Ncert revision notes chapter 10 reaching the age of adolescence class 8 science.
• Adolescence
→ Increase in height
→ Change in body shape
→ Change in the voice pattern
→ Change in activity of sweat and sebaceous glands
→ Change in sex organs
→ Change in intellectual level
• Secondary sexual characteristics in boys
• Secondary sexual characteristics in girls
→ Characteristics of hormones
• Endocrine glands
→ Pituitary gland
→ Thyroid gland
→ Parathyroid gland
→ Adrenal gland
• Historical background and discovery of HIV
→ Structure of HIV
→ Transmission of HIV
→ Prevention of HIV
→ Tests for detection of HIV
• Personal health and hygiene in adolescents
• Sex determination in humans
→ The time period when the body undergoes changes to reach reproductive maturity is known as
adolescence.
→ It begins around the age of 11 and lasts till about 18 or 19 years of age.
→ Adolescence in girls can begin one or two years earlier than boys.
→ The various changes that occur in the body during adolescence marks the onset of puberty.
→ Puberty ends when teenagers attain sexual maturity.
→ Changes that take place during puberty
Increase in height
→ It is caused by the growth in long bones of the arms and legs.
→ Girls grow faster than boys initially but both reach their maximum height by the age of 18
Change in body shape
→ Boys develop broader shoulders, wider chests, and prominent muscles.
→ In girls the region below the waist becomes wider.
Change in the voice pattern
→ Voice box or larynx starts growing during puberty.
→ It protrudes in males in the neck region and is called Adam’s apple.
→ Boys develop deep low-pitched voice.
→ Girls develop high-pitched voice.
Change in activity of sweat and sebaceous glands
→ The activity of sweat glands increases during puberty, resulting in production of more sweat.
→ The oily secretions from sebaceous glands increase. The accumulation of oil and bacterial action leads to acne problems in teenagers.
Changes in sex organs
→ Testes and penis develop completely in boys.
→ Testes start producing sperms.
→ Ovaries develop completely and start producing eggs in girls.
Change in intellectual level
→ The learning capacity of brain increases.
→ Intellectual development takes place during adolescence.
→ Development of secondary sexual characteristics.
→ Appearance of moustaches and beard.
→ Appearance of hair on chest.
→ Growth of hair in genital area and other parts.
→ Increase in breast size
→ Growth of hair in the pubic region.
→ Hormones are chemical secretions that bring about various changes in the body.
→ They are produced by endocrine glands.
→ These glands release hormones into blood to reach specific target site.
→ Production of hormones is under the control of hormones produced from pituitary gland.
Characteristics of hormones
→ Hormones act as chemical messengers.
→ They are secreted by living cells/tissues or organs called glands.
→ They are secreted in very small quantities by glands.
→ They act upon specific cells, tissues, or organs called the target sites.
→ They are generally slow in action, but have long lasting effects.
→ They either accelerate or inhibit a reaction.
→ Hormones are secreted by endocrine glands such as the pituitary gland, thyroid gland, adrenal gland, pancreas etc.
• Major endocrine glands in humans are
(i) Pituitary
(ii) Hypothalamus
(iii) Pineal
(iv) Thyroid
(v) Parathyroid
(vi) Thymus
(vii) Pancreas
(viii) Adrenal
(ix) Testis in men /ovary in women
→ A feedback mechanism (positive and negative) regulates the action of the hormones.
Pituitary gland
→ It is a pea sized gland situated at the base of the brain. It secretes a growth hormone (GH).
→ It is required for proper body growth.
→ The hyposecretion of growth hormone causes a condition called dwarfism.
→ The hypersecretion causes gigantism in children and acromegaly in adults.
Thyroid gland
→ It is located close to trachea in the neck. It produces a hormone called thyroxine.
→ It is required for regulating metabolism in the body.
→ The hyposecretion of thyroxine causes hypothyroidism.
→ This condition causes abnormalities like simple goitre, myxoedema and cretinism.
→ Lack of iodine leads to deficiency of thyroxine, which results in a disease called goitre.
→ The excess secretion of thyroxine causes hyperthyroidism. It results in high metabolism, protrusion of the eye balls, high BP, nervous tension, etc.
Parathyroid Gland
→ There are four parathyroid glands present on back side of thyroid glands that secrete parathyroid hormone or parathormone (PTH).
→ This hormone regulates the level of calcium ions in the bloodstream.
→ Excess of parathyroid hormone removes calcium from bones and makes them soft.
→ It produces two hormones- Insulin and Glucagon.
→ These hormones maintain blood sugar level.
→ Deficiency of insulin results in diabetes.
Adrenal Gland
→ There are two adrenal glands located one on upper part of each kidney.
→ It has two parts- cortex and medulla.
→ Cortex secretes the hormones like cortisol that regulates the rate of metabolism.
→ The medulla secretes a hormone like adrenaline that prepares the body to face various stressful situations.
→ It includes testes in males and ovaries in females.
→ Male sex hormone is testosterone. It is produced by the testes on the onset of puberty.
→ Female sex hormones produced by ovaries are estrogen and progesterone.
→ Deficiency of estrogen causes infertility.
→ Process of Hormonal Action
→ Endocrine glands release their secretions (hormones) into the bloodstream.
→ Hormones, on reaching their target site, bring about necessary changes to maintain proper functioning of the body.
→ The first cases of AIDS were recognized in U.S.A in the year 1981.
→ The AIDS virus was first discovered by the team of French scientists lead by Luc Montagnier in1983.
→ In 1984, the American virologist named Robert Charles Gallo gave the first report on the virus causing AIDS.
→ The name HIV was suggested by the International committee on the nomenclature of viruses.
→ In India the firsts AIDS patient was identified in Chennai in the year 1987.
→ AIDS or Acquired Immune deficiency syndrome is a viral disease, caused by the deadly virus (HIV).
Structure of HIV
→ Human Immunodeficiency virus (HIV) is spherical in shape and contains RNA as its genetic material.
→ Externally, the virus is covered by the double layered membrane made up of fatty substances.
→ Inside the fatty membrane a core of proteins is found that surrounds the viral RNA along with the enzyme reverse transcriptase.
Transmission of HIV
→ Sharing of syringes during drug abuse.
→ Unsafe sexual contact.
→ Transfusion of infected blood
→ From infected mother to her infant through milk.
Prevention of HIV
→ Avoid sexual contact with infected persons
→ Ensure use of disposable syringes
→ Screening blood from blood banks
Tests for detection of HIV
→ PCR (Polymerase Chain Reaction)
→ ELISA (Enzyme linked Immuno Sorbent Assay)
→ Western Blot
→ Adolescents should have a balanced diet with right proportions of various nutrients.
→ Adolescents should maintain cleanliness to prevent bacterial infections.
→ They should indulge in some physical exercises to keep their bodies fit.
→ They should avoid the consumption of drugs and alcohol.
• Autosomes: First 22 pairs of chromosomes that do not determine the sex of an individual.
• Sex chromosomes: Last pair of chromosomes, represented as X and Y.
→ Females have two X chromosomes,so can be represented as 44+XX.
→ Males have one X and one Y chromosome, so can be represented as 44+XY.
→ Each gamete receives half of the chromosomes i.e. 22+X or 22+Y.
→ Male gametes have 22 autosomes and either X or Y sex chromosome.
→ Male gametes can be of two types, 22+X or 22+Y.
→ Female gametes can be of only one type, 22+X.
→ Sex of a baby is determined by the type of the male gamete (X or Y) that fuses with the female gamete.
Related chapters.
NCERT Solutions for Class 6, 7, 8, 9, 10, 11 and 12
October 11, 2019 by Sastry CBSE
Question 1. What is Adam’s apple? Answer: The protruding part of the throat in males is called Adam’s apple.
Question 2. Name the hormone in female that is produced by ovaries and helps in development of mammary glands. Answer: Estrogen
Question 3. Whose height grow faster initially—boys or girls? Answer: Girls
Question 4. Name a gland which transports secretions through ducts. Answer: Sweat glands/salivary glands/ oil gland (any one).
Question 5. What is puberty? Answer: The age at which boys and girls become capable of reproduction.
Question 6. What are hormones? Answer: The chemical substances produced by endocrine glands are called hormones.
