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

Multiple Choice Questions 

1. The belief that the mother is completely responsible for the sex of the child is wrong because the child 

(a) Gets sex chromosomes 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.  

Ans: (c) Gets one sex chromosome from the mother and the other from the father.  

The father has one X and one Y (XY) sex chromosome, in which both are active, whereas the mother has an XX sex chromosome, in which one is active. 

All children will inherit an X chromosome from their mother, regardless of whether they are a boy or a girl. Thus, the sex of the children will be determined by the type of chromosome received from their father. A child who gets the Y chromosome will be a boy, and a child who gets the X chromosome will be a girl.

2. AIDS can spread from an infected person to another person through 

(a) Sharing food

(b) blood transfusion 

(c) Sharing comb

(d) a mosquito bite 

Ans: AIDS (Acquired Immunodeficiency Syndrome) is caused by Human Immunodeficiency Virus (HIV) that spreads through blood transfusion. 

3. Given below are events that lead to pregnancy and development of embryos.  

(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.

Ans: (d) ii, iii, i, iv.

The sequence of events that lead to pregnancy and development of embryos is as follows:

(ii) Maturation of egg

(iii) Release of the egg

(i) Fertilization of the egg

(iv) Embedding of the embryo in the thickened uterine wall.

4. For the metamorphosis of tadpoles, which of the following elements must be available in water?  

(a) Chlorine 

(b) carbon 

(c) Sulphur 

(d) iodine 

Ans: (d) Iodine 

A biological process by which animals such as insects, amphibians, and a few aquatic animals undergo rapid and extreme physical changes sometime after birth is known as metamorphosis. The thyroid gland needs iodine to secrete thyroxine, which initiates metamorphosis.

5. 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.

Ans: (b) Increase in height 

The sudden increase in height is the most noticeable change during puberty that occurs in boys. Long bones, such as those in the arms and legs, extend during puberty, making the boy taller.

6. Structures present in a cell which is responsible for the determination of the sex of a baby is 

(a) Cytoplasm 

(b) cell membrane 

(c) Nucleus 

(d) chromosome 

Ans: (d) chromosome

Chromosome is a thread-like structure, present inside the nucleus of the cell, which contains genes. There are 23 pairs (46) of chromosomes in a human cell, out of which 222 pairs are autosomes and one pair is the sex chromosome, which determines the sex of the organism. A combination of XX indicates a female and an XY combination indicates a male.

Very Short Answer Questions 

7. Unscramble the underlined words in the following sentences.

(a) Reproductive life of a woman lasts from hacreemn to spauoemen.  

Ans: Menarche, menopause

(b) The development of a caterpillar to an adult butterfly is termed as poommertaissh.  

Ans: Metamorphosis 

(c) The overgrowth of sumselc in xalnyr leads to the hoarse voice in adolescent boys. 

Ans: muscles, larynx 

(d) Dannalier helps the body to adjust and fight the stress.

Ans: Adrenaline

8. Complete the following sentences.

(a) In females, the uterine wall thickens to receive the _______. 

Ans: In females, the uterine wall thickens to receive the fertilized egg.

(b) Endocrine glands release hormones directly into _________ for transportation to the _______.

Ans: Endocrine glands release hormones directly into the bloodstream for transportation to the target site.

(c) The sex hormones __________and estrogen are responsible for the development of ___________ characters. 

Ans: The sex hormones testosterone and estrogen are responsible for the development of secondary sexual characters. 

(d) Release of sex hormones is under the control of a hormone secreted from the ________.

Ans: Release of sex hormones is under the control of a hormone secreted from the pituitary gland.

9. Give a suitable word for each of the following statements.

(a) The site which responds to a hormone.

Ans: Target site

(b) Name of a gland which transports secretions through ducts.  

Ans: Sweat glands/salivary glands/oil glands.

(c) Chemicals which control changes at adolescence stage. 

Ans: Hormones 

(d) It marks the beginning of the reproductive period. 

