Case Study Based Questions: Reaching the Age of Adolescence | Science Class 8 PDF Download

Case Study 1

Changes at Puberty: Increase in Height 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. Initially, girls grow faster than boys but by about 18 years of age, both reach their maximum height. The rate of growth in height varies in different individuals. Some may grow suddenly at puberty and then slow down, while others may grow gradually. There is no need for Paheli to worry. All parts of the body do not grow at thesame rate. Sometimes the arms and legs or hands and feet of adolescents look over sized and out of proportion with the body. But soon the other parts catchup and result in a proportionate body. You must have noticed that height of an individual is more or less similar to that of some family member. This is because height depends on the genes inherited from parents. It is, however, very important to eat the right kind of food during these growing years. This helps the bones, muscles and other parts of the body get adequate nourishment for growth. You will find nutritional needs of adolescents discussed later in the lesson. Change in Body Shape: Have you noticed that boys in your class have broader shoulders and wider chests than boys in junior classes? This is because they have entered the age of puberty when shoulders generally broaden as a result of growth. In girls, the region below the waist becomes wider. In boys, the muscles of the body grow more prominently than in the girls. Thus, changes occurring in adolescent boys and girls are different. Voice Change: Did you notice that sometimes the voice of some of the boys in your class cracks? At puberty, the voice box or the larynx begins to grow. Boys develop larger voice boxes. The growing voice box in boys can be seen as a protruding part of the throat called Adam’s apple. In girls, the larynx is hardly visible from the outside because of its small size. Generally, girls have a high-pitched voice, whereas boys have a deep voice. In adolescent boys, sometimes, the muscles of the growing voice box go out of control and the voice becomes hoarse. This state may remain for a few days or weeks after which the voice becomes normal. Increased Activity of Sweat and Sebaceous Glands: During puberty the secretion of sweat glands and sebaceous glands (oil glands)increases. Many young people get acne and pimples on the face at this time because of the increased activity of these glands in the skin. Development of Sex Organs: 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. Also, ovaries start releasing mature eggs. Reaching Mental, Intellectual and Emotional Maturity Adolescence is also 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 thinking. In fact, it is often the time in one’s life when the brain has the greatest capacity for learning. Sometimes, however, an adolescent may feel insecure while trying to adjust to the changes in the body and mind. But as adolescent learners, you should know that there is no reason to feel insecure. These changes are a natural part of growing up.

Q1: The protruding part of the throat usually seen in boys that is responsible for a deep voice is known as?
(a) Goitre
(b) Swollen lymph
(c) Adam’s apple
(d) Thyroid
Ans: (c)

Q2: Which of the following is a change in body shape usually observed in girls?
(a) Broader shoulder
(b) Increased muscle growth
(c) Deep voice
(d) Region below waist wider
Ans: (d)

Q3: During puberty ……………………………………………………………………………….. starts releasing mature eggs in girls.
(a) Ovaries
(b) Testes
(c) Oviduct
(d) Sperm
Ans: (a)

Q4: Describe the development of secondary sex organs in males.
Ans: In males, sex organs like testes and penis develop completely at puberty. The testes begin to produce sperms.

Q5: Why do we observe acne or pimples on the face of young people at the age of adolescence?
Ans: During puberty, the secretion of sweat glands and sebaceous glands (oil glands) increases. Pimples are seen due to increased activity of these glands.

