frightening experience (scene) is the stimulus which causes the increase of adrenalin secretion. Therefore, increased adrenalin secretion acts as response to the stimulus.

Question 12.
Draw a diagram showing various endocrine glands.

Question 13.
List some of the functions of pituitary gland.
Functions of pituitary gland.

1. Regulates growth.
3. Can produce changes in the skin colour of many amphibians and fishes.
4. Influences migration and nest building in birds.

Question 14.
Why should an adolescent eat right kind of food ?
Adolescents are in growing years. It is very important to eat right kind of food. It helps in the better nourishment of growing bones, muscles and other parts of body.

Question 15.
Why do adolescents become independent than before ?
Adolescents are more independent than before and are also self conscious. It is a period of change in a person’s way of thinking. Intellectual development takes place and they tend to spend more time in thinking. In fact, it is often the time in one’s life when the brain has the greatest capacity for learning. Sometimes, however, an adolescent may feel insecure while trying to adjust to the changes in the body and mind.

Question 16.
How will you explain that sex hormones are under the control of pituitary glands ?
The sex hormones are controlled by pituitary gland. The gland secretes many hormones, one of which is FSH or Follicle Stimulating Hormone. It makes ova and sperms mature in the ovaries and testis respectively. It can be shown as follows:
Hormones from pituitary stimulates gonads to release Testosterone (in male) and Estrogen (in female)
Released in the blood stream and reach parts of the body (Target site)
Stimulate changes in the body and onset of puberty.

Question 17.
Adolescent should say ‘No’ to the drugs. Why ?
Adolescence is a period of much activity in the body and mind. So, do not feel confused or insecure. If anybody suggests that you will get relief if you take some drugs, just say ‘No’ unless prescribed by doctor. We know that drugs are addictive, if you take them once, you feel like taking them again and again. They harm the , body in the long run. They ruin health and happiness.

Question 18.
One comes across many myths and taboos. We should discard them. These myths are as follows-

1. A girl becomes pregnant if she looks at boys during menstruation,
2. A drop of semen lost means loss of 10 drops of blood which will make the boy weak.
3. The mother is responsible for the sex of her child.
4. A girl should not be allowed to work in the kitchen during menstruation.

Question 19.
What changes occur in voice at the time of puberty ?
At puberty, the boys develop larger voice box and it can be seen as a protruding part. The voice of boys becomes hoarse and cracked due to increase in larynx. Such kind of difference is not visible in the voice box or larynx of girls. The girls have a high pitched and sweet voice due to smallness of larynx.

Question 20.
Write the main characteristics of hormones.
Main characteristics of hormones are following:

1. Hormones are secreted by endocrine glands. They have specific functions.
2. Hormones are required in very little quantity,
3. These effect only specific organs.

Question 21.
Why is pituitary gland called master gland ?
This gland is located in the lower portion of the brain. The hormone secreted . by it controls the growth of bones and tissues. This gland secretes a hormone which controls the function of other glands, therefore, it is called master gland.

Question 22.
What is reason behind this fact that boys and girls should not be married in young age ?
In young age, the body of adolescents, especially reproductive organs, are not ready for motherhood. If marriage takes place in such a situation, then such couples may face many health problems which can cause stress. In our country, the legal age for marriage is 18 years for girls and 21 years for boys when adolescents are allowed to get married. The adolescents below this age are not allowed to marry under the law of marriage and it is legally wrong doing so.

Question 23.
Why there is great possibility of disease HIV-AIDS in adolescents ?
Many adolescents start taking drugs to make themselves stress free. By taking drugs from HIV contaminated needle of injection, this dangerous virus spreads in other adolesqents. The other reason of spreading this virus is unsafe sexual relationship. In many cases, this virus may enter in infants through the milk of mother.
So,it is very necessary for adolescents to remain aware to save their precious life from HIV.

Question 24.
List any two changes in the body that take place at puberty.
Changes taking place in boys at puberty.

1. Height increase suddenly. The bones of legs and arms become long and make a boy tall.
2. Boy’s shoulders become broader and chest also become wider.

Changes taking place at puberty in girls.

1. Height also increases in girls but comparatively less.
2. The region below the waist becomes wider.

Question 1.
Give a chart showing the average rate of growth in height with age.

Calculation for full height (cm)
Present height (cm)
= $$\frac{\text { Present height }(\mathrm{cm})}{\% \text { of full height at this age }}$$ × 100
(as given in the chart)
For example : A boy is 8 years old and 108 cm tall. At the end of the growth period he is likely to be
$$\frac{108}{72}$$ × 100 cm = 150 cm tall.

Question 2.
Describe the various conditions or factors needed for keeping the body healthy during adolescence.
During adolescence following conditions are essential for healthy body—
1. Nutritional needs.
Adolescence is a stage of rapid growth and development, hence the diet for an adolescent has to be carefully planned. A balanced diet means that the meals should include proteins, carbohydrates, fats, vitamins and minerals in the requisite proportion. Our Indian meal of roti/rice, dal (pulses) and vegetables, milk, fruits is a balanced meal.

