Reaching The Age Of Adolescence - Class 8 Biology - Extra Questions

Discuss the various habits that adolescents should acquire to have a proper physical health.

Proper physical health in adolescents is a need.
  • A balance diet containing the right amounts of proteins, carbohydrates, fats, vitamins and minerals.
  • Fast food which is tasty but does not have adequate nutrition, such as chips or aerated drinking, should not be used as substitute for meals.
  • Personal hygiene due to increased activity of sweat and sebaceous glands, proper personal hygiene is very important for adolescents, otherwise body odour and bacterial infection may result. Girls should be especially careful about hygiene during menstruation.
  • Physical exercise like walking, jogging, aerobics, outdoor games etc are good for the growing adolescent body.


Once puberty is reached in girls, ovaries begin to produce the _________.

Once puberty is reached in girls, ovaries begin to produce the female hormone or estrogen. Estrogen is responsible for the development of breasts.


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

During puberty, there is a sudden spurge in height of both boys and girls. From the graph, we can see that during the age of 4-8 years, girls have less height as compared to boys. However, as soon as girls reach the start of adolescent phase, i.e. 12- 13 years, their height shows a sudden increase and becomes more than boys. In later years, the rate of increase in height, increases for boys. Generally, after an age of 20 the growth stabilizes in both sexes. 

491420_462853_ans_7bd6979f2b3f446e85a28a22550b11d2.png


Define adolescence.

Adolescence is the period of life, when the body undergoes changes, leading to reproductive maturity, is called adolescence.



Write notes.
(a) Adam's apple.
(b) Secondary sexual characters.
(c) Sex determination in the unborn baby.

(a) Adam's apple: The protruding part of the throat formed due to the enlargement of larynx is called as Adam’s apple. This enlargement of larynx or voice box occurs during puberty. Voice becomes hoarse.

(b) Secondary sexual characters:  Characters which usually appear during the phase of puberty are called as secondary sexual characters. These are the features that help in distinguishing the male and the female body from each other. 
Characters seen in male: Hoarseness of voice, appearance of beard, broadness of chest, growth of hair in genital areas.
Characters seen in female: Start of menstrual cycle, growth of breast, growth of hair in the genital areas.

(c) Sex determination in an unborn baby: Sex of a unborn baby depends upon the pair of sex chromosomes that are present in the cells of the baby. 
X and Y chromosomes are the sex chromosomes in humans. Ovum always contain X chromosome, male sperm may carry either X chromosome or Y chromosome. Male genetic make-up is 44 autosomes + XY chromosome and female genetic make-up is 44 autosomes  + XX chromosomes.


"The sex of a newborn child is a matter of chance and none of the parents may be considered responsible for it." Justify this statement with the help of  chart showing determination of sex of a newborn.

The hemizygous males produce two kinds of gametes, 1/2 gametes with X- and 1/2 with Y-chromosome (22 A + X and 22 A + Y). Fertilization of egg (22 + X) with sperm carrying 22+X chromosomes results in female child (44A + XX). Fertilization of egg (22 + X) with a sperm carrying 22+Y chromosomes results in a male child (44A + XY). 

 44 + XX (Female)
 44 + XY (male)		  22+X   22+X 
  22+X 44 + XX 
(Girl)		44 + XX 
(Girl)
  22+Y44 + XY
(boy)
44 + XY
(boy)


Women are often blamed for producing female children. Consequently, they are ill-treated and ostracized. How will you address this issue scientifically if you were to conduct an awareness programme to highlight the values involved?

The sex of the child is determined by the type of gamete he receives from the father as father contains two different types of gametes X and Y while mother contains only one type of gamete i.e. X. When male X combines with female X, a male child is borne and when male Y combines with female X, a female child is born. Thus females are never responsible for determination of the sex of a child. So, women should not be ill-treated for giving birth to a girl child, as both males and females are equally important for the balance of nature and continuity of our species. 


What happens to the wall of the uterus during menstruation?

In females, one ovum matures and is released by one of the ovaries once every 28 - 30 days. During this period, the wall of the uterus becomes thick so as to receive the fertilized egg. The fertilized egg embeds itself into the uterine lining. This event results in pregnancy. If in case, fertilization 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 thus, called menstruation.


