Reaching The Age of Adolescence NCERT Solutions - Class 8 Science
NCERT Solutions for Class 8 Science Chapter 10 - Reaching The Age of Adolescence
NCERT Solutions for Class 8 Science Chapter 10 Reaching the Age of Adolescence is the study guide that is most beneficial for those students who are facing problems in preparing for their exams. These materials consist of solutions to all of the appropriate questions contained in the NCERT textbooks. Students may also prepare their revision notes as well as other homework assignments by getting these solutions in pdf format free from Vedantu. When you grow up, it becomes essential to understand the modifications occurring all around as well as within you. This chapter is targeted at the hormonal alterations that take place in the body of youngsters between the ages of 11 and 19 years.
The solutions prepared by the expert faculty members at Vedantu include the explanations to all of the questions within the CBSE class 8 textbook. The explanations are presented by the professionals in a manner that is methodical and in accordance with the updated CBSE syllabus and guidelines. Each question is dealt with in the minutest of details by the expert faculties at Vedantu. Students can reference this solution manual before exams and cover the entire chapter in a very short time. The solutions supplied are undoubtedly perfect for quick revision. First, learn the exercises and concepts provided in the text by yourself. Refer to the solutions if you fail to understand any concept or cannot understand the answer to any particular question.
Chapter 8 - Reaching the Age of Adolescence
This chapter on attaining puberty in humans consists of the following topics:
10.1 Adolescence and Puberty
10.2 Changes at Puberty Increase in Height
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
The chapter starts with asking the students to recall how in the previous chapter they learnt exactly how animals produce offspring. It is mentioned that only after reaching a certain age human beings and many other animals get the capability to reproduce. After that the students are asked the question why this happens, that humans become capable of reproducing only when they grow up and attain that particular age. It is mentioned here that this chapter will cover the modifications that take place in the human body, which makes them become effective at reproducing. Then the learning of Chapter 9 is reminded, where the students studied the reproductive organs of human beings. Then it is clarified that in this chapter the function of hormones in bringing about the changes that cause a child to grow into an adult human being happen will be discussed.
Adolescence and Puberty
The chapter discusses the important concepts through the activities and thoughts of two siblings Boojho and Paheli. A scenario is mentioned here I n which Boojho celebrated his 12th birthday party with his friends. After those friends went back home his sister Paheli started laughing. Paheli is mentioned to study in an all-girls school and hence she is unaware of the adolescent phase of boys. She makes a comment here that a number of Boojho’s friends whom she met after a whole year had suddenly soared up in stature. Appearance of thin hairy lines above their lips where a moustache grows made some of their appearances comical. Then their mother is mentioned and in her words, the concept of attaining puberty is explained in brief. She explains that the boys had grown up. It is mentioned that growth occurs from the very first day of a person’s life. However, it is only after turning 10 or 11 years old, a spurt of growth occurs that makes the changes in the human body noticeable. It is explained that the changes happening in the anatomy is a part of growth. It is clarified that these changes are a sign that the individual is no longer a child but has started on their journey to attain adulthood.
It is written next that the process of growing up is natural. There is a special name for the phase of life in which the body goes through changes and reproductive organs get matured. The term is mentioned as adolescence. It is explained that adolescence starts at around the age of 11 and goes on up to the age of 18 or 19 years. Then it is clarified that since this phase covers the teens of a person’s life, thirteen to eighteen or nineteen, the adolescents are also known as teenagers. It is stated that in girls adolescence often starts a couple of years before it occurs in boys. It is also stated that the time of adolescence is not the same for everyone. The changes that take place in the human body during adolescence mark the onset of puberty. The most important occurrence that symbolizes puberty is that girls and boys gain the ability of reproduction. Puberty terminates when the adolescent attains complete reproductive maturity.
Changes at Puberty
Increase in Height
In this section of Class 8 Science Chapter 10 Solutions, it is stated that the sudden rise in height is the most striking change that happens to the human body at the time of puberty. The long bones of the body that is the bones of arms and legs become long and make the person tall at this period of growth. A chart is provided depicting the average rate of growth in girls and boys according to age. It is also mentioned that the numbers given in this chart a representative, and there might be variations from one individual to another. Then the method of calculating the full height of a person is provided.
