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

Rajasthan Board RBSE Solutions for Class 8 Science Chapter 10 Reaching the Age of Adolescence Textbook Exercise Questions and Answers.

RBSE Class 8 Science Solutions Chapter 10 Reaching the Age of Adolescence

RBSE Class 8 Science Reaching the Age of Adolescence InText Questions and Answers

Page 113

Question 1. 
I wonder how long this period marked by changes in the body will last!
Answer:
The period of such changes in the body begins around the age of 11 and lasts upto 18 or 19 years of age.

Question 2. 
It is a strange period of life when you are neither a child nor an adult. I wonder whether the period between childhood and adulthood has a special name!
Answer:
The period between childhood and adulthood is called adolescence.

Page 117

Question 3. 
Both Boojho and Paheli wish to know what initiates changes at puberty?
Answer:
Different hormones initiate the changes at puberty. 

Question 4. 
Paheli and Boojho have now understood that puberty marks the beginning of the reproductive period when one becomes capable of reproduction. But they want to know if reproductive life, once begun, is it continued, or it ends after some time.
Answer:
Reproductive life is not continued. In females it generally lasts till the age of approximately 40 to 50 years. This period lasts for a much longer time in males than in females.

Page 118

Question 5. 
Paheli says that the reproductive life of a woman lasts from menarche to menopause. Is she right?
Answer:
Yes, she, is right.

Question 6. 
I heard my mother and my aunt talking about my cousin who is going to have a baby. They were discussing whether she would give birth to a boy or a girl. I wonder what makes the fertilized egg develop either into a boy or a girl!
Answer:
Inside the fertilized egg or zygote is the instruction for determining the sex of a baby. In this process sex chromosome helps. We know that all human beings have 23 pairs ofchromosomes in the nuclei of their cells. Two chromosomes (1 pair) out of these are the sex chromosomes, named X and Y.

A female has two X chromosomes, while a male has one X and one Y chromosome. The gametes (egg and sperm) have only one set of chromosomes. The unfertilized egg always has one X chromosome. But sperms are of two kinds. One kind has a X chromosome, and the other kind has a Y chromosome.

When a sperm containing X chromosome fertilises the egg, the zygote would have two X chromosomes and develop into a female child. If the sperm contributes a Y chromosome to the egg (ovum) at fertilisation, the zygote would develop into a male child.

Page 120

Question 7. 
Are there hormones in other animals also? Have they any role to play in reproduction?
Answer:
Yes, other animals also secrete hormones. They play role in reproduction.

Question 8. 
If people do not have enough iodine in their diet, will they get goitre caused by lack of thyroxine?
Answer:
Thyroid gland requires the presence of iodine for production of thyroxine. If people do not have enough iodine in the diet, sufficient thyroxine will not be formed. The person will suffer from 'goitre' disease.

RBSE Class 8 Science Reaching the Age of Adolescence Textbook Questions and Answers     

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

Question 2. 
Define adolescence.
Answer:
The period of life, when the body undergoes changes, leading to reproduction maturity, is called adolescence. Adolescence begins around the age of 11 and lasts upto 18 or 19 years of age.

Question 3. 
What is menstruation? Explain.
Answer:
If fertilisation does not occur, the released egg, and the thickened lining of the uterus along with its blood vessels are shed off. This causes bleeding in women which is called menstruation. Menstruation occurs once in about 28 to 30 days.

The first menstrual flow begins at puberty and is termed menarche. At 45 to 50 years of age, the menstrual cycle stops. Stoppage of menstruation is termed menopause.

Question 4. 
List changes in the body that take place at puberty.
Answer:
The body changes at the time of puberty:
1. Increase in height:
At this time the long bones elongate and make a person tall. Approximately about 18 year of age, both girls and boys reach to their maximum height, the height depends on the genes inherited from parents.

2. Change in body shape:
In boys shoulders become broader and in girls, the region below the waist becomes wider. In boys, the muscles of the body grow more prominently than in the girls.

3. Changes in voice:
Boys develop large voicebox and sometimes the voice cracks. In girls voicebox is comparatively of small size and has a high pitch.

4. Increased activity of sweat and sebaceous glands:
During puberty the secretion of sweat glands and sebaceous glands increases. Many young people get acne and pimples on their faces at this time.

5. Development of sex organs:
Male reproductive organs develop. The testes begin to produce sperms. In girls, the ovaries enlarge and eggs begin to mature. Also ovaries start releasing mature eggs.

6. Reaching mental, intellectual and emotional maturity:
Adolescents are more independent than before and are also self conscious. At this time they possess greatest capacity of learning. Sometimes, due to changes adolescent mgny feel insecure.

Question 5. 
Prepare a Table having two coloumns depicting names of endocrine glands and hormones secreted by them.
Answer:

Endocrine glands	Hormone
1. Pituitary	Growth hormone
2. Thyroid	Thyroxine hormone
3. Adrenal	Adrenalin
4. Pancreas	Insulin
5. Testes	Male hormone (Testosterone)
6. Ovary	Estrogen.

Question 6. 
What are sex hormones? Why are they named so? State their function.
Answer:
Sex hormone:
Testes in male and ovary in female secret hormones which are called sex hormones. The separate name is given to them because they are different in male and female sex. 

Male sex hormones (Testosterone):

1. They are secreted by testes.
2. By them there is growth of facial hair in boys.
3. They develop the capacity to produce sperms. 

Female sex hormones (Estrogen):

1. They are secreted by ovaries.
2. They control the secondary sexual characters in female like growth of breasts etc.
3. They are helpful in pregnancy.

Question 7. 
Choose the correct option:
(a) Adolescents should be careful about what they eat, because
(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.

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

(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. 
Answer:
(a)  (ii) proper diet in needed for the rapid growth taking place in their body.
(b) (i) menstruation starts.
(c) (ii) chapati, dal, vegetables.

Question 8. 
Write notes on
(a) Adam’s apple.
(b) Secondary sexual characters.
(c) Sex determination in the unborn baby. 
Answer:
(a) Adam's apple:
At puberty, the voice box or the larynx begins to grow. Boys develop larger voice boxes. The growing voice box in boys can be seen as a protruding part of the throat called Adam's apple.

(b) Secondary sexual characters:
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, hair grows under the arms and in the region above the thighs or the pubic region.

(c) Sex determination in the unborn baby:
All human beings have 23 pairs of chromosomes in the nuclei of their cells. Two chromosomes out of these are the sex chromosomes, named X and Y. A female has two X chromosomes, while a male has one X and one Y chromosome.

The gametes (egg and sperm) have only one set of chromosomes. The unfertilised egg always has one X chromosome. But sperms are of two kinds. One kind has an X chromosome, and the other kind has a Y chromosome.

When a sperm containing X chromosome fertilises the egg, the zygote would have two X chromosomes and develop into a female child. If the sperm contributes a Y chromosome to the egg (ovum) at fertlilisation, the zygote would develop into a male 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.Term for changes at adolescence.

Answer:

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?

Age (Years)	Height (cm.)
	Boys	Girls
0	53	53
4	96	92
8	114	110
12	129	133
16	150	150
20	173	165

Answer:
Conclusion derives from above graph that at the time of birth both girls and boys having the same length, after 4-8 year the height of boys grows faster than girls and after the gap of 8-12 year the height of girls increases faster than boys. As they reach 16 year of age both reach to same height but in 16 to 20 years of age the height of boys is more than the girls.