In frogs, thyroid secretion stimulated the metamorphosis from tadpole to adult frog. Is it true or false?

$$\textbf{Correct answer True}$$

$$\textbf{Solution:}$$

$$\bullet$$Tadpole metamorphosis takes anywhere from one to two weeks to several years in amphibians, depending on the species. 
$$\bullet$$Physiological and morphological changes are involved in the process. 
$$\bullet$$Thyroxine, a hormone generated by the thyroid gland, is crucial for the metamorphosis of a frog.



What is the importance of personal hygiene during the age of adolescence?

  • Personal level hygiene mainly involves cleanliness, adequate rest and sleep, physical exercise etc. 
  • Adolescence is the onset of puberty. During this period, many changes occur like the sweat glands are more active. This could cause more sweating. In addition to this, the hair growth in public regions and armpit make it even worse.
  • Hence, one must maintain cleanliness by proper hand washing, regular bathing, washing, and ironing of clothes. 
  • Girls have to keep themselves clean particularly during menstruation. 
  • Regular walk, outdoor games, and workouts are important for adolescents. These help them remain physically fit and healthy.


Do both girls and boys grow on same rate? Why?

No, the boys and girls grow at different rates. In girls, the puberty occurs earlier than boys. That is why during the early adolescent years, the girls are taller than boys. However, the growth spurt in girls is shorter than that of boys so right after the start of the menstrual cycle, the growth on girls gets slower than the growth in boys. The basal metabolic rate of boys and girls differ that acoounts of dfference in the growth rate.



What causes pimples to appear in adolescents?

At the adolescence stage, the activity of the sebaceous glands increases in the young boys and girls due to the hormonal influence. This is the time of puberty. It is regarded as one of the many secondary sexual characters. The increased secretion of sebum causes appearance of acne or pimples in adolescents.


What are sex hormones? Why are they named so? State their functions.

Hormones which are secreted by testis in males and ovaries in females are called Sex Hormones. In males, it is testosterone and in females it is estrogen. They are named so because these hormones are responsible for the male and female secondary sexual characteristics. 
In females, the primary function of estrogen is the development of secondary sexual characteristics such as the development of breast, maturation of endometrium and regulation of the menstrual cycle. Whereas in males, it is testosterone that plays a key role in the development of male reproductive tissues such as prostate and testes and also promotes secondary sexual characteristics such as increased muscles and bone mass and growth of body hair.


Discuss about menarche and menopause.

$$\large\textbf{Solution}$$

$$\textbf{Menarche}$$
$$\bullet$$ Menarche is the period of onset of puberty in females which is characterized by menstruation in them.
$$\bullet$$ It usually occurs between the ages of 10-14 years.

$$\textbf{Menopause}$$
$$\bullet$$ Menopause is the period when ovulation and menstrual cycle stop in females and fertility ends.
$$\bullet$$ Menopause generally occurs between the age of 50-52 years.


How many pairs of chromosomes are present in human beings? 
Out of these, how many are sex chromosomes? How many types of sex chromosomes are found in human beings? 
"The sex of a newborn child is a matter of chance and none of the parents may be considered responsible for it" Draw a flowchart showing the determination of the sex of a newborn to justify this statement. 

$$\textbf{Solution:}$$
$$\textbf{Part 1:}$$
$$\bullet$$ There are 23 pairs of chromosomes in cells of human beings.

$$\textbf{Part 2:}$$
$$\bullet$$ Out of 23 pairs, 1 pair consists of sex chromosomes and 22 pairs are autosomes.
$$\bullet$$ There are two types of sex chromosomes X and Y chromosomes.

$$\textbf{Part 3:}$$
$$\bullet$$ In humans, sex is determined on the basis of presence of sex chromosomes, X and Y chromosome.
$$\bullet$$ Male has X and Y chromosomes (XY), while the female has two X chromosomes (XX).
$$\bullet$$ The sperm has an X chromosome or Y chromosome while an egg has only X chromosome.
$$\bullet$$ After fertilization, if a zygote has XY chromosomes then it develops into male child whereas, if a zygote has XX chromosome then it develops into a female child.



A new born child has an XY pair of chromosomes. Will it be a baby boy or a baby girl?

The new born having an XY pair of chromosomes will be a baby boy.


Give a suitable word for each of the following statements.
Chemicals which control changes at adolescence stage. 

Hormones are the chemicals that control changes at adolescent stage.