It is mentioned next in this segment that at first girls show faster growth. However, by the time the age of 18 is reached, both girls and boys reach their maximum height. The rate of growth is not the same for everyone, some people grow faster than others do. Some might increase in height all of a sudden when puberty comes and then their growth may taper off, while others may show a gradual increase in height.
Next, Paheli is shown to be worried that though her body has become tall, her face appears smaller in comparison to her body. Nevertheless, the chapter gives reassurance that there is no reason to worry. Not all parts of the body show growth at the identical rate. Often the limbs that are he arms and legs, or the hands and feet of teenagers appear out of proportion with the body. Nevertheless, the other parts catch up in growth quickly and in the end, the body becomes proportionate. It is then mentioned that the height of a person might resemble that of some other members of the family. The explanation for this is given as the fact that height depends on genes that the parents transfer to the children. It is also mentioned that it is vital to eat proper nutritious food all through the growing phase. The different parts of the body like the bones, muscles and other such parts get sufficient sustenance for adequate growth from the healthy food. It is mentioned here that the needs for nutrition in adolescents are discussed at a later part of the lesson.
Change in Body Shape
The students are asked if they have noted that the boys in their class have wider shoulders and broader chests than those of the boys in junior classes. The reason is given as the entrance to the age of puberty. Growth causes the shoulders to widen. It is then mentioned that in girls the portion of the body under the waist turn wider. It is also revealed that in boys the growth of the muscles is more noticeable than in the girls. It is mentioned that the alterations that occur in adolescent boys and girls are not the same.
The students are asked if they have noticed that some of their male classmates have a crack in their voices. The reason is given as the growth of the voice box or the larynx during puberty. It is stated that larger voice boxes develop in the boys. This growing voice box often becomes visible as a protruding part on the throat names as the Adam’s apple. Conversely, in girls the voice box can be hardly seen from outside owing to its petite size. It is then mentioned that in usual scenarios the girls are found to have high-pitched voice while the boys develop a deep voice. The occurrence of voice becoming hoarse in some cases is also talked about. The reason is cited as the muscles in the voice box going out of control. It is mentioned that this hoarseness may remain for days or weeks and then voice becomes normal.
Increased Activity of Sweat and Sebaceous Glands
In this segment of NCERT Class 8 Science Chapter 10 it is mentioned that at the time of puberty the activity of sweat glands and oil glands known as sebaceous glands in the skin become enhanced and their secretion increases. This increased activity of these glands is mentioned as the reason why many young people start to get acne and pimples on their face during puberty.
It is then clarified that some of the glands like sweat glands, oil glands and salivary glands discharge their secretions through ducts. However, the endocrine glands release hormones straight into the bloodstream. For this reason the endocrine glands are also known as ductless glands.
Development of Sex Organs
The students are requested to turn to the previous chapter and view the diagrams that depict the sex organs of human beings. It is then mentioned that the male sex organs such as the testes and the penis become fully developed. It is also stated that the tested starts to synthesize sperms. It is also mentioned that the ovaries in girls become large in size and the eggs start to mature. The ovaries then start to release the mature eggs.
Reaching Mental, Intellectual and Emotional Maturity
In this segment of NCERT Class 8 Science Chapter 10 it is then mentioned that adolescence is the time when an individual’s thought process changes. The adolescents are more independent than children and also self-conscious, feeling awkward much of the time. Intellectual maturity occurs and the young people have the tendency to spend long time thinking. It is mentioned that in most cases this is the time of a person’s life when their brain has the highest capacity to learn. Feelings of insecurity often creep into the minds of adolescents as they attempt to get used to and adjust to the changes in their bodies and minds. The lesson then reassures the adolescent learners that there is no cause to feel insecure and that the modifications are nothing but a natural part of the process of growth.