Ans: Puberty 

10. Name the hormone that is released by testes at the onset of puberty.  

Ans: Testosterone is a sex hormone that is released by the testes at the onset of puberty.

11. Name the female hormone produced by ovaries that helps in the development of mammary glands.  

Ans: Estrogen is the female sex hormone that is mainly responsible for the development of mammary glands. It also regulates the menstrual cycle and helps in the growth of the uterus lining during the menstrual cycle as well as the growth of the pubic and underarm.

Short Answer Questions 

12. Match the hormones given in Column A with their deficiency disease given in Column B. 

Ans: 

13. Lila 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?  

Ans: Lila is not following a balanced diet because her meals do not contain an adequate amount of nutrients. She only consumes carbohydrates and protein in the form of rice and dal. She should include foods rich in vitamins and minerals in her diet to be free from diseases. Therefore, she should eat fruits and vegetables as they are a good source of vitamins and minerals.

14. Mention any two features each that are seen in boys and girls each to distinguish them from each other at puberty.  

Ans: Two features seen in girls at puberty are: 

(i) Development of breasts.

(ii) Hairs grow under the armpit and in the pubic regions.

Two features seen in boys at puberty are:

(i) Facial hair, such as beards and moustaches, grows.  

(ii) Voice becomes deeper (hoarse).

15. We should avoid taking medicines/drugs unless prescribed by a doctor. Give reasons. 

Ans: We should not take medicines or drugs unless agreed by a doctor because some medicines have side effects and have specific dosage levels that, if not followed, may harm the body. Medicines and drugs can be addictive too, which may spoil our health and happiness.

16. A few of Paheli's classmates eat potato chips and burgers regularly during recess at school. Are they healthy eating habits? Give reasons.  

Ans: No, they are not eating healthy food because burgers and potato chips have very little nutritional value and are high in carbohydrates, added sugar, unhealthy fats, and sodium (salt). Eating junk foods such as pizzas, chaat, vada pav, bhajiyas, samosas, burgers, fries, french fries, and rolls regularly is not a healthy eating habit.

17. Read the statements given below and fill up the blanks with the correct words listed in the box.  deep, ductless, nutrients, thyroxine is a balanced diet.

(a) The meal that includes all _________ is a balanced diet.

Ans: nutrients 

(b) Insufficient production _________ in the tadpoles leads to their incomplete development.  

Ans: thyroxine 

(c) Endocrine glands are also called_______ glands.

Ans: ductless 

(d) After attaining puberty boys develop a ________voice.  

Ans: deep

18. Fill the blank circles in figure and identify the sex of child A and B.

Ans: 

Long Answer Questions

19. 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.

Ans: Body changes:

20. In figure mark the positions of the endocrine glands which release the hormones that: 

(a) Controls the release of sex hormones.  

Ans: Pituitary gland

(b) is responsible for the secondary sexual characters in boys.

Ans: Testis 

(c) Prevents diabetes. 

Ans: Pancreas 

(d) Maintains the correct salt balance in the blood.  

Ans: Adrenal gland 

21. Given below are certain food items required for proper nourishment of adolescents. Name the nutrients present in the food items and write their functions.

Ans: The nutrients present in the food items and their functions are as follows: -

22. Name the hormone which would be released during the following situations: 

(a) A frightened person. 

Ans: Adrenaline.

(b) Growth of a child to adult.  

Ans: Growth hormone

(c) Development of caterpillar to moth.  

Ans: Insect hormones.

(d) Development of tadpoles to frogs.  

Ans: Thyroxine.

23. In human females, each time during maturation and release of egg the inner wall of the uterus thickens. Is this thickening permanent? Give reasons.

Ans: No, the thickening of the uterine wall is not permanent. When the egg (female germ cell) is fertilized, it develops into a single-celled zygote and starts multiplying to become an embryo, which travels down the fallopian tube (oviduct) and gets embedded in the uterine. This results in pregnancy. During pregnancy, no more eggs are released. This thickened uterine lining is released after the gestation period of 36 weeks and the baby is expelled from the womb. If fertilization does not occur, the released egg and thickened lining are shed off, resulting in menstruation, or period.