What do you think would happen if the thyroid gland of a tadpole is removed?

  • In a frog thyroxine, the hormone is produced by thyroid gland. 
  • Thyroxine production requires the presence of iodine in water. If the water in which the tadpoles are growing does not contain sufficient iodine, the tadpoles cannot become adults.
  • So, if the thyroid gland is removed tadpole cannot become adult.


Which of the line represents the height of boys?

The red line is representing the height of boys. 


John and Radha were classmates since childhood. When Radha became eleven years old, she developed a little swelling on her neck. She visited the doctor who started medication for her. After a few years, John also developed a slight protrusion on his throat. He got worried and went to the doctor. But, the doctor assured him that it was a normal feature in boys while they are growing up. Can you think of any reasons for the difference in diagnoses?

Radha's neck may be swollen  because of Goitre. When the thyroid gland is unable to make sufficient quantity of thyroxin, the thyroid glands swell, which results in goitre.
Neck of John developed a protrusion because of Adam's apple, which results in the growth of voice box in adolescent boys. 


Complete the following sentences.
The sex hormones, _____ and estrogen are responsible for the development of _______ characters. 

The sex hormones Testosterone and estrogen are responsible for the development of secondary sexual  characters. 


What is the difference between the pattern of increase in the height of boys and girls?

At the beginning of puberty, boys grow slower in height than the girls, and both reach their maximum height by the age of 18 years. 


Which line represents the height of girls

The blue line represents the height of girls.


Answer the following question is short.

Which precautions will you follow to maintain the reproductive health?

Precautions which should be taken in order to maintain good reproductive health are: 
• Eat a balanced and nutritious diet 
• Maintain personal hygiene 
• Take adequate physical exercise 
• Avoid taking any drugs 


How physical hygiene can be maintained during adolescence?

Physical hygiene is also known as personal hygiene. It plays a crucial role in maintaining health during adolescence. The adolescents should follow the below-mentioned activities to promote their health:
1. Proper and safe food: Adolescence is the stage of rapid growth and development. Hence, a teenager should take proper care of their diet. They should follow a balanced diet. They should consume freshly prepared food and avoid stale food and junk food. They should take milk, fruits, and fresh vegetables.
2. Proper lifestyle: Regular exercise and sleep are necessary for maintaining good health. A teenager should avoid long hours of continuous table work, television watching. A teenager should not consume alcohol, drugs, or smoke.
3. Cleanliness: Teenagers should take baths regularly. They should always change and wear washed clothes especially undergarments. Regular toilet habits should be adopted for maintaining good health. Girls should take special care of cleanliness during the time of the menstrual period.
4. Physical Exercise: In order to keep the body fit and healthy, teenagers should walk, exercise, and play outdoor games regularly in the fresh air. Playing Outdoor games reduces the stress and strain of adolescence.


Is this pattern true for each individual? 

No, the rate of growth in height varies among individuals. Some may increase in height suddenly at puberty and then slow down, while others may grow gradually. It completes depends on their genetic make up, and also on nutrition and exercise.


What are the secondary sexual characters in male and female?

Secondary sexual characters are those characters that are governed by the hormones released at the time of puberty, and usually is around two years earlier in females than man.

The secondary sexual characteristics in males are :
Hair growth on the face in the form of beard and moustache
The growth of his testicles
Heavier musculature
Adam's apple development
Larynx becomes larger results in a deeper voice

Some of the changes appear in females are:
Development of breast
Lighter musculature
Shrill and a higher pitch voice
Broadening of hips due to fat deposition


Word game: Use the clues to work out the words.
Crossword puzzle
Across
Protruding voice box in boys (10)
Glands without ducts (9)
7. Endocrine gland attached to brain (9)
Secretion of endocrine glands (7)
9. Pancreatic hormone (7)
Female hormone (8)
Down
Male hormone (12)
Secretes thyroxine (7)
Hormone reaches here through blood stream (10)
Voice box (6)
Another term for teenager (11)
Term for changes at adolescence (7)
298607.jpg

Across 
3. Adam's apple
4. Endocrine
7. Pituitary
8.Hormone
9.Insulin
10.Estrogen
Down
1. Testosterone
2. Thyroid
5. Target site
6. Larynx
11.Adolescence
12.Puberty


Class 8 Biology Extra Questions