Case Study 2

Secondary Sexual: Characters You have learnt in Chapter 9, that testes and ovaries are the reproductive organs. They produce the gametes, that is, sperms and ova. In girls, breasts begin to develop at puberty and boys begin to grow facial hair, that is, moustaches and beard. As these features help to distinguish the male from the female, they are called secondary sexual characters. Boys also develop hair on their chest. In both, boys and girls, hair grows under the arms and in the region above the thighs or the pubic region. The changes which occur at adolescence are controlled by hormones. Hormones are chemical substances. These are secretions from endocrine glands, or endocrine system. The male hormone or testosterone begins to be released by the testes at the onset of puberty. This causes changes in boys about which you have just learnt, for example, the growth of facial hair. Once puberty is reached in girls, ovaries begin to produce the female hormone or estrogen which makes the breasts develop. Milk secreting glands or mammary glands develop inside the breasts. The production of these hormones is under the control of another hormone secreted from an endocrine gland called pituitary gland. Role of Hormones in Initiating Reproductive Function Endocrine glands release hormones into the bloodstream to reach a particular body part called target site. The target site responds to the hormone. There are many endocrine glands or ductless glands in the body. The testes and ovaries secrete sex hormones. You have just learnt that these hormones are responsible for the male and female secondary sexual characters. Further, the sex hormones are under the control of hormones from the pituitary gland. The pituitary secretes many hormones, one of which makes ova mature in the ovaries and sperms form in the testes.

Q1: Sex hormones are under the control of hormones from the ………………………………………………………………………………….. gland.
(a) Adrenal
(b) Pituitary
(c) Thyroid
(d) Thymus
Ans: (b)

Q2: Which among the following is the example of a major male sex hormone?
(a) Testosterone
(b) Estrogen
(c) Prolactin
(d) Follicle stimulating hormone
Ans: (a)

Q3: The endocrine gland is generally also known as ……………………………………………………………………………………….
(a) Superficial glands
(b) Doubtful glands
(c) Funny glands
(d) Ductless glands
Ans: (d)

Q4: Define the term “Hormone”.
Ans: Hormones are chemical substances that are secreted by endocrine glands or the endocrine system. They act as messengers to regulate various functions in the body.

Q5: Name some of the secondary sexual characters observed in girls.
Ans: Some of the secondary sexual characters observed in girls include the development of breasts, hair growth under the arms and in the pubic region, and the development of mammary glands inside the breasts.

Case Study 3

Reproductive Phase of Life in Humans: Adolescents become capable of reproduction when their testes and ovaries begin to produce gametes. The capacity for maturation and production of gametes lasts for a much longer time in males than in females. In females, the reproductive phase of life begins at puberty (10 to 12 years of age) and generally lasts till the age of approximately 45 to 50 years. The ova begin to mature with the onset of puberty. One ovum matures and is released by one of the ovaries once in about 28 to 30 days. During this period, the wall of the uterus be comes 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 bleeding in women which is called menstruation. Menstruation occurs once in about 28 to 30 days. The first menstrual flow begins at puberty and is termed menarche. At 45 to 50 years of age, the menstrual cycle stops. Stoppage of menstruation is termed menopause. Initially, menstrual cycle may be irregular. It takes some time to become regular. Menstrual cycle is controlled by hormones. The cycle includes the maturation of the egg, its release, thickening of uterine wall and its breakdown if pregnancy does not occur. In case the egg is fertilised it begins to divide and then gets embedded in the uterus for further development as you have learnt in Chapter 9 How is the Sex of the Baby Determined? Inside the fertilised egg or zygote is the instruction for determining the sex of the baby. This instruction is present in the thread-like structures, called chromosomes in the fertilised egg.RecallfromChapter8,thatchromosomes are present inside the nucleus of every cell. All human beings have 23 pairs of chromosomes in the nuclei of their cells. Two chromosomes out of these are the sex chromosomes, named X and Y. A female has two X chromosomes, while a male has one X and one Y chromosome. The gametes(egg and sperm) have only one set of chromosomes. The unfertilised 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. See Fig. 10.4. 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. Now you know that the sex chromosomes of the father determine the sex of an unborn baby. The belief that the mother is responsible for the sex of her baby is completely wrong and to blame her for this is totally unjustified.

