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Q1. Why is adolescent marriage and pregnancy not legally allowed?

Solution

Adolescent marriage and pregnancy is not legally allowed due to the following reasons: (i) Early marriage and motherhood cause health problems in the mother and the child. (ii) Teenage mothers are not prepared mentally or physically for motherhood. (iii) Early marriage and motherhood also curtails employment opportunities for the young woman and may cause mental agony as she is not ready for responsibilities of motherhood

Q2. Height of a person depends both on genes as well as nourishment. Explain.

Solution

Height mainly depends on the genes inherited from parents. It is, however, very important to eat the right kind of food during the growing years. This helps the bones, muscles and other parts of the body get adequate nourishment for growth.

Q3. What changes occur in the sex organs of girls and boys during puberty?

Solution

At puberty, male sex organs like the testes and penis develop completely. The testes also begin to produce sperms. In girls, the ovaries enlarge and eggs begin to mature so the ovaries start releasing mature eggs.

Q4. Answer the following: (i) Thread like structures present in the nucleus and carrying genetic information.(ii) Number of chromosomes in every human.(iii) Number of chromosomes in gametes.(iv) Number of sex chromosomes.(v) The sex chromosomes in male.(vi) The sex chromosomes in female.

Solution

(i) Chromosomes(ii) 46(iii) 23(iv) 2(v) XY(vi) XX

Q5. Give reasons:(i) Adolescents are also called teenagers.(ii) During puberty, there is sudden increase in height.(iii) In some adolescent boys, the voice become hoarse.

Solution

(i) The period of adolescence covers the 'teens' i.e. 13 to 18 or 19 years of age. Hence adolescents are also called teenagers.(ii) During puberty, the long bones i.e. the bones of the arms and the legs elongate and make a person tall. This results in sudden increase in height.(iii) Sometimes in adolescent boys, the muscles of the growing voice box go out of control and the voice becomes hoarse.

Q6. When does the reproductive phase of life begin and end in:(i) Females(ii) Males

Solution

(i) In females, the reproductive phase of life begins at puberty i.e. 10 to 12 years of age, and generally lasts till the age of approximately 45 to 50 years.(ii) In males the reproductive phase is from the age of 13 to life long.

Q7. What do you understand by adolescence? When does it take place?

Solution

The period of life, when the body undergoes changes, leading to reproductive maturity, is called adolescence. Adolescence begins around the age of eleven and lasts upto 18 or 19 years of age.

Q8. What is metamorphosis?

Solution

The transformation of the larva into an adult through drastic changes is called metamorphosis.

Q9. Name the male sex hormone.

Solution

Testosterone is the male sex hormone secreted by testis.

Q10. What are the different stages of life based on the age of an individual?

Solution

Life stages:

Infant - Children between 1 month and 1 year of age

Toddler - Children between the ages of 1 and 4 years

Adolescent - Children between the ages of 11 and 19 years

Adulthood - Begins from the age of 18 years onwards 

Q11. Why does the diet of adolescents need:(a) Iodine(b) Calcium(c) Iron

Solution

(a) Iodine helps to prevent thyroid gland related diseases. (b) Due to an increase in skeletal mass, the adolescent diet should include calcium. Calcium intake needs to be increased to prevent osteoporosis in later life. (c) To compensate for iron deficiency due to muscle spurt in boys and menstruation as well as muscle spurt in girls, the diet of adolescents need iron rich diet. Lack of iron in the diet results in anemia.

Q12. Which sex organs are present in females since birth?

Solution

Ovaries

Oviducts

Uterus

Vagina 

Q13. Name one hormone secreted by: (a) Adrenal gland (b) Pituitary gland (c) Pancreas (d) Thyroid gland

Solution

(a) Adrenaline(b) Growth hormone(c) Insulin(d) Thyroxine

Q14. Why should the diet of an adolescent need to be carefully planned?

Solution

Adolescence is a stage of rapid growth and development. Hence the diet for an adolescent has to be carefully planned

Q15. What do you understand by the terms menarche and menopause.