Chips and packed or tinned snacks, though very tasty should never replace regular meals as they do not have adequate nutritional value.

2. Personal hygiene.
Having bath at least once everyday is more necessary for teenagers because the increased activity of sweat glands sometimes makes the body smelly. All parts of the body should be washed and cleaned everyday. If cleanliness is not maintained, there are chances of catching bacterial infection. Girls should keep track of their menstrual cycle and be prepared for the onset of menstruation. Undergarments should be changed everyday. Cotton undergarments should be preferred.

Reaching the Age of Adolescence PSEB 8th Class Science Notes

• It is after growing up to a certain age that human beings and other animals become capable of reproduction.
• On crossing the age of 10 or 11 in human beings there is sudden spurt in growth.
• Growth is a natural process.
• The period of life when the body undergoes changes, leading to reproduction maturity is called adolescence.
• Adolescence begins at the age of 11 and lasts upto 18 or 19 years of age.
• Adolescents are also called teenagers.
• The human body undergoes severe changes during adolescence which marks the onset of puberty.
• The most conspicuous change during puberty is height.
• The rate of growth in height varies in different individuals.
• All the body parts do not grow at the same rate.
• Height also depends on the genes inherited from parents.
• At puberty voice box begins to grow. Generally girls have a high pitched voice, whereas the voice in boys is deep.
• During puberty the secretion of sweat glands and subaceous glands also increases.
• Endocrine glands release hormones directly into the blood stream.
• Adolescence is also a period of change in a person’s way of thinking.
• The appearance of secondary sexual characters help in distinguishing males from females. ,
• Changes occurring at adolescence are controlled by hormones which are the chemical substances secreted by endocrine glands.
• Hormones are secreted by endocrine or ductless glands. The endocrine glands are pituitary, adrenal, thyroid and gonads. Pancreas is an exocrine as well as an endocrine gland.
• Pheromones are the hormones present in the insects.
• An endocrine gland does not have duct and is, therefore, also called ductless gland. .
• A ductless or endocrine gland pours its secretion into circulatory system of the body for sending to the target cells.
• Secretions of endocrine glands are called hormones.
• Testes or male gonads are mixed organs which produce sperms as well as male sex hormones or androgens (e.g., testosterone, androsterone).
• Ovary secretes estrogen and progesterone hormones.
• The cyclic changes that occur every 28 days .(lunar month) in the reproductive tract of human females from the period of puberty to the age of menopause is called menstrual cycle.
• At the age of 45-50 women stop menstruation. It is called menopause.
• There are 23 pairs of chromosomes in human.
• There are 22 pairs of autosomes and 1 pair of sex chromosomes in human beings.
• The change from larva to adult is called metamorphosis. These changes are also controlled by hormones.
• The physical and mental well being of an individual is regarded as an . individual’s health.
• Diet for an adolescent has to be carefully planned as it is a stage of rapid growth and development.
• The personal hygiene is more necessary for teenagers because the increased activity of sweat glands make body smelly.
• All adolescents should take walks, do exercise and play another games.
• Adolescence: Children between the ages of 10 or 11 years to 18 or 19 years are called adolescents. This period of age is called adolescence.
• Puberty: It is a period (11 to 18 years) when the reproductive organs start functioning.
• Voice Box: It is box consisting of cartilages present in the throat of human beings causing voice.
• Adam’s Apple: In boys the growing voice box is seen as a protruding part of the throat called Adam’s apple.
• Secondary Sexual Characters: In boys and girls some characters are present which help to distinguish them.
These are called secondary sexual characters.
• Endocrine Glands: The ductless glands present in animals which secrete hormone and pour them directly into the blood stream are called endocrine glands.
• Hormones: These are the chemical secretions secreted by endocrine glands to control the activities of human bodies.
• Target Site: It is particular body part where hormones released by the endocrine glands through blood stream reach.
• Pituitary Gland: It is a master gland present on the brain.
• Testosterone: It is a male hormone secreted by the testes at the onset of puberty.
• Estrogen: It is a female hormone released by the ovaries at the onset of puberty which makes the breasts develop.
• Sex Chromosomes: Human beings have 23 pairs of chromosomes. One pair out of them (23rd pair) is called sex chromosome.
• Thyroxine: It is a hormone secreted by thyroid gland situated in neck.
• Insulin: It is a hormone secreted by the pancreas which controls sugar level in the blood.
• Adrenalin: It is a hormone secreted by adrenal gland which maintains the salt balance in the blood.
• Balanced Diet: A diet which contains the various components of food (carbohydrates, fats, proteins, minerals, vitamins, water) in the right proportion.
• Health: The physical and mental well being of an individual is regarded as individual’s health.

Punjab State Board PSEB 8th Class Science Book Solutions Chapter 10 Reaching the Age of Adolescence Textbook Exercise Questions and Answers.