Question 7. How long is a woman’s reproductive life lasts? Answer: Menarche to menopause.
Question 8. Name the female hormone. Answer: Estrogen
Question 9. Which gland is called master gland? Answer: Pituitary gland
Question 10. What is a balanced diet? Answer: The meal that includes all nutrients is called a balanced diet.
Question 11. What is menstruation? Answer: Extrusion of uterus lining and blood along with the unfertilised egg from the vagina is called menstruation.
Question 12. What is menarche? Answer: The first menstrual flow begins at puberty and is termed as menarche.
Question 13. What is menopause? Answer: Stoppage of menstruation is called menopause.
Question 14. What causes goitre? Answer: Deficiency of thyroxine hormone.
Question 15. Which gland secretes thyroxine? Answer: Thyroid gland
Question 16. What are chromosomes? Answer: The thread-like structures in the nucleus are called chromosomes.
Question 17. How many chromosomes are present in human cell? Answer: 23 pairs or 46 chromosomes.
Question 18. How many sex chromosomes are there in human cell? Answer: Two, i.e., one pair.
Question 19. Which hormone is necessary for normal growth of a person? Answer: Growth hormone.
Question 20. Which gland secretes insulin? Answer: Pancreas
Question 21. What causes diabetes? Answer: Deficiency of insulin.
Question 22. Name the chromosome present in a female. Answer: X chromosome
Question 23. Name the chromosome present in a male. Answer: X and Y chromosomes
Question 24. Which chromosome does the unfertilised egg contain? Answer: X chromosome
Question 25. Which hormone balances the proportion of salts in the blood? Answer: Adrenaline
Question 26. What decides the sex of an unborn child? Answer: Sex chromosome of father.
Question 27. Name the glands other than the pituitary gland. Answer: Thyroid, pancreas and adrenals.
Question 28. When does the puberty ends? Answer: uberty ends when an adolescent reaches reproductive maturity.
Question 29. Do the boys and girls undergo same physical changes at puberty? Answer: No
Question 30. Why do we need to have a balanced diet? Answer: To keep the body healthy.
Question 1. What is meant by adolescence? Answer: Growing up is a natural process. The period of life, when the body undergoes several changes leading to reproductive maturity, is cabled adolescence. The adolescence period is 11 to 19 years of age.
Question 2. What is puberty? Answer: The period during which adolescent boys and girls attain sexual maturity and become capable of reproduction is called puberty. Puberty age of female is 10 to 12 years while male puberty age is 12 to 14 years.
Question 3. What is vital change which marks puberty in boys and girls? Answer: During puberty, the human body undergoes several changes, but the most important changes which marks puberty is that boys and girls become capable of reproduction.
Question 4. Why do boys have a hoarse voice at puberty? Answer: The voice box or larynx begins to grow at the onset of puberty. This growing voice box in boys can be seen as a protruding part of the throat called Adam’s apple. This leads to voice becoming hoarse.
Question 5. How does the body shape change at puberty? Answer: Body shape changes differently in boys and girls at puberty. Boys have broader shoulders and wider chests. Their muscles grow more prominently than girls. In girls, the region below the waist becomes wider.
Question 6. Why is adolescence also called teenage? Answer: Adolescence period is generally 11 to 19 years of age. Because the period covers the teens, i.e., 13 to 19 years of age, adolescents are also called teenagers.
Question 7. Why do many young people have acne and pimples during adolescence? Answer: During puberty the secretion of sweat glands and sebaceous glands (oil glands) increases. It develops acne and pimples on the face of young boys and girls.
Question 8. Why are endocrine glands also called ductless glands? Answer: Endocrine glands release hormones directly into the blood stream. So, they are termed as ductless glands. For example, pituitary, thyroid, pancreas, etc.
Question 9. What are secondary sexual characters? Answer: At puberty, in girls, breasts begin to develop, the region below the waist become wider, voice become shriller. Boys begin to grow facial hair, i.e., moustache and beard. Boys also develop hair on their chest, the muscles of the body grow more prominently, develop larger voice box which can be seen as a protruding part of the throat called Adam’s apple. In both boys and girls, hair grows under the arms and in the pubic region. As these features distinguish the male from the female they are called secondary sexual characters.
Question 10. Explain the development of sex organs in male and female. Answer: The male and the female sex organs develop completely at puberty. Male sex organ like testes and penis develop completely. The testes begin to produce the male gametes or sperm. Similarly in girls the ovaries enlarge and egg begins to mature. Ovaries start releasing matured eggs or ovum.
Question 11. Why do changes occur in human body at puberty? Answer: The changes in human body at puberty occur due to release of hormones by different types of glands. Hormones are chemical substances secreted from endocrine glands or endocrine system. Male hormone or testosterone are responsible for changes in male whereas female hormone or estrogen are responsible for changes in female.
Question 12. What is a pituitary gland? Answer: Different types of hormones are secreted by different types of glands. The product of all these hormones is under the control of another hormone secreted from an endocrine gland called pituitary gland.
Question 13. How do hormones work in human body? Answer: Endocrine glands release hormones into the blood stream to reach a particular body part called target site. The target responds to the hormone. There are many endocrine glands or ductless glands in the body.
Question 14. What are sex hormones? How do they work in the human body? Answer: Sex hormones help boys and girls develop sex organs to enable them for reproduction. These hormones lead them to reproductive maturity.
In girls, estrogen makes the breasts develop. Milk secreting glands or mammary glands develop inside the breasts. Ovaries begin to produce eggs. In boys, testosterone is released by testes. Testes begin to release sperms. Changes in boys is also seen due to this hormone.
Question 15. What is menstruation? Answer: At puberty, in girls the ovaries get enlarged and start producing eggs (ovum). One egg matures and is released by one of the ovaries once in about 28 to 30 days. During this period, the wall of the uterus becomes thick so as to receive the egg. If the egg is fertilised then it begins to develop and results in pregnancy. If this egg is not fertilised, the released egg and thickened lining of the uterus along with its blood vessels are shed off causing bleeding in female which is called menstruation. It occurs once in about 28 to 30 days.
Question 16. What are the changes in female at the onset of puberty? Answer: There are several changes in females at the onset of puberty. They are:
Question 17. Explain the terms menarche and menopause. Answer: The first menstrual flow begins at puberty and is termed as menarche. At 45 to 50 years of age, the menstrual cycle stops. Stoppage of menstruation is called menopause.
Question 18. What happens when the egg is fertilised? Answer: When the egg is fertilised, it begins to divide and then gets embedded in the uterus for further development. Finally the fertilised egg develops into a foetus.
Question 19. What are the changes in males at puberty? Answer: There are various changes in males at puberty. They are:
Question 20. What do you mean by reproductive health? Answer: The physical and mental well being of an individual is regarded as an individual’s health. To keep the body healthy, every human being, at any age, needs to have a balanced diet. The person must also observe personal hygiene and undertake adequate physical exercise.
Thus, reproductive health refers to the diseases, disorders and conditions that affect the functioning of the male and female reproductive system during all stages of life.
Question 21. What is the role of hormones in completing the life history of insects and frogs? Answer: Hormones play an important role in the completion of life cycle of insects and frogs. Metamorphosis in insects is controlled by insect hormones. In a frog, it is controlled by thyroxine, the hormone produced by thyroid gland. Thyroxine production requires the presence of iodine in water. Water in which iodine is not, present, the tadpoles cannot become adult.
Question 22. Which hormone is released by pancreas? What is its function? Answer: Insulin is released by pancreatic gland. It regulates sugar metabolism. If insulin is deficient in the body, sugar level becomes high in blood causing diabetes.
Question 1. What changes occur in human at puberty? Answer: There are various changes in human at puberty. They are as follows:
Question 2. Explain the reproductive phase of life in humans. Answer: Boys and girls become capable of reproduction at puberty because their testes and ovaries begin to release gametes, i.e., sperms and ova respectively. In girls, reproductive phase of life begins at puberty from 10 to 12 years of age and generally lasts till the age of 45 to 50 years. The ova begin to mature with the onset of puberty. The ovum matures and is released by one of the ovaries once in 28 to 30 days.