Solution

The first menstrual flow which begins at puberty is termed menarche. Stoppage of menstruation at about 45 to 50 years of age is termed menopause.

Q16. Write any two ways how the HIV virus can be transmitted from an infected person to a healthy person.

Solution

(i)  HIV virus can pass on to a normal person from an infected person by sharing the syringes used for injecting drugs. (ii) It can also be transmitted to an infant from the infected mother through her milk. (iii) Another way of transmission is through sexual contact with a person infected with HIV. (Any 2)

Q17. Name the gland which is responsible for the secretion of calcitonin and state its function.

Solution

Calcitonin is secreted by the thyroid gland, and it regulates the levels of calcium and phosphate in the blood.

Q18. What is adolescence?

Solution

The period of life of a person when the body undergoes a lot of changes leading to reproductive maturity is called adolescence. 

Q19. What do you understand by the following:(a) Adam's apple(b) Hormones(c) Puberty

Solution

(a) The growing voice box in boys seen as a protruding part of the throat is called Adam's apple.(b) Hormones are chemical substances secreted by endocrine glands.(c) The period during which adolescents reach sexual maturity and become capable of reproduction.

Q20. Which food products (any 2 of each) are rich in:(a) Proteins(b) Iron

Solution

(a) Milk, meat, nuts and pulses(b) Green leafy vegetables, jaggery, whole pulses (Any 2 of each)

Q21. List the functions of sex hormones.

Solution

Regulate spermatogenesis or oogenesis

Regulate the structural development, maintenance and functions of accessory sex organs

Help to develop secondary sexual characters at the proper age 

Responsible for changes in the face, body structure and appearance; development of mammary glands; pitch of the voice; vigilant behaviour and sentimental behaviour

Q22. Only the father is responsible for determining the sex of the child. Explain with the help of an illustration.

Solution

The father (male parent) produces X- and Y-bearing gametes or sperms, whereas the mother (female parent) produces only X-bearing gametes or eggs. During reproduction, the combination of the X-bearing gamete from the male with one X-bearing gamete from the female results in offspring with genetic constitution XX. The child produced is a female or daughter. This proves that only the father is responsible for determining the sex of the child.    

Q23. How are acne and pimples caused?

Solution

With the onset of puberty, there is an increase in the secretion of oil and sweat glands. When there is excessive secretion of these body fluids, the oil and sweat along with cellular debris collect in the glands. The growth of bacteria in these blocked pores results in the formation of acne and pimples.

Q24. State the disease caused by the deficiency of

Growth hormone

Thyroxine 

Insulin 

Solution

Deficiency diseases:

Growth hormone - Dwarfism

Thyroxine - Goitre

Insulin - Diabetes 

Q25. Discuss the intellectual, mental and emotional development occurring in adolescents.

Solution

Adolescence is a period of change in a person's way of thinking. Adolescents are more independent than before and are also self conscious. Intellectual development takes place and they tend to spend considerable time on thinking. Often, this is the time in one's life when the brain has the greatest capacity for learning. Some adolescents may feel insecure while trying to adjust to the changes in the body and mind.

Q26. Where are the adrenal glands located? Name the hormone secreted by adrenal glands. Write its two important functions.

Solution

Adrenal glands are located on the top of the kidneys. Adrenaline hormone is secreted by adrenal glands. Functions: (i) Adrenaline hormone maintains the correct salt balance in the blood. (ii) It helps during stress or emergency situations by regulating heart beat, breathing rate, blood pressure etc.

Q27. Why endocrine glands are called ductless glands?

Solution

Endocrine glands release hormones directly into the bloodstream. So, they are also termed ductless glands.

Q28. (a) Write any two changes occurring in body shape of boys during puberty.(b) Acne and pimples are common on the face of girls and boys undergoing puberty. Why?

Solution

(a) (i) During puberty, the shoulders become broader and chest becomes wider.(ii) Their muscles become more prominent during puberty. (b) The secretion of sweat and sebaceous glands increases during puberty. This causes acne and pimples on the face of boys and girls during this time.

