Table of Contents
Students learn about adolescence, changes in adolescence, hormones in adolescence, sexual maturation in boys and girls, and menstrual cycles in Class 8 Science Chapter 10. Puberty, sexual characteristics, the roles of hormones in females, sex determination, and reproductive health are among the subjects covered in Chapter 10 Science Class 8.
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Multiple Choice Questions
- 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.
Answer – (C) Sex chromosomes are passed down from both parents, with each parent contributing one sex chromosome. The father has an XY sex chromosome set, where both chromosomes are active. In contrast, the mother has an XX sex chromosome set, where one chromosome is active.
All children will inherit an X chromosome from their mother, regardless of their gender. This means that the sex of the child is determined by the type of chromosome received from their father. If a child inherits the Y chromosome, they will be a boy. On the other hand, if they receive the X chromosome, they will be a girl.
In summary, the sex of a child is determined by the sex chromosomes inherited from both parents, with the father’s contribution playing a crucial role in determining the child’s gender.
- AIDS can spread from an infected person to another person through:
(a) sharing food
(b) blood transfusion
(c) sharing comb
(d) a mosquito bite
Answer – Acquired Immunodeficiency Syndrome (AIDS) is caused by the Human Immunodeficiency Virus (HIV), which can spread through blood transfusions.
- Given below are events that lead to pregnancy and development of the embryo.
i)Fertilization of egg
ii)Maturation of egg
iii)Release of egg
iv)Embedding of the embryo in the 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
Answer – (d) ii, iii, i, iv.
Explanation – The correct sequence of events that lead to pregnancy and the development of embryos is as follows:
(i) Fertilization of the egg
(ii) Maturation of egg
(iii) Release of the egg
(iv) Embedding of the embryo in the thickened uterine wall
- For the metamorphosis of tadpoles which of the following elements must be available in the water?
(a) chlorine
(b) carbon
(c) sulphur
(d) iodine
Answer – (d) Iodine
Explanation – Metamorphosis is a natural phenomenon observed in various animals like insects, amphibians, and certain aquatic species, where they undergo significant and rapid physical transformations post-birth. The process is triggered by the secretion of thyroxine, facilitated by the thyroid gland’s requirement for iodine.
- The most conspicuous visible change that occurs in boys during puberty is:
(a) development in the voice box.
(b) increase in height.
(c) production of sperms.
(d) increased sweating.
Answer – (b) Increase in height
Explanation – One of the most prominent changes during puberty in boys is the sudden growth in height. This growth spurt is primarily attributed to the extension of long bones, like those found in the arms and legs, leading to an increase in the boy’s overall height.
- 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
Answer – (d) chromosome
Explanation – Inside the cell nucleus, chromosomes are thread-like structures that house genes. A human cell typically contains 23 pairs (46 total) of chromosomes, with 22 pairs being autosomes and one pair being the sex chromosome, responsible for determining the organism’s sex. The presence of XX chromosomes signifies a female, while an XY combination indicates a male.
Very Short Answer Questions
- 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
- 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.
- 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 the adolescence stage.
(d) It marks the beginning of the reproductive period.
Answer – (a) Target site
(b) Sweat glands/salivary glands/oil glands (anyone)
(c) Hormones
(d) Puberty
- Name the hormone that is released by testes at the onset of puberty.
Answer – At the beginning of puberty, the testes release testosterone, which is the hormone responsible for various changes in the body.
- Name the female hormone produced by ovaries that helps in the development of mammary glands
Answer – Produced by the ovaries, estrogen is the female hormone that aids in the development of mammary glands.
Short Answer Questions
- Match the hormones given in Column A with their deficiency disease given in Column B.
| Column A | Column B |
| (a) thyroxine | (i) salt imbalance |
| (b) growth hormone | (ii) diabetes |
| (c) Insulin | (iii) goitre |
| (d) Adrenal hormone | (iv) Dwarfism |
Answer –
| Column A | Column B |
| (a)Thyroxine | (i) Salt imbalance |
| (b) Growth hormone | (iv) Dwarfism |
| (c) Insulin | (ii) Diabetes |
| (d) Adrenal hormone | (i) Salt imbalance |
- 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?
Answer – For optimal health, Lila should incorporate a variety of vitamins and minerals into her diet, in addition to the carbohydrates and proteins she currently consumes. Including more vegetables and fruits in her daily meals will help ensure she receives essential nutrients to stay disease-free.
- Mention any two features that are seen in boys and girls to distinguish them from each other at puberty.
Answer – Two features seen in boys at puberty are:
- Growth of facial hairs
- The voice becomes hoarse.
Two features seen in girls at puberty are:
- Breast development.
- The region below the waist becomes wider.
- We should avoid taking medicines/drugs unless prescribed by a doctor. Give reasons.
Answer – It is crucial to refrain from consuming medications or drugs without a doctor’s prescription, as some drugs can have undesirable side effects that may cause adverse reactions. Furthermore, there is a risk of developing drug addiction, which can negatively impact our health and happiness.
- A few of Paheli’s classmates eat potato chips and burgers regularly during recess at school. Are they healthy eating habits? Give reasons.