24. 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 diagnosis? 

Ans: Radha's neck may have been swollen because of Goitre. When the thyroid gland is unable to produce an insufficient quantity of thyroxine, the thyroid glands swell, which results in goitre. However, the protrusion on John's throat, on the other hand, could be due to Adam's apple, which causes the voice box to grow in adolescent boys.

25. Observe the chart and graph given in Fig. 10.3 carefully and answer the following questions:

(a) Which of the lines represents the height of boys? 

Ans: The red represents the height of boys as boys' height increases gradually until they reach the age of18, and their percent of full height is lower than girls'.

(b) Which line represents the height of girls?

Ans: Girls have a higher percentage of full height at a particular age than boys, hence the blue line represents their height.

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

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

(d) Is this pattern true for each individual?  

Ans: Some grow quickly at the initial stages, then slow down. However, some people develop slowly and reach their full height by the age of 18. The rate of growth in height varies among individuals, so this pattern is not true for each individual. 

26. Salma had 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?  

Ans: After adolescence, the activity of sweat glands (also known as sudoriferous or sudoriferous glands) and sebaceous glands (small oil-producing glands) increases their secretion, leading to the release of more oil and sweat, which gets collected in the pores of the skin, thus the pores get blocked. Bacteria grow there, leading to the development of pimples on the face. 

As Salma entered adolescence, her sweat glands and sebaceous glands increased their secretion, which resulted in the pimples on her face. If Salma washed her face regularly and kept it clean and dry, she would be able to get rid of her pimples.

27. Our government has legalized the age for marriage in boys and girls. Give reasons as to why one should get married after a certain age.  

Ans: In India, girls must be 18 years old to marry, while boys must be 21 years old. According to the Prohibition of Child Marriage Act, a girl and a boy cannot marry before the age of 18 and 21 in India, respectively. Some complications related to early marriages are: 

(i) Early marriage and motherhood are associated with health issues for both the mother and the child because girls are neither physically nor mentally ready to go through motherhood. 

(ii) This limits the young woman's employment opportunities and may create mental anguish because she is not yet ready to take on motherhood's responsibilities.

(iii) The boys, before 18 years of age, may not be mentally mature and financially secure enough to carry out fatherhood. 

28. It is believed that the 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?  

Ans: Yes, though height is a genetic trait, it depends upon genes inherited from parents, but it also depends on various factors that affect the height of a child. These include the type of nutrients we take, the type of exercise we do, the amount of growth hormones secreted in a person, diseases they suffer from, etc. 

If a child's diet lacks the necessary nutrients, it will affect his growth and development, as various nutrients help in the formation of bones, muscles, and tissues. Similarly, in children, if growth hormone is not secreted appropriately by the pituitary gland, stunted growth (dwarfism) or overgrowth (gigantism) can occur. For healthy bone and muscular development, proper and consistent exercise is essential. Certain diseases can also lead to abnormal body growth and development. As a result, these factors influence a person's height.

Chapter 10 Reaching the Age of Adolescence

NCERT Exemplar Class 8 Science Solutions Chapter 10 Reaching the Age of Adolescence is a book specifically curated for students to solve the questions provided in the exemplar exercises easily. In chapter 10 of Class 8, students will mostly be learning all about adolescence and puberty, which includes the changes that occur in boys and girls during the time of puberty. Students also become aware about the secondary sexual characters that are developed during this time period and the role of hormones that initiates the reproductive functions and harmful effect of drugs. The questions that are mentioned in the NCERT Exemplar Class 8 Science Solutions Chapter 10 Reaching the Age of Adolescence are of both objective and subjective types. Vedantu has made it possible to learn more about the topic by focusing on the exam preparation. 

Puberty

Puberty is the stage in a person's life when their body and reproductive systems undergo changes that lead to sexual maturity. The most significant change that occurs throughout puberty is that boys and girls become reproductively competent. Puberty can start a year or two earlier in females than in boys.