Q1: The first menstrual flow begins at puberty and is termed as………………………………………………………………………………………..
(a) Menopause
(b) Premenstrual syndrome
(c) PCOD
(d) Menarche
Ans: (d)

Q2: If a baby has XY chromosomes in its nucleus, then the sex of the baby is?
(a) Female
(b) Male
(c) Both (a) and (b)
(d) None of the above
Ans: (b)

Q3: Which among the following is NOT an event of menstruation in females?
(a) Thickening of uterus wall
(b) Fertilisation of ovum and sperm
(c) Release of matured ovum
(d) Shedding of blood vessels and ovum
Ans: (b)

Q4: Explain in detail the process of menstruation.
Ans: In about 28-30 days, one ovum matures and is released from the ovary. The walls of the uterus are thickened to receive the ovum. If fertilisation does not occur, the released ovum, along with the thickened lining and its blood vessels, is shed off, causing bleeding.

Q5: Name the possible sex chromosomes present in the male and female gametes.
Ans: The sex chromosome present in the ovum (female gamete) is always an X chromosome. The sperm (male gamete) can carry either an X chromosome or a Y chromosome.

Case Study 4

Hormones other than Sex Hormones: The hormones secreted by the pituitary stimulate testes and ovaries to produce their hormones. You have already learnt that the pituitary gland is an endocrine gland.It is attached to the brain.Apart from the pituitary, the testesand the ovaries, there are otherendocrine glands in the body such as thyroid, pancreas and adrenals. Boojho and Paheli had once visitedtheir aunt who was a doctor and remembered that a boy named Kaka hada very big and bulging throat. Their aunt had told them that Kaka was sufferingfrom ‘goitre’, a disease of the thyroid gland. Kaka’s thyroid gland was notproducing the hormone thyroxine. Their aunt also told them that theiruncle was suffering from ‘diabetes’ because his pancreas was not producing the hormone insulin in sufficient quantities. Boojho and Paheli then asked their aunt about the adrenal glands, which are also shown in the chart hung on the wall of her clinic. Theaunt told them that adrenal glands secrete hormones which maintain the correct salt balance in the blood. Adrenals also produce the hormone adrenalin. It helps the body to adjust to stress when one is very angry, embarrassed or worried. Thyroid and adrenals secrete their hormones when they receive orders from the pituitary through its hormones. Pituitary also secretes growth hormone which is necessary for the normal growth of a person. Role of Hormones in Completing the Life History of Insects and Frogs: You have already learnt about the life history of the silk moth and the frog. The caterpillar has to pass through various stages to become an adult moth. Recall from Class VII the stages of the life history of the silk moth. Similarly, the tadpole passes through certain stages to become a frog (Chapter 9).This change from larva to adult is called metamorphosis (Fig. 9.10).Metamorphosis in insects is controlled by insect hormones. In a frog, it is controlled by thyroxine, the hormone produced by thyroid. Thyroxine production requires the presence of iodine in water. If the water in which the tadpoles are growing does not contain sufficient iodine, the tadpoles cannot become adults.

Q1: If the thyroid gland of a person is not producing thyroxine hormone, he/she is suffering from………………………………………………………………………………..
(a) Goitre
(b) Mumps
(c) Chicken pox
(d) Diabetes
Ans: (a)

Q2: Metamorphosis in frogs is controlled by which of the following hormones?
(a) Insulin
(b) Testosterone
(c) Estrogen
(d) Thyroxine
Ans: (d)

Q3: In a person suffering from Diabetes, the pancreas does not produce …………………………………………………………………………………….. hormone in sufficient quantity.
(a) Adrenalin
(b) Thyroxine
(c) Insulin
(d) Melatonin
Ans: (c)

Q4: Explain the role of adrenal glands.
Ans: Adrenal glands produce the hormone adrenalin, which helps the body adjust to stress when a person is angry, embarrassed, or worried.

Q5: Name some of the endocrine glands in the human body.
Ans: Some of the endocrine glands include: Thyroid, pancreas, adrenal, testes, ovary, and pituitary gland.