During this period, the wall of the uterus becomes thick so as to receive the egg, in case it is fertilised and begins to develop. This results in pregnancy. 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 menstruation. It occurs once in about 28 to 30 days. The first menstrual flow begin at puberty and is termed as menarche. The menstruation stops at the age of 45 to 50. This stage is known as menopause. In male, the reproductive phase begins at puberty at the ages 14-15 and lasts as long as he is healthy.
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. Fig. 10.5 shows sex determination in humans.
Question 5. Explain the term reproductive health. What should we do to maintain reproductive health? Answer: The state of physical, mental and social well being of an individual is regarded as an individual’s health. A healthy person is free from disease, tension and anxiety. Reproductive health refers to a state of physical, mental and social well-being in all matters relating to the reproductive system, at all stages of life. We should take following measures to maintain reproductive health:
Question 1. One day Seema’s uncle visited her place. Seema prepared dinner for him. When she was about to put rock salt on the salad, her uncle interrupted her and asked to put iodised salt instead of rock salt. He also advised her to prefer iodised salt instead of rock salt. Why do you think Seema’s uncle advised her to have iodised salt instead of rock salt? Answer: Deficiency of iodine causes goitre disease in our body. This is why Seema’s uncle advised her to have iodised salt.
Question 2. It is said that height of a child depends upon the genes inherited from the parents. Are there factors other than genes that causes variation in height? Answer: Other factors like nutrition, release of growth hormones, exercises, diseases, etc., also have impact on the height of a growing child.
Question 3. Is a woman responsible for the birth of a girl child? Explain. Answer: No, because a woman has eggs of only X chromosomes but a male has sperms of both X and Y chromosomes. It is the type of male chromosome (X or Y) which fuses with the egg and determine the sex of the foetus, i.e., whether it will be male (XY) or female (XX) child.
Question 4. 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? Answer: The swelling on the neck of Radha may be because of insufficient production of thyroxine which results in goitre. However slight protrusion in John’s throat may be due to enlargement of voice box, also known as Adam’s apple, in adolescent boys.
Question 5. Why we should not take medicines or drugs unless prescribed by a doctor? Answer: Certain medicines have specific dosage levels and adverse side effects which if not followed may be proved lethal to us. Drugs can be addictive too and can ruin our health and happiness.
Question 1. Salma had a very soft and smooth skin during her childhood. As she entered adolescence, she developed pimples on her face, her body became taller compared to her face. She got worried of all of the sudden changes. Her mother explained that all these changes are normal and advised her to wash her face at regular intervals.
Activities and Projects Question 1. Find out from your elder relatives about their awareness of the legal status of early marriage. You yourself may get information on it from your teacher, parents, a doctor or the internet. Write a two minute speech explaining why early marriage is not good for the couple. Answer: Our law does not permit the marriages of girls below 18 years of age and the boys below 21 years. Biologically also, it is not good for both boys and girls. Early marriages are not good for the couple due , to following reasons:
Question 2. Collect newspaper cuttings and information in magazines about HIV/AIDS. Write a one page article of 15 to 20 sentences on HIV/AIDS. Answer: Introduction: Acquired Immune Deficiency Syndrome (AIDS) is a spectrum of conditions caused by infection with the human immunodeficiency virus (HIV). It may also be referred to as HIV disease or HIV infection. Following initial infection, a person may experience a brief period of influenza-like illqess. This is typically followed by a prolonged period without symptoms. As the infection progresses, it interferes more and more with the immune system, making the person much more susceptible to common infections, like tuberculosis, as well as opportunistic infections and tumors that do not usually affect people who have working immune systems. The late symptoms of the infection are referred to as AIDS. This stage is often complicated by an infection of the lung known as pneumocystis pneumonia, severe weight loss, skin lesions, or other AIDS-defining conditions.
Transmission: HIV is transmitted primarily via unprotected sex, contaminated blood transfusions,- hypodermic needles, and from mother to child during pregnancy, delivery, or breastfeeding. Some bodily fluids, such as saliva and tears, do not transmit HIV.
Prevention: Common methods of HIV/AIDS prevention include encouraging and practicing safe sex, needle-exchange programs, and treating those who are infected. There is no cure or vaccine; however, antiretroviral treatment can slow the course of the disease and may lead to a near-normal life expectancy.
Question 3. In our country, according to 2011 census, there are 940 adolescent females for every 1000 males. Find out (a) the concerns of the community regarding this low ratio. Remember that the chance of having a boy or a girl is equal. (b) what amniocentesis is and how useful this technique is. Why is its use for identification of sex of the unborn child banned in India? Answer: (a) For a long, our society has been male dominated. There is also a belief that only the son can contin¬ue the lineage and the daughter is other’s property (paraya dhan). This belief leads to girl foeticide as in most cases, people want a son. This results in low sex ratio. (b) Amniocentesis is a medical procedure used in prenatal diagnosis of chromosomal abnormalities, foetal infections and sex determination. For this a small amount of amniotic fluid, which contains foetal tissues, is sampled from the amniotic sac surrounding a developing foetus using a needle. In India, selective abortion of female foetuses due to preference of male child has enforced Indian Government to ban sex-determination through amniocentesis.
Question 4. Put your ideas together and write a short note on the importance of knowing facts about reproduction. Answer: Sex education or knowing facts about reproduction is very important due to the following reasons:
I.Multiple Choice Questions (MCQs) Choose the correct option. Question 1. The adolescence period is (a) 14 – 20 years (b) 10 – 18 years (c) 11 – 19 years (d) none of these
Question 2. Larynx is called (a) music box (b) voice box (c) respiratory organ (d) sound box
Question 3. Most adolescents attain their maximum height around the age of (a) 22 – 25 years (b) 13-15 years (c) 11 – 12 years (d) 18 – 19 years
Question 4. Initially girls grow (a) slower than boys (b) faster than boys (c) both of these (d) none of these
Question 5. Puberty age in females is (a) 10 – 12 years (b) 12 – 14 years (c) 8-10 years (d) 5-6 years
Question 6. Puberty age in males is (a) 12 – 14 years (b) 13 – 15 years (c) 10 – 12 years (d) 18 -20 years
Question 7. Thyroxine hormone is produced by (a) adrenal gland (b) testes (c) pituitary gland (d) thyroid gland
Question 8. The male hormone is called (a) estrogen (b) testosterone (c) thyroxine (d) insulin
Question 9. The female hormone is called (a) estrogen (b) testosterone (c) adrenaline (d) none of these
Question 10. Menstruation occurs once in about (a) 28 to 30 days (b) 25 to 30 days (c) 45 to 50 days (d) none of these
Question 11. The number of chromosomes present in human cell are (a) 25 pairs (b) 22 pairs (c) 23 pairs (d) none of these
Question 12. The number of sex chromosomes are (a) three (b) two (c) four (d) none of these
Question 13. The age of menopause stage is (a) 45 to 50 years (b) 40 to 45 years (c) 50 to 55 years (d) none of these
Question 14. The unfertilised egg always has __________ chromosome (a) X (b) Y (c) XY (d) XX
Question 15. A female has (a) XY chromosomes (b) YY chromosomes (c) XX chromosomes (d) none of these
Question 16. The gametes have only (a) one set of chromosomes (b) two sets of chromosomes (c) three sets of chromosomes (d) none of these
Question 17. Which of the following is male gonads? (a) Moustache (b) Chest (c) Testes (d) Hair
Question 18. Production of thyroxine requires (a) magnesium (b) iodine (c) sodium (d) bromine