Secondary Sexual Characters
This segment brings to the reader’s mind that they had studied about testes and ovaries, the reproductive organs, in the previous chapter. It is mentioned that the reproductive organs produce the gametes, namely, the sperm and ova. the students are informed that facial hair, which is a moustache and beard, starts to grow in boys, while girls begin to develop breasts at this stage of their life known as puberty. It is then explained that since these features help in differentiating between girls and boys these are known as secondary sexual characters. It is then stated that boys develop hair on their chest while both boys and girls, body hair develops under their arms and in the pubic region which Is the part of the body above the thighs.
This section explains that the changes that happen at adolescence are caused by hormones that are chemical substances. It is clarified that the hormones are secreted from endocrine glands that make up the endocrine system. At the beginning of puberty the testes starts to release the male hormone known as testosterone. This hormone is responsible for all the changes that happen in the body of a boy as discussed in the lesson so far. The instance of growth of facial hair is cited. It is then mentioned that at the onset of puberty in girls, the ovaries start to secrete the female hormone known as estrogen that is responsible for the development of breasts. The breasts have the milk secreting mammary glands inside them. It is also mentioned that the secretion of these hormones are controlled by another hormone that is produced from and endocrine gland called the pituitary gland.
Role of Hormones in Initiating Reproductive Function
The function and workings of hormones are explained in detail in this section of the chapter 10. It is elucidated that the hormones come out of the endocrine glands directly into the bloodstream and then reach a specific part of the body, which is their site of action, known as the target site. The target site responds to the hormone. It is stated that there are several ductless endocrine glands in the body.
The students are reminded that the testes and the ovaries produce the sex hormones that bring about the male and female secondary sexual characters, and that the sex hormones are controlled by the hormones secreted from the pituitary gland. It is then clarified that the pituitary gland releases a number of hormones, one of which causes the ova to mature in the ovaries and sperm to form in the testes.
The next question to ponder is whether reproductive life, after it starts, goes on or gets terminates after some time.
Reproductive Phase of Life in Humans
In this section of NCERT Science Class 8 Chapter 10 it is explained that adolescent young people get the capability of reproduction when gametes start getting produced from their testes and ovaries. It is mentioned that the ability to produce gametes lasts longer in males than in females. The reproductive phase of life in females starts at the age of 10 to 12 years at the onset of puberty. It generally remains till the females reaches about 45 to 50 years of age. When puberty starts the ova begins to get matured. In every 28 to 30 days, one ovum becomes mature and gets released from one of the ovaries. At this time the wall of the uterus thickens to enable it to receive the egg, in preparation of fertilization and further developments. If this occurs then pregnancy happens. However, if fertilization does not take place, the released mature egg and the thickened lining of the uterus along with its blood vessels are shed. This results in monthly bleeding in women, which is referred to as menstruation. It occurs every 28 to 30 days. The first menstrual flow that starts at puberty is called menarche. At the age of 45 to 50 the menstrual cycle ceases to happen. This occurrence is known as the menopause. In the first stages the menstrual cycle is often irregular and takes some time to regularise. Role of hormones in the menstrual cycle is then mentioned and the details of the cycle are discussed. it is mentioned that the steps of the cycles consist of the maturation of the egg, its release, thickening of the walls of the uterus, and it's getting shed when pregnancy does not take place. When the egg does get fertilised it starts to divide and then it gets embedded in the uterus as the students had learnt in the previous chapter.
How is the Sex of the Baby Determined?
This section details the process of how the sex of a baby gets determined. It is mentioned that the instruction for determining the gender of the baby resides inside the fertilised egg called the zygote. The instruction is contained within the thread-like structures known as the chromosomes that are present inside the fertilised egg. The students are asked to remember that in a previous lesson they were taught that inside the nucleus of every cell chromosome are present. It is then discussed here that in the nuclei of the cells all human beings have 23 chromosomes. Two of these are called sex chromosomes and are named X and Y. It is mentioned that two X chromosomes are present in the female while a male has one each of the X and Y chromosomes. It is then clarified that the gametes each have only one chromosome, coming from the female, the unfertilized egg bears only the one X chromosome. However, sperms are of two types. One kind contains the X chromosomes, while the Y ones are present in the other kind. From this it becomes clear that when a sperm that contains the X chromosomes unites with the ovum and fertilizes it the zygote bears two X chromosomes and develops into a female baby. However, if the sperm brings the Y chromosome to the egg during fertilization, the zygote would grow into a male child. From this it is evident that the sex chromosome of the father is responsible for the determination of sex of the unborn child. The uninformed belief that the mother is responsible for the gender of the baby is totally unfounded and it is wrong to blame her for the sex of the child.