Q29. Write any three ways of personal hygiene that needs to be practiced, especially by adolescents.

Solution

i. Shower or bath daily. ii. Always wash your hands before and after meals and keep fingernails clean. iii. Wash your teeth and mouth before and after each meal. iv. Change your clothes, especially undergarments, everyday. v. Girls should take special care of cleanliness during the time of menstrual flow.(Any 4)

Q30. State two changes which take place in boys at puberty.

Solution

Testes mature and start producing sperms

Pectoral girdle (shoulder girdle) grows

Hair growth in the pubic region

Development of moustache and beard

Development of deep voice

(ANY TWO)

Q31. Discuss how the process of menstruation occurs in females.

Solution

Once in about 28 to 30 days, one ovum matures and is released by one of the ovaries. During this period, the wall of the uterus becomes thick so as to receive the egg, in case it is fertilised. If fertilisation does not occur, the released egg, and the thickened lining of the uterus along with its blood vessels are shed off. This causes bleeding in women which is called menstruation.

Q32. (a) Which gland controls the secretion of sex hormones?(b) By which process an ovum is released from an ovary?

Solution

(a) Pituitary gland(b) Ovulation

Q33. List the benefits of exercise during adolescence.

Solution

Benefits of regular exercise:

Keeps the body fit

Improves mental health

Protects the person from heart disease, high blood pressure, diabetes and obesity

Builds and maintains healthy muscles, bones and joints

Increases efficiency in studies, sports and work

Improves the general sense of well-being and makes a person feel happy 

Q34. Diagrammatically explain the events of the menstrual cycle.

Solution

 

Q35. In many parts of India, the mother is blamed for the sex of the child. Justify that this is a wrong assumption.

Solution

The mother has two X chromosomes, while the father has one X and one Y chromosome. The gametes i.e. egg and sperm have only one set of chromosomes. The unfertilised egg always has one X chromosome. But sperms may carry either X chromosome or Y chromosome. When a sperm containing X chromosome fertilises the egg, the zygote would have two X chromosomes (XX) and develop into a female child. But, when a sperm containing Y chromosome fertilizes the egg, the zygote would have one X chromosome and one Y chromosome (XY), and develop into a male child. Thus, the father determines the sex of the child and not the mother.

Q36. Why is it that the government is encouraging the use of iodised salt?

Solution

Iodine is very essential for production of thyroxine hormone by thyroid gland. If iodine is not available in the right amounts to the body, the thyroid gland will be unable to produce the required quantity of thyroxine and will eventually enlarge and form goitre. But iodine is not easily available in our food and hence consuming iodised salt is essential.

Q37. Sanya is confused and insecure about the changes happening in her body during adolescence. Her friends suggest that taking some drugs will help her feel relaxed and secure. Should Sanya take these drugs? Why or why not?

Solution

Sanya should not take any drugs suggested by her friends for the following reasons: (i) Drugs are addictive. On taking them once, you feel like taking them again and again. (ii) Drugs harm the body in the long run. (iii) They ruin health and happiness. Sanya should consult a doctor and then follow the doctor's prescription.

Q38. Write any two ways that girls should take care of themselves during menstruation.

Solution

(i) Girls should take special care of cleanliness during the time of menstrual flow. (ii) They should consume a diet rich in iron to compensate for the iron deficiency occurring during menstruation.

Q39. What will happen if the water in which the tadpoles are growing, lacks sufficient iodine? Give reason for your answer.

Solution

If the water in which the tadpoles are growing lacks sufficient iodine, the tadpoles cannot become adults. This is because in frog, metamorphosis is controlled by thyroxine, the hormone produced by thyroid. For thyroxine production, sufficient amounts of iodine must be present in water.

Q40. In girls, which hormone is produced by ovary during puberty? How does this hormone affect the mammary glands?

Solution

During puberty, ovaries produce the female hormone called estrogen. This hormone makes milk secreting glands called mammary glands, which develop inside the breasts.

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