Question 19. Which of the following determines the sex of the baby? (a) Chromosomes (b) Chloroplast (c) Hormones (d) Pituitary gland
Question 20. Pancreas is responsible for maintaining (a) blood pressure (b) fat metabolism (c) blood glucose level (d) electrolyte balance Answer: 1. (c) 2. (b) 3. (d) 4. (b) 5. (a) 6. (a) 7. (d) 8. (b) 9. (a) 10. (a) 11. (c) 12. (b) 13. (a) 14. (a) 15. (c) 16. (a) 17. (c) 18. (b) 19. (a) 20. (c)
II. Fill in the Blanks Fill in the blanks with suitable word/s. 1. ___________ means to grow into maturity. 2. Children gain height during ___________. 3. The boys and girls passing through the adolescence period are called ___________ or ___________. 4. During puberty, a change in voice takes place due to the increase in the size of ___________ or ___________. 5. The stage when the menstrual cycle stops is called ___________. 6. The ___________ gland helps in controlling the production of both testosterone and estrogen hormones. 7. Diabetes is caused due to the deficiency of ___________ in the body. 8. ___________ is caused due to deficiency of thyroxine hormone. 9. Endocrine glands are also called ___________ glands. 10. ___________ secrets male sex hormones. 11. ___________ secrets female sex hormones. 12. Sex of the unborn child depends on whether the ___________ has ___________ or ___________ chromosomes. 13. Metamorphosis in insects is controlled by ___________ hormone. 14. Metamorphosis in frog is controlled by ___________ hormone. 15. If the water in which tadpoles are growing does not contain sufficient ___________, the tadpoles cannot become adults. 16. In females, the uterine wall thickens to receive the ___________. 17. Endocrine glands release hormones directly into the ___________ for transportation to the ___________. 18. ___________ helps the body to adjust and fight the stress. 19. The development of a caterpillar to an adult butterfly is termed as ___________. 20. The first menstrual flow begins at ___________ and is termed as ___________. Answer: 1. Adolescence 2. puberty 3. adolescents, teenagers 4. voice box, larynx 5. menopause 6. pituitary 7. insulin 8. Goitre 9. ductless 10. Testes 11. Ovary 12. zygote, XX, XY 13. insect 14. thyroxine 15. iodine 16. zygote 17. blood stream, target site 18. Adrenaline 19. metamorphosis 20. puberty, menarche 18. Adrenaline
IV, True or False State whether the given statements are true or false. 1. The age of adolescence is 15 to 20 years. 2. The female puberty starts at the age of 12 to 14 years. 3. Boys have enlarged and well developed Adam’s apple. 4. Insulin is secreted by pituitary gland. 5. The chemical substances secreted by endocrine glands are called hormones. 6. . Estrogen is female hormone. 7. Testosterone is male hormone. 8. There are 23 pairs of chromosomes in the nuclei of human cell. 9. Menstruation stops in men permanently around the age of 45 to 50 years. 10. The estrogen hormone develops deeper voice in males at puberty. 11. The sex of an unborn child is determined after a foetus is formed. 12. Initially girls grow faster than boys. 13. Thyroxine hormone is released by thyroid gland. 14. Diabetes is caused due to the deficiency of adrenaline hormone. 15. Menstrual cycle in women is controlled by enzyme. 16. Growth hormones are secreted by pituitary glands. 17. Metamorphosis in insects are controlled by growth hormone. 18. Menstruation occurs once in about 28 to 30 days. 19. There are 3 sex chromosomes present in the nuclei of human being. 20. A male has two X chromosomes. 21. The gametes have only one set of chromosomes. 22. The unfertilised egg has two X chromosomes. 23. At puberty, the voice box or the larynx begins to grow. 24. When the zygote has one X and one Y chromosome, a male child is developed. 25. Menopause is the stage when menstruation starts. Answer: 1. False 2. False 3. True 4. False 5. True 6. True 7. True 8. True 9. False 10. False 11. False 12. True 13. True 14. False 15. False 16. True 17. False 18. True 19. False 20. False 21. True 22. False 23. True 24. True 25. False
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Class 8 Science Chapter 10 Reaching the Age of Adolescence MCQ (Multiple Choice Questions) with Answers is available here in PDF format. CBSE Class 8 Science Reaching the Age of Adolescence Objective Questions helps the students to understand the concepts thoroughly and to score good marks. Practising these MCQs will help you to answer every question that is being asked in the exams.
At Study Path, you can download PDF of Multiple Choice Questions for Class 8 Chapter 10 Reaching the Age of Adolescence with Answers. Our expert teachers prepared these MCQs on the basis latest exam Pattern. Students can solve these NCERT MCQs before the exam to know their preparation level.
Multiple Choice Questions (MCQs)
Question 1. Adolescence is the period of
(a) 5 to 10 years (b) 11 to 19 years (c) 22 to 28 years (d) 30 to 40 years
Answer: (b) 11 to 19 years
Question 2. When a sperm having X-chromosome fuses with the ovum, the child born will be
(a) male (b) female (c) male as well as female twin (d) it depends on the chance of fusion
Answer: (b) female
Question 3. How many pairs of Chromosomes are found in nuclei of their cells?
(a) 22 pairs (b) 23 pairs (c) 24 pairs (d) 25 pairs
Answer: (b) 23 pairs
Question 4. Children gain height during
(a) adolescence (b) endocrine (c) balanced food (d) menarche
Answer: (a) adolescence
Question 5. Testes secrete
(a) thyroxin (b) estrogen (c) testosterone (d) iodine
Answer: (c) testosterone
Question 6. Adam’s apple is
(a) enlarged larynx (b) mammary glands (c) apple of adam (d) red apple
Answer: (a) enlarged larynx
Question 7. The chemical substances which are secreted from endocrine glands are called
(a) puberty (b) hormones (c) estrogen (d) adolescence
Answer: (b) hormones
Question 8. Out of these which one determines the sex of the baby?
(a) Hormones (b) Chloroplast (c) Chromosomes (d) Pituitary gland
Answer: (c) Chromosomes
Question 9. What is the stoppage of menstruation called?
(a) Menarche (b) Menopause (c) Gametes (d) Insulin
Answer: (b) Menopause
Question 10. Which hormone is secreted by adrenal glands?
(a) Adrenalin (b) Insulin (c) Testosterone (d) Estrogen
Answer: (a) Adrenalin
Question 11. Reproduction age in women starts when their
(a) menstruation starts (b) breasts start developing (c) body weight increases (d) height increases
Answer: (a) menstruation starts
Question 12. Which is male gonads?
(a) Hair (b) Chest (c) Moustache (d) Testis
Answer: (d) Testis
Question 13. The beginning of menstruation at puberty is called
(a) ovulation (b) menstruation (c) menarche (d) menopause
Answer: (c) menarche
Question 14. In males, the sex chromosome consists
(a) one X and one Y (b) both X and X (c) both Y and Y (d) one M and one X
Answer: (a) one X and one Y
Question 15. Production of thyroxin requires
(a) sodium (b) magnesium (c) iodine (d) bromine
Answer: (c) iodine
Question 16. The period of life, when the body undergoes changes, leading to reproductive maturity, is called
(a) childhood (b) adolescence (c) Grown up (d) Old age
Answer: (b) adolescence
Question 17. The human body undergoes several changes during adolescence. These changes mark the onset of
(a) Puberty (b) Prematurity (c) Post adolescence (d) ageing
Answer: (a) Puberty
Question 18. Adam’s apple is prominent in
(a) Boys of any age (b) Adolescent girls (c) Girls of any age (d) Adolescent boys
Answer: (d) Adolescent boys
Question 19. Larynx is also called
(a) Voice box (b) Sound box (c) Black box (d) All of the above
Answer: (a) Voice box
Question 20. Acne and pimples on the face is due to secretion of
(a) bile from liver (b) Oil glands during puberty (c) Enzymes in the digestive tract (d) Tear from tear glands
Answer: (b) Oil glands during puberty
Question 21. Testosterone is a hormone found in human ___
(a) Children (b) males and females (c) Females only (d) Males only
Answer: (d) Males only
Question 22. The first menstrual flow is called
(a) Menstruation (b) Mensuration (c) Menarche (d) Menopause
Answer: (c) Menarche
Question 23. Menopause occurs at the age of
(a) 10-12 years in boys (b) 45-50 years in men (c) 10-12 years in girls (d) 45-50 years in women
Answer: (d) 45-50 years in women
Question 24. When a sperm containing Y chromosome fertilizes an egg with X chromosome, the zygote develops into a _____ child
(a) Female (b) Either a male or female (c) Male (d) No child
Answer: (c) Male
Question 25. The change from larvae to adult is called
(a) Metabolism (b) Metamorphosis (c) Metastasis (d) Morphology
Answer: (b) Metamorphosis
Question 26. Which of the following should an adolescent choose for his/her meal?