Hormones other than Sex Hormones
It is reiterated in this section that the hormones released by the pituitary stimulate testes and ovaries to secrete their hormones. Students are already aware that the pituitary gland is an endocrine gland. Here it is mentioned that it is attached to the brain. It is further discussed that in addition to the pituitary, the testes and the ovaries, there are other endocrine glands in the body of humans. The examples include the thyroid, pancreas and adrenals. Boojho and Paheli are again mentioned in this context, and their visit to a doctor is described. This section explains that when the thyroid gland fails to produce the hormone called thyroxine, the disease called goiter results, which causes a big and bulging throat. It is also mentioned that when the pancreas does not produce the hormone in sufficient quantities the disease diabetes results. Then the role of the hormones secreted from the adrenals in maintaining the correct balance of salt in the blood is mentioned. The hormone adrenaline released from adrenals is also named here and its role in enabling the body to adjust to stress is explained. It is also explained that the pituitary orders the thyroid and the adrenals to secrete their hormones. The secretion of the growth hormone from the pituitary that is vital for the normal growth of a person is also mentioned.
Role of Hormones in Completing the Life History of Insects and Frogs
The students are reminded that they have learnt about the life history of the silk moth and the frog. It is mentioned that the caterpillar has to go through different stages to turn into an adult moth. It is mentioned that likewise the tadpole goes through definite stages to develop into a frog. It is mentioned that this alteration from larva to adult is identified as metamorphosis. It is then discussed that insect hormones govern metamorphosis in insects. In a frog, a hormone secreted from the thyroid gland called thyroxine controls it. It is stated that production of thyroxine is dependent on the presence of iodine in water. Unless the water in which the tadpoles are growing contains sufficient iodine the tadpoles fail to develop into adults.
Health is the physical and mental well being of a person. Balanced diet is essential to keep the body of a human being at any age healthy. Maintaining personal hygiene and undertaking physical exercise are essential for good health. It is mentioned that these are even more vital at the adolescent period because the body is growing at this stage.
Nutritional Needs of the Adolescents
Rapid growth and development happens during adolescence. Thus it is essential to plan the diet of an adolescent carefully. The students are instructed to recall that a balanced diet contains proteins, carbohydrates, fats and vitamins in appropriate proportions. It is mentioned that the Indian meal of roti or rice, dal or pulses and vegetables is a balanced meal. Milk is stated to be a balanced food in itself. Fruits are named as sources of nutrition. Iron is needed to build blood and iron-containing food like jaggery, citrus, leafy vegetables, the Indian gooseberry and meat are important for adolescents. Cereals are explained as sources of energy and milk, meat, nuts and pulses as sources of protein for growth. Fats and sugars are also named as sources of energy and fruits and vegetables as protective foods.
The importance of not replacing regular meals with chips and packed or tinned snacks, though tasty Is underscored as the processed foods have inadequate nutrition.
Having a bath once a day is important but it is mentioned that bathing regularly is even more essential in adolescents because the body can become smelly from the excessive activity of the sweat glands. Cleanliness is stated as important because it prevents infections. Special care of cleanliness during menstrual flow in girls is stressed and they are advised to keep track of their menstrual cycle and stay prepared for the commencement of menstruation.
Importance of exercises like walking and playing in the fresh air keeps is mentioned in this section.
Say “NO” to Drugs
The various harmful effects of drugs are explained and the students are urged to refuse taking drugs unless prescribed by doctors. It is explained that how taking drugs can become addictive and ruin the health and happiness of an affected individual. Different routes through which HIV infection spreads are also discussed in brief.
The adverse effects of teenage pregnancies are explained in some detail. The legal age for marriage as 18 for girls and 21 for boys and the need for it from the health point of view are stated. Health problems as well as mental agony associated with teenage pregnancies are discussed in this section.
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