Changes in puberty

During the commencement of puberty, a person goes through a variety of changes. It varies between males and females, along with the magnitude of these alterations in each individual. Each person goes through changes such as height gain, bodily form change, voice change, sex organ growth, and mental, intellectual, and emotional maturation.

Secondary Sexual Characteristics

External, visible traits emerge in boys and girls during puberty, aid in sex differentiation, and are unrelated to reproduction. The following are the secondary sexual characteristics:

Boys

The development of facial, underarm, abdomen, chest, and pubic hair development are all examples of body hair growth. The chest and shoulders expand, and the body develops muscle. Skin becomes more rough and porous, and perspiration and sebaceous gland secretions rise. The larynx (Adam's apple)/voice box protrudes, resulting in a deep, husky voice.

Girls

Breast enlargement, body hair development, particularly in the underarm and pubic regions, and hips enlargement are some of the changes. Fat distribution has shifted. More fat beneath the skin, particularly in the hips, buttocks, and thighs. Secondary reproductive organs are developing.

Reproductive Health

An individual's health is defined as their bodily and mental well-being. The reproductive organs grow and become functioning during adolescence. The proper growth and well-being of the reproductive organs are referred to as reproductive health.

Endocrine Glands

An endocrine system is a collection of ductless glands that secrete chemical molecules called hormones to control physiological processes and function in various systems. They immediately inject their secretions into the circulation. Hormones frequently have a long distance between their source and the location of the action.

Testosterone

The predominant male sex hormone is testosterone.

It is also responsible for the development of secondary sexual traits, the development of male reproductive organs, and also the generation of male gametes, such as sperms. Only during puberty does the testes begin to secrete testosterone.

Estrogen

The predominant female sex hormone is estrogen/oestrogen. It is in charge of developing female reproductive organs, the creation of female gametes (ova), secondary sexual traits, and the menstrual cycle. After puberty, the ovaries release this hormone.

Thyroid Gland

The gland is shaped like a butterfly and is located in the neck. The thyroid gland secretes thyroxine, a hormone. This hormone is vital because it keeps all metabolic functions in check. A lack of this hormone can cause the thyroid gland to enlarge, resulting in goitre.

Pancreas

The pancreas is an abdominal organ surrounded by the spleen, liver, and small intestine, and is placed behind the stomach. It is an essential element of the digestive system that regulates blood sugar levels.

Pancreatic enzymes like amylase, proteases, and lipases enter the duodenum during digestion. These enzymes aid in the digestion of sugar, proteins, and lipids. The pancreas contains islets of Langerhans, which produce hormones like insulin and glucagon into the bloodstream.

Menstrual Cycle

It is a female reproductive cycle. Menarche, or the start of the menstrual cycle, occurs during puberty. The process involves cyclic changes in both the ovaries and the uterus, which occur simultaneously. An ovum grows and matures in the ovaries before being expelled. A thick spongy inner lining develops in the uterus in preparation for pregnancy. Pregnancy happens when the egg is fertilised. If fertilisation does not occur, the free egg and the thicker uterine lining and blood vessels are lost. Menstruation is the bleeding that women experience as a result of this. Women's menstrual cycles end between the ages of 45 and 52. Menopause occurs when a woman's menstrual cycle ends. Between menarche and menopause, a woman's reproductive age is determined by her ability to have children.

Personal Hygiene

Personal cleanliness is crucial, especially throughout adolescence. Overactive sweat glands can make the body smell bad. Acne is also a result of it. Everyday, all portions of the body should be cleaned. There is a risk of contracting bacterial and fungal illnesses if hygiene is not maintained.

Balanced Diet

Adolescence also refers to a period of rapid physical growth. All of the nutrients are required by a developing body. As a result, all teens should eat a well-balanced diet rather than junk food. A balanced diet is a meal that has the right amounts of proteins, carbs, fats, and vitamins. Junk food has an impact on a person's development.