(a) Chips, noodles and aerated beverages (b) Vegetable cutlets, chips and lemonade (c) Rice, noodles and popcorn (d) Chapathi, dal and vegetables
Answer: (d) Chapathi, dal and vegetables
Question 27. The reproductive phase of a woman lies between her _____ and menopause.
(a) menstrual cycle (b) menstruation (c) menarche (d) ovulation
Question 28. Number of sex chromosomes in a human kidney cell is
(a) One pair (b) Two pairs (c) Three pairs (d) Four pairs
Answer: (a) One pair
Question 29. A female gamete carries ________ chromosome(s).
(a) one Y (b) one X and one Y (c) two X (d) one X
Answer: (a) one X
Question 30. HIV virus will not be present in which of the following?
(a) Blood (b) Sweat (c) Breast milk (d) Semen
Answer: (b) Sweat
Question 31. Puberty in females begins at the age of _____.
(a) 11 to 13 years (b) 16 to 18 years (c) 14 to 16 years (d) 18 to 21 years
Answer: (a) 11 to 13 years
Question 32. During menstrual bleeding, the fluid that comes out of the vagina contains _____ along with blood.
(a) Embryo (b) ovum (c) sperm (d) zygote
Answer: (b) ovum
Question 33. The time period when the body undergoes changes, leading to reproductive maturity is called______.
(a) Growth (b) senescence (c) development (d) adolescence
Answer: (c) adolescence
Question 34. Which of the following viruses causes AIDS?
(a) H1N1 virus (b) Zika virus (c) HIV (d) Rhinovirus
Answer: (c) HIV
Question 35. In girls, the ovaries and eggs become mature and ovaries begin to release ovum by the process of ______.
(a) Ovulation (b) fertilisation (c) oogamy (d) oogenesis
Answer: (a) Ovulation
Question 36. Which among the following is the change seen in girls during puberty?
(a) Broader shoulders (b) Cracking of voice (c) Breast development (d) Growth of facial hair
Answer: (c) Breast development
Question 37. A human gamete has ________ sex chromosome(s).
(a) Four (b) Half (c) Two (d) One
Answer: (d) One
Question 38. The pituitary gland is located below the ______.
(a) Thalamus (b) medulla oblongata (c) vas deferens (d) hypothalamus
Answer: (d) hypothalamus
Question 39. Which of the following can spread AIDS?
(a) Eating food with an infected person (b) Hugging an infected person (c) Transfusion of infected blood (d) Mosquito bites
Answer: (c) Transfusion of infected blood
Question 40. Deficiency of iodine in our diet leads to a condition called:
(a) Diabetes insipidus (b) Goitre (c) Gigantism (d) Infertility
Answer: (b) Goitre
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Chapter 10 of Class 8 Science discusses the role that hormones play in bringing about changes that make a child grow into an adult. To understand the concepts well and score good marks in the board exams, students can try solving the CBSE Class 8 Science Chapter 10 Reaching the Age of Adolescence Objective Questions.
These questions help the students to face exams more fearlessly because the modified exam papers are expected to include more objective questions or Multiple choice questions.
In this article, students can find a complete list of topics that are covered in the CBSE Class 8 Science objective questions.
10.1 Adolescence and Puberty
10.2 Changes at Puberty
10.3 Secondary Sexual Characters
10.4 Role of Hormones In Initiating Reproductive Function
10.5 Reproductive Phase of Life in Humans
10.6 How is the Sex of the Baby Determined?
10.7 Hormones other than Sex-Hormones
10.8 Role of Hormones in Completing the Life History of Insects and Frogs
10.9 Reproductive Health
Reaching the age of adolescence.
1. Which of the following should an adolescent choose for his/her meal?
A. Chips, noodles and aerated beverages
B. Vegetable cutlets, chips and lemonade
C. Rice, noodles and popcorn
D. Chapathi, dal and vegetables
Answer: (D) Chapathi, dal and vegetables
Solution: Adolescents, like everyone else, should have a balanced diet, which should include
all types of nutrients. Also, the diet should consist of less refined and packaged food. Hence, the best option for an adolescent’s meal will be chapati, dal and vegetables.
2. The reproductive phase of a woman lies between her _____ and menopause.
A. menstrual cycle
B. menstruation
C. menarche
D. ovulation
Answer: (C) menarche
Solution: The reproductive phase of a woman starts from her first period (menarche) at around 10-12 years of age. It continues until the age of 45 to 50, when women stop releasing eggs. This is called menopause. Hence, the reproductive phase of women lies between their menarche and menopause.
3. Statement 1: Sweat glands, salivary glands and oil glands do not release their secretions directly into the blood. Statement 2: These glands do not have ducts.
A. Both statements are correct.
B. Only statement 2 is correct.
C. Both statements are incorrect.
D. Only statement 1 is correct.
Answer: (D) Only statement 1 is correct.
Solution: Endocrine glands release their secretions directly into the blood as they are ductless glands, whereas the exocrine glands like salivary glands have ducts and do not release their secretion into the blood directly.
4. Number of sex chromosomes in a human kidney cell is
A. One pair
B. Two pairs
C. Three pairs
D. Four pairs
Answer: (A) One pair
Solution: Humans have 46 chromosomes, i.e., 23 pairs of chromosomes in all cells except for the gametic cells (sperm and ova). 22 of these pairs are called autosomes and look the same in both males and females. The 23rd pair called sex chromosomes, differ in males and females. Females have two copies of the X chromosome (XX), while males have one X and one Y chromosome (XY). Thus all non-gametic cells have 2 sex chromosomes in them.
5. A female gamete carries ________ chromosome(s).
B. one X and one Y
Answer: (D) one X
Solution: Ovum, which is the female gamete, always carries an X chromosome. This is because the allosome pair in females consists of two X chromosomes (XX).
6. Which of the following is the cause of the condition shown below
A. Lack of calcium in the bones
B. Excess of iron in the blood
C. Lack of iodine in the diet
D. Lack of potassium in the diet
Answer: (C) Lack of iodine in the diet
The picture shows a condition goitre which is caused due to the deficiency of iodine in our diet. It is seen as a swelling in the neck resulting from an enlarged thyroid gland.
7. Which of the following will occur in females at puberty? (I) Ovulation (II) Enlargement of breasts (III) Broadening of hips
A. I, II and III
B. II and III only
C. I and III only
D. I and II only
Answer: (A) I, II and III
Solution: Lot of changes occur during puberty in both boys and girls. In girls, ovulation, enlargement of breasts and broadening of hips are the major changes.
8. HIV virus will not be present in which of the following?
C. Breast milk
Answer: (B) Sweat
Solution: Blood, semen and breast milk all are the body’s internal fluids. Once the virus enters the body, it starts dividing and spreads all over the body. It is present in internal fluids like blood and gets transmitted to other healthy individuals only through the exchange of these body fluids. HIV does not spread through sweat.
9. Puberty in females begins at the age of _____.
A. 11 to 13 years
B. 16 to 18 years
C. 14 to 16 years
D. 18 to 21 years
Answer: (A) 11 to 13 years
Solution: Puberty is the period during which girls and boys become capable of reproduction. Puberty in girls is most commonly observed when they are about 11 to 13 years old.
10. The information given below refers to which of the following hormone- (i) Glands secreting the hormone are located on top of the kidneys. (ii) Converts glycogen into glucose. (iii) Increases blood pressure.
A. Testosterone
C. Adrenaline
D. Progesterone
Answer: (C) Adrenaline
Solution: Adrenaline is secreted by the adrenal glands which are located on top of the kidneys. This hormone prepares the body to fight or run away during an emergency situation. Its effects involve an increase in heart rate, blood pressure, breathing rate, blood glucose level, etc.
11. During menstrual bleeding, the fluid that comes out of the vagina contains _____, along with blood.
Answer: (B) ovum
Solution: The vaginal fluid shed during menstrual bleeding contains the unfertilized egg and the thickened endometrial lining of the uterus along with blood vessels.
12. The time period when the body undergoes changes, leading to reproductive maturity is called______.
B. senescence
C. development
D. adolescence
Answer: (D) adolescence
Solution: Adolescence is the intermediate growing stage between childhood and adulthood. During adolescence, the body undergoes many physical and psychological changes and attains reproductive maturity. This period varies from person to person.