Answer – Potato chips and burgers are not considered healthy choices due to their low nutritional value, making them unsuitable for regular consumption.
- Read the statements given below and fill up the blanks with the correct words listed in the box.
deep, ductless, nutrients, thyroxine
(i) The meal that includes all………. is a balanced diet.
(ii) Insufficient production of…………….. in the tadpoles leads to their incomplete development.
(iii) Endocrine glands are also called………….. glands.
(iv) After attaining puberty, boys develop a ………….voice.
Answer- (a) The meal that includes all nutrients is a balanced diet.
(b) Insufficient production of thyroxine in the tadpoles leads to their incomplete development.
(c) Endocrine glands are also called ductless glands.
(d) After attaining puberty, boys develop a deep voice
- Fill in the blank circles in figure 10.1 and identify the sex of children A and B.
Answer –
Lord Answer Questions
- 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) The wider region below the waist
(d) Development of muscles
(e) Development of mammary glands
(f) Growth of facial hair
(g) Acne and pimples on the face
(h) Development of sex organs
(i) High-pitched voice
(j) Growth of pubic hair.
Categorise these changes according to their occurrence in boys and those that occur in girls and fill in the table given below.
Answer –
| Body Changes | |
| Boys | Girls |
| Broad shoulders | The wider region below the waist |
| Wider chests | Development of mammary glands |
| Growth of muscles | Acne and pimples on the face |
| Growth of facial hair | Development of sex organs |
| Acne and pimples on the face | High-pitched voice |
| Development of sex organs | Development of pubic hair |
| Development of pubic hair | |
- In Fig.10.2, mark the positions of 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.
Answer-
- Pituitary gland
- Testis
- Pancreas
- Adrenal gland
- Name the hormone which would be released during the following situations:
(a) a frightened person.
(b) growth of a child to an adult.
(c) development of caterpillar to moth.
(d) development of tadpole to frog.
Answer – (a) Adrenaline is secreted from the adrenal gland during stressful conditions, such as fright, fear, anger, worry, or embarrassment. This hormone prepares the body to function optimally by increasing heart rate and breathing, raising blood pressure, and other responses.
(b) Growth hormone is secreted by the pituitary gland to regulate normal growth in individuals, from childhood to adulthood. A deficiency in childhood can result in dwarfism, while an excess can lead to gigantism.
(c) Insect hormones control the development of a caterpillar into a moth, known as metamorphosis.
(d) Thyroxine is produced by the thyroid gland to control the development of a tadpole into a frog. Iodine in water is essential for its production.
- In human females, each time during maturation and release of the egg the inner wall of the uterus thickens. Is this thickening permanent? Give reasons.
Answer – The thickening of the uterine wall is not permanent. If an egg is fertilized, it begins to divide and form an embryo, which gets embedded in the uterine wall, leading to pregnancy. During pregnancy, no more eggs are released, and the thickened lining is discharged only when the baby is born. However, if fertilization does not occur, the released egg and the thickened lining of the uterus, along with blood vessels, are shed off, resulting in menstruation.
- John and Radha have been classmates since childhood. When Radha was 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?
Answer – Radha’s neck swelling could be attributed to goitre, a condition where the thyroid gland produces an inadequate amount of thyroxine. On the other hand, John’s throat protrusion is likely due to the Adam’s apple bulge, a result of the voice box growth in adolescent boys.
- Salma 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?
Answer – In adolescence, there is an increase in the secretion of sweat from sweat glands and oil from sebaceous glands. The surplus oil and sweat can accumulate in the skin’s small pores, clogging them. Bacteria thrive in these blocked pores, resulting in swelling and redness that can lead to the development of acne and pimples. Maintaining a regular face washing routine helps keep the face clean and dry, aiding in the reduction of pimples.
- 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.
Answer – In our nation, the legal marriage age for girls is 18 years, while for boys it is 21 years. This is because adolescent mothers are not fully prepared, mentally or physically, for motherhood. Early marriage and motherhood can lead to health complications for both the mother and the child. Additionally, early marriage may limit employment opportunities for young women and cause mental distress as they are not yet ready to assume the responsibilities of motherhood. Boys, before reaching adulthood, may not be mentally matured or financially stable enough to shoulder the responsibilities of a family. Therefore, it is advised to delay marriage until a certain age.
- 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?
Answer – A child’s height is primarily influenced by the genes inherited from their parents, but there are additional factors that can impact height. These factors include a balanced diet, hormones, exercise, and overall health. A balanced diet is crucial for adolescents as it provides essential nourishment for the growth of bones, muscles, and other body parts.
Insufficient growth hormones can result in dwarfism, highlighting the importance of hormonal balance. Regular exercise plays a key role in promoting healthy muscles, bones, and joints for proper development. Maintaining good health is vital for growth and is interconnected with the other influencing factors.
Height is determined by a combination of various factors, and any deficiency or absence of these factors can lead to variations. This explains why tall parents may have children of shorter stature, and vice versa.
NCERT Exemplar Solutions for Class 8 Science Chapter 10 – Adolescent Development FAQ’s
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