13. Which of the following viruses causes AIDS?
A. H1N1 virus
B. Zika virus
D. Rhinovirus
Answer: (C) HIV
Solution: AIDS is caused by the Human Immunodeficiency Virus (HIV) virus. HIV passes from an infected person to a normal person through sexual contact, sharing syringes, breastfeeding etc.
14. In girls, the ovaries and eggs become mature and ovaries begin to release ovum by the process of ______.
A. Ovulation
B. fertilisation
D. oogenesis
Answer: (A) Ovulation
Solution: Ovulation is the process in which mature ovaries release egg cell or the ovum. Usually, a single egg is produced during an ovulation cycle. The female hormone, oestrogen is released by the ovaries which promote ovulation.
15. Which among the following is the change seen in girls during puberty?
A. Broader shoulders
B. Cracking of voice
C. Breast development
D. Growth of facial hair
Answer: (C) Breast development
Solution: One of the major changes in girls during puberty is breast development. Also, in girls, the region below the waist becomes wider during puberty, while in boys, the chest becomes wider and the shoulders become broad.
16. A human gamete has ________ sex chromosome(s).
Answer: (D) One
Solution: A human cell has 46 chromosomes in total. Out of these 46 chromosomes, 44 are autosomes and 2 are sex chromosomes. Chromosomes occur in pairs and thus there are 23 pairs. A cell having 23 pairs of chromosomes is called diploid. Diploid cells undergo division and their number reduces to half, i.e. produce haploid cells having only 23
chromosomes, without any pairs. These cells are also called gametes. Thus, gametes have only one sex chromosome.
17. The pituitary gland is located below the ______.
A. Thalamus
B. medulla oblongata
C. vas deferens
D. hypothalamus
Answer: (D) hypothalamus
Solution: The pituitary gland is a pea-sized gland located just below the hypothalamus which is connected to the pituitary via a bundle of nerve fibres. It is known as the master gland of the endocrine system as it produces all the critical hormones which regulate the secretions of all other endocrine glands.
18. What happens during menopause? A. No menstruation. B. No maturation of new follicles. C. The ovaries stop the secretion of oestrogen
B. A, B and C
Answer: (B) A, B and C
Solution: Menopause is the time in all women’s lives when the menstrual cycle stops permanently. It typically occurs between 49 and 52 years of age. At menopause, no oestrogen is secreted by the ovaries and thus, no new follicles and hence, no ovulation occurs; therefore, menstruation stops.
19. Which of the following can spread AIDS?
A. Eating food with an infected person
B. Hugging an infected person
C. Transfusion of infected blood
D. Mosquito bites
Answer: (C) Transfusion of infected blood
Solution: AIDS is caused by the HIV virus. It can spread through various means, like i. Sexual contact with an infected person. ii. Transfusion of contaminated blood. iii. From a pregnant mother to her child during birth or breastfeeding. It does not spread by: i. Touching, kissing and socialising with the infected person. ii. Eating meals with an infected person. iii. Mosquito bites.
20. Deficiency of iodine in our diet leads to a condition called:
A. Diabetes insipidus
C. Gigantism
D. Infertility
Answer: (B) Goitre
Solution: Iodine is essential for the production of thyroxine. In an attempt to produce more thyroxine, the gland enlarges. This condition is called goitre.
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In this page, we are providing Reaching the Age of Adolescence Class 8 Extra Questions and Answers Science Chapter 10 pdf download. NCERT Extra Questions for Class 8 Science Chapter 10 Reaching the Age of Adolescence will help to score more marks in your CBSE Board Exams.
Extra Questions for Class 8 Science Chapter 10 Reaching the Age of Adolescence with Answers Solutions
Question 1. What is Adam’s apple? Answer: The protruding part of the throat in males is called Adam’s apple.
Question 2. Name the hormone in female that is produced by ovaries and helps in development of mammary glands. Answer: Estrogen
Question 3. Whose height grow faster initially boys or girls? Answer: Girls
Question 4. Name a gland which transports secretions through ducts. Answer: Sweat glands/salivary glands/ oil gland (any one).
Question 5. What is puberty? Answer: The age at which boys and girls become capable of reproduction.
Question 6. What are hormones? Answer: The chemical substances produced by endocrine glands are called hormones.
Question 7. How long is a woman’s reproductive life lasts? Answer: Menarche to menopause.
Question 8. Name the female hormone. Answer: Estrogen
Question 9. Which gland is called master gland? Answer: Pituitary gland
Question 10. What is a balanced diet? Answer: The meal that includes all nutrients is called a balanced diet.
Question 11. What is menstruation? Answer: Extrusion of uterus lining and blood along with the unfertilised egg from the vagina is called menstruation.
Question 12. What is menarche? Answer: The first menstrual flow begins at puberty and is termed as menarche.
Question 13. What is menopause? Answer: Stoppage of menstruation is called menopause.
Question 14. What causes goitre? Answer: Deficiency of thyroxine hormone.
Question 15. Which gland secretes thyroxine? Answer: Thyroid gland
Question 16. What are chromosomes? Answer: The thread-like structures in the nucleus are called chromosomes.
Question 17. How many chromosomes are present in human cell? Answer: 23 pairs or 46 chromosomes.
Question 18. How many sex chromosomes are there in human cell? Answer: Two, i.e., one pair.
Question 19. Which hormone is necessary for normal growth of a person? Answer: Growth hormone.
Question 20. Which gland secretes insulin? Answer: Pancreas
Question 21. What causes diabetes? Answer: Deficiency of insulin.
Question 22. Name the chromosome present in a female. Answer: X chromosome
Question 23. Name the chromosome present in a male. Answer: X and Y chromosomes
Question 24. Which chromosome does the unfertilised egg contain? Answer: X chromosome
Question 25. Which hormone balances the proportion of salts in the blood? Answer: Adrenaline
Question 26. What decides the sex of an unborn child? Answer: Sex chromosome of father.
Question 27. Name the glands other than the pituitary gland. Answer: Thyroid, pancreas and adrenals.
Question 28. When does the puberty ends? Answer: Puberty ends when an adolescent reaches reproductive maturity.
Question 29. Do the boys and girls undergo same physical changes at puberty? Answer: No
Question 30. Why do we need to have a balanced diet? Answer: To keep the body healthy.
Question 1. What is meant by adolescence? Answer: Growing up is a natural process. The period of life, when the body undergoes several changes leading to reproductive maturity, is cabled adolescence. The adolescence period is 11 to 19 years of age.
Question 2. What is puberty? Answer: The period during which adolescent boys and girls attain sexual maturity and become capable of reproduction is called puberty. Puberty age of female is 10 to 12 years while male puberty age is 12 to 14 years.
Question 3. What is vital change which marks puberty in boys and girls? Answer: During puberty, the human body undergoes several changes, but the most important changes which marks puberty is that boys and girls become capable of reproduction.
Question 4. Why do boys have a hoarse voice at puberty? Answer: The voice box or larynx begins to grow at the onset of puberty. This growing voice box in boys can be seen as a protruding part of the throat called Adam’s apple. This leads to voice becoming hoarse.
Question 5. How does the body shape change at puberty? Answer: Body shape changes differently in boys and girls at puberty. Boys have broader shoulders and wider chests. Their muscles grow more prominently than girls. In girls, the region below the waist becomes wider.
Question 6. Why is adolescence also called teenage? Answer: Adolescence period is generally 11 to 19 years of age. Because the period covers the teens, i.e., 13 to 19 years of age, adolescents are also called teenagers.
Question 7. Why do many young people have acne and pimples during adolescence? Answer: During puberty the secretion of sweat glands and sebaceous glands (oil glands) increases. It develops acne and pimples on the face of young boys and girls.
Question 8. Why are endocrine glands also called ductless glands? Answer: Endocrine glands release hormones directly into the blood stream. So, they are termed as ductless glands. For example, pituitary, thyroid, pancreas, etc.
Question 9. What are secondary sexual characters? Answer: At puberty, in girls, breasts begin to develop, the region below the waist become wider, voice become shriller. Boys begin to grow facial hair, i.e., moustache and beard. Boys also develop hair on their chest, the muscles of the body grow more prominently, develop larger voice box which can be seen as a protruding part of the throat called Adam’s apple. In both boys and girls, hair grows under the arms and in the pubic region. As these features distinguish the male from the female they are called secondary sexual characters.
Question 10. Explain the development of sex organs in male and female. Answer: The male and the female sex organs develop completely at puberty. Male sex organ like testes and penis develop completely. The testes begin to produce the male gametes or sperm. Similarly in girls the ovaries enlarge and egg begins to mature. Ovaries start releasing matured eggs or ovum.
Question 11. Why do changes occur in human body at puberty? Answer: The changes in human body at puberty occur due to release of hormones by different types of glands. Hormones are chemical substances secreted from endocrine glands or endocrine system. Male hormone or testosterone are responsible for changes in male whereas female hormone or estrogen are responsible for changes in female.
Question 12. What is a pituitary gland? Answer: Different types of hormones are secreted by different types of glands. The product of all these hormones is under the control of another hormone secreted from an endocrine gland called pituitary gland.
Question 13. How do hormones work in human body? Answer: Endocrine glands release hormones into the blood stream to reach a particular body part called target site. The target responds to the hormone. There are many endocrine glands or ductless glands in the body.
Question 14. What are sex hormones? How do they work in the human body? Answer: Sex hormones help boys and girls develop sex organs to enable them for reproduction. These hormones lead them to reproductive maturity.
In girls, estrogen makes the breasts develop. Milk secreting glands or mammary glands develop inside the breasts. Ovaries begin to produce eggs. In boys, testosterone is released by testes. Testes begin to release sperms. Changes in boys is also seen due to this hormone.
Question 15. What is menstruation? Answer: At puberty, in girls the ovaries get enlarged and start producing eggs (ovum). One egg matures and is released by one of the ovaries once in about 28 to 30 days. During this period, the wall of the uterus becomes thick so as to receive the egg. If the egg is fertilised then it begins to develop and results in pregnancy. If this egg is not fertilised, the released egg and thickened lining of the uterus along with its blood vessels are shed off causing bleeding in female which is called menstruation. It occurs once in about 28 to 30 days.
Question 16. What are the changes in female at the onset of puberty? Answer: There are several changes in females at the onset of puberty. They are:
Question 17. Explain the terms menarche and menopause. Answer: The first menstrual flow begins at puberty and is termed as menarche. At 45 to 50 years of age, the menstrual cycle stops. Stoppage of menstruation is called menopause.
Question 18. What happens when the egg is fertilised? Answer: When the egg is fertilised, it begins to divide and then gets embedded in the uterus for further development. Finally the fertilised egg develops into a foetus.
Question 19. What are the changes in males at puberty? Answer: There are various changes in males at puberty. They are:
Question 20. What do you mean by reproductive health? Answer: The physical and mental well being of an individual is regarded as an individual’s health. To keep the body healthy, every human being, at any age, needs to have a balanced diet. The person must also observe personal hygiene and undertake adequate physical exercise. Thus, reproductive health refers to the diseases, disorders and conditions that affect the functioning of the male and female reproductive system during all stages of life.
Question 21. What is the role of hormones in completing the life history of insects and frogs? Answer: Hormones play an important role in the completion of life cycle of insects and frogs. Metamorphosis in insects is controlled by insect hormones. In a frog, it is controlled by thyroxine, the hormone produced by thyroid gland. Thyroxine production requires the presence of iodine in water. Water in which iodine is not, present, the tadpoles cannot become adult.
Question 22. Which hormone is released by pancreas? What is its function? Answer: Insulin is released by pancreatic gland. It regulates sugar metabolism. If insulin is deficient in the body, sugar level becomes high in blood causing diabetes.
Question 1. What changes occur in human at puberty? Answer: There are various changes in human at puberty. They are as follows: (i) Change in height: During puberty, there is sudden increase in height in boys and girls. Initially, girls grow faster in height than in boys. But both reach their maximum height at the age of 18 years.
(ii) Change in voice: Boys develop larger voice box or larynx to form protruding part of throat called Adam’s apple making their voice hoarse, girls have high pitched voice.
(iii) Change in body shape: In boys, shoulders broaden and muscles grow more prominently than in girls. In girls the region below the waist becomes wider.
(iv) Secretion of sweat and sebaceous glands (oil glands) in both boys and girls increases and acne or pimples grow on faces of many youths.
(v) Development of sex organs: In males, testes and penis develop completely. Testes begin producing sperms. In girls, ovaries are enlarged and begin to produce eggs. Both boys and girls reach reproductive maturity.
(vi) In girls, menstruation or periods starts.
(vii) All human beings attain mental, intellectual and emotional maturity at puberty.
(viii) Facial hair like moustache and beard are grown in boys. Hair are grown in armpit and pubic region in both boys and girls. Breasts are developed in girls. These characters are called secondary sexual characters as they distinguish a male from a female.
Question 2. Explain the reproductive phase of life in humans. Answer: Boys and girls become capable of reproduction at puberty because their testes and ovaries begin to release gametes, i.e., sperms and ova respectively. In girls, reproductive phase of life begins at puberty from 10 to 12 years of age and generally lasts till the age of 45 to 50 years. The ova begin to mature with the onset of puberty. The ovum matures and is released by one of the ovaries once in 28 to 30 days. During this period, the wall of the uterus becomes thick so as to receive the egg, in case it is fertilised and begins to develop. This results in pregnancy.
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 menstruation. It occurs once in about 28 to 30 days. The first menstrual flow begin at puberty and is termed as menarche. The menstruation stops at the age of 45 to 50. This stage is known as menopause. In male, the reproductive phase begins at puberty at the ages 14-15 and lasts as long as he is healthy.
Question 3. Mention different types of glands, their functions and hormones secreted by them. Answer: There are different types of glands in our body and they secrete different types of hormones which control grotto, behaviour, development and reproduction. The following table shows different types of glands, hormones secreted by them and their functions:
1. | Pituitary | Several hormones including growth hormone, thyroid stimulating hormones, etc. | (i) Produces thyroxine hormone and stimulate thyroid gland. (ii) Controls growth. (iii) Keeps a check on the activity of other glands. |
2. | drenal | Adrenaline | (i) Regulates blood pressure, breathing rate, heart beat, etc. (ii) Helps the body to adjust the stress condition. |
3. | Thyroid | Thyroxine | (i) Helps in controlling growth, respiration and metabolism. (ii) Prevents from goitre disease. |
4. | Testes | Male hormone or testosterone | Develops secondary sexual characters and control releasing of sperms. |
5. | Ovaries | Female hormone or estrogen | Develop secondary sexual character, maturation and release of ovum and helps in maintaining the growth of uterus during pregnancy. |
6. | Pancreas | Insulin | Controls sugar level and prevents from diabetes. |
Question 4. Explain sex determination in human. Answer: Sex determination of a baby is done at the time of fertilisation when a male gametes fuse with a female gamete. It depends on male partner whether the baby will be a male child or female child. The chances of child to be male or female actually depend on the chromsomes present in the fertilised eggs or ova. There are 23 pairs of chromosomes in the nuclei of all human beings out of which two are sex chromosomes named X and Y.
A male has one X and one Y chromosome and a female has two X chromosomes. The gametes (egg and sperm) have only one set of chromosomes. The unfetilised 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 fertilisation, the zygote would develop into a male child. Fig. 10.5 shows sex determination in humans.
Question 5. Explain the term reproductive health. What should we do to maintain reproductive health? Answer: The state of physical, mental and social well being of an individual is regarded as an individual’s health. A healthy person is free from disease, tension and anxiety. Reproductive health refers to a state of physical, mental and social well-being in all matters relating to the reproductive system, at all stages of life.
We should take following measures to maintain reproductive health:
Question 1. One day Seema’s uncle visited her place. Seema prepared dinner for him. When she was about to put rock salt on the salad, her uncle interrupted her and asked to put iodised salt instead of rock salt. He also advised her to prefer iodised salt instead of rock salt. Why do you think Seema’s uncle advised her to have iodised salt instead of rock salt? Answer: Deficiency of iodine causes goitre disease in our body. This is why Seema’s uncle advised her to have iodised salt.
Question 2. It is said that height of a child depends upon the genes inherited from the parents. Are there factors other than genes that causes variation in height? Answer: Other factors like nutrition, release of growth hormones, exercises, diseases, etc., also have impact on the height of a growing child.
Question 3. Is a woman responsible for the birth of a girl child? Explain. Answer: No, because a woman has eggs of only X chromosomes but a male has sperms of both X and Y chromosomes. It is the type of male chromosome (X or Y) which fuses with the egg and determine the sex of the foetus, i.e., whether it will be male (XY) or female (XX) child.
Question 4. 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? Answer: The swelling on the neck of Radha may be because of insufficient production of thyroxine which results in goitre. However slight protrusion in John’s throat may be due to enlargement of voice box, also known as Adam’s apple, in adolescent boys.
Question 5. Why we should not take medicines or drugs unless prescribed by a doctor? Answer: Certain medicines have specific dosage levels and adverse side effects which if not followed may be proved lethal to us. Drugs can be addictive too and can ruin our health and happiness.
Question 1. Salma had a very soft and smooth skin during her childhood. As she entered adolescence, she developed pimples on her face, her body became taller compared to her face. She got worried of all of the sudden changes. Her mother explained that all these changes are normal and advised her to wash her face at regular intervals.
(a) Why Salma’s mother advised Salma to wash her face at regular intervals? (b) What is the reason for appearance of pimples on her face? (c) Why Salma experienced disproportionate growth of the body? (d) What values do we get from this? Answer: (a) Regular face wash keeps the face clean and dry and helps to reduce the pimples. (b) During adolescence, secretion of sweat glands and sebaceous glands increases leading to formation of acne and pimples. (c) During adolescence, all parts of the body do not grow at the same rate. Sometimes the arms and legs or hands and feet of adolescents look oversized and out of proportion with the body. (d) We must be self-aware, must take proper care and diet during the growing period, not get worried or lose our self-esteem.
COMMENTS
Que. 1) (c) Adam's apple. Que. 2) (d) Region below waist wider. Que. 3) (a) Ovaries. Que. 4) Answer: In males, sex organs like testes and penis develop completely at puberty. The testes begin to produce sperms. Que. 5) Answer: During puberty the secretion of sweat glands and sebaceous glands (oil glands) increases.
Case Study Questions for Class 8 Science Chapter 10 Reaching the Age of Adolescence Here we are providing case study questions for CBSE Class 8 Science Chapter 10 Reaching the Age of Adolescence. Case Study Questions Question 1: Read the given passage and answer the following questions. The changes which occur during adolescence in the … Continue reading Case Study Questions for Class 8 ...
NCERT Exemplar Solutions Class 8 Science Chapter 10 - Free PDF Download. NCERT Exemplar Solutions for Class 8 Science Chapter 10 Reaching the Age of Adolescence aid you in gaining in-depth knowledge of the topic included in the CBSE Class 8 syllabus. By practising these NCERT Exemplar Solutions, you will be able to get a stronghold on the basic topics and will be able to answer the questions ...
Reaching the Age of Adolescence Class 8 Science NCERT Intext Activities Solved. Activity 1 (NCERT Textbook, Page 114) The following chart gives the average rate of growth in height of boys and girls with age. The figures in columns 2 and 3, give the percentage of the height a person has reached at the age given in column 1.
Quick Insights for NCERT Solutions for Class 8 Chapter 7 Science. Class 8, Reaching the Age of Adolescence, offers a comprehensive understanding of the physical and emotional changes accompanying puberty. Reaching the Age of Adolescence Class 8 PDF delves into the details of puberty, explaining the biological processes that trigger the onset of ...
Solutions of Chapter 7 Reaching the Age of Adolescence NCERT Science Class 8. Meticulously crafted NCERT solutions to boost your CBSE board exam preparation. Easily score more marks in Science CBSE exam.
Courses. Study Important Questions for Class 8 Science Chapter 10 - Reaching Age of Adolescence. Very Short Answer Questions: 1 Marks. 1. The period of maturity of reproductive organs is called ___________. A. adolescence period B. menstruation. C. gestation period D. none of these. Ans: A. adolescence period.
Teachoo provides Notes, NCERT Solutions, Worksheets of Chapter 10 Class 8 - Reaching The Age Of Adolescence. In this chapter, we will learn. What is the meaning of Adolescence and Puberty. Different changes during Puberty. What are Primary and Secondary Sexual Characteristics?. What is the meaning of Menstruation, Menopause and Menarche. Comparison between Reproductive Phases of Males and Females
Case Study Questions on Reaching the Age of Adolescence. Questions. Question 1: Read the given passage below and answer the question: The most conspicuous change during puberty is the sudden increase in height. At this time the long bones, that is, the bones of the arms and the legs elongate and make a person tall.
Chapter 10 Reaching the Age of Adolescence NCERT Solutions for Class 8 Science - Notes. • 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 human body undergoes several changes during adolescence.
Question 2: Define adolescence. Answer: Adolescence is the time period between the beginning of puberty and adulthood. During this period, the body undergoes several changes alongside reproductive maturity. It begins around the age of 11 and lasts till 18 or 19 years of age. The period of adolescence may vary from person to person.
Answer. → The various changes that occur in the body during adolescence marks the onset of puberty. → Puberty ends when teenagers attain sexual maturity. → Changes that take place during puberty. Increase in height. → It is caused by the growth in long bones of the arms and legs. → Girls grow faster than boys initially but both reach ...
NCERT Exemplar Class 8 Science Chapter 10 Reaching the Age of Adolescence. Question. 1 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 ...
Here you can get Class 8 Important Questions Science based on NCERT Text book for Class 8. Science Class 8 Important Questions are very helpful to score high marks in board exams. Here we have covered Important Questions on Reaching the Age of Adolescence for Class 8 Science subject. Very Short Answer Questions. 1.
In both boys and girls, hair grows under the arms and in the pubic region. As these features distinguish the male from the female they are called secondary sexual characters. Question 10. Explain the development of sex organs in male and female. Answer: The male and the female sex organs develop completely at puberty.
NCERT Solutions for Class 8 Science Chapter 10 - Free PDF Download *According to the CBSE Syllabus 2023-24, this chapter has been renumbered as Chapter 6. NCERT Solutions for Class 8 Science Chapter 10 Reaching the Age of Adolescence, is the best study material for those students who are having difficulties in preparing for their exams. The NCERT Solutions contain answers to all the ...
Question 8: List changes in the body that take place at puberty. Or. State some of the changes which take place in boys and girls during adolescence. Answer: Changes at puberty. Sudden increase in height and weight. Boys develop broader shoulders and wider chests. In girls, the region below the waist becomes wider.
Adolescence. The period of life, when the body undergoes changes, leading to reproductive maturity, is called adolescence. This is the time span in which the child develops into an adult. Adolescence begins around the age of 11 and goes on until 18 or 19 years of age. Adolescents are also called 'teenagers'.
Click on the three lines on the upper left side, and then tap on the 'CBSE' Option, scroll down and click on the option stating 'MCQ Tests'. A page will appear in which there will be options for choosing classes. Choose class 8. Now, you have to choose the subject and the chapter. Now, you can attempt Reaching the Age of Adolescence ...
Reaching the Age of Adolescence Class 8 MCQ with Answers. Multiple Choice Questions (MCQs) Question 1. Adolescence is the period of. Answer: (b) 11 to 19 years. Question 2. When a sperm having X-chromosome fuses with the ovum, the child born will be. Answer: (b) female. Question 3.
By solving these important questions of Class 8 Science Chapter 10 students can analyze their performance and get to know whether they have skipped any important topic from the chapter. Download these important questions for Class 8 Science Chapter 10 - Reaching the Age of Adolescence PDF and kickstart your preparation by solving it.
Chapter 10 of Class 8 Science discusses the role that hormones play in bringing about changes that make a child grow into an adult. To understand the concepts well and score good marks in the board exams, students can try solving the CBSE Class 8 Science Chapter 10 Reaching the Age of Adolescence Objective Questions.
In both boys and girls, hair grows under the arms and in the pubic region. As these features distinguish the male from the female they are called secondary sexual characters. Question 10. Explain the development of sex organs in male and female. Answer: The male and the female sex organs develop completely at puberty.