Chapter 15| Reaching The Age Of Adolescence | Class- 8 DAV Science Solutions

Are you looking for DAV Books Solutions then you are in right place, we have discussed the solution of Science class 8 book Chapter 15 Reaching the Age of Adolescence which is followed in all DAV School. Solutions are given below with proper Explanation please bookmark our website for further updates!! All the Best !!

DAV Class- 8 | Reaching the Age of Adolescence Question and Answer

Something To Know

A. Fill in the blanks:

1. Endocrine glands release hormones into the blood stream.

2.Larynx is also known as the voice box.

3.Acne and pimples are common in adolescence due to increased production of oil by the sebaceous glands.

4. Deficiency of vitamin D reduces the absorption of calcium by the body.

5. Thyroxine hormone is essential for metamorphosis to happen in a frog.

6. Autosomes are chromosomes other than the sex chromosomes.

B. Match the following statements:

Ans:

Column I	Column II
Ovary	Progesterone
Pancreas	Insulin
Adrenals	Adrenaline
Testes	Testosterone
Thyroid	Thyroxine

C. Tick the correct Option:

1. The period of life, marked by rapid changes leading towards sexual maturity, is known as—❑ Childhood ❑ Old age ❑ Puberty ❑ Adulthood

Ans. Puberty

2. The onset of menstruation, in a human female, is known as—❑ Menarche ❑ Ovulation ❑ Menopause ❑ Adolescence

Ans. Menarche

3. The hormone, which controls the body’s response to stress, is known as—❑ Insulin ❑ Thyroxine ❑ Estrogen ❑ Adrenaline

Ans. Adrenaline

4. Out of the following, the one that does not produce hormones, is the—❑ Thyroid gland ❑ Sebaceous glands ❑ Pineal gland ❑ Testes

Ans. Sebaceous glands

5. The mineral, whose presence is essential for a tadpole to grow into a frog, is—❑ Calcium ❑ Chlorine ❑ Selenium ❑ Iodine

Ans. Iodine

D. Answer the following questions in brief:

1. State the meaning of the term ‘Adolescence’.

Answer: Adolescence is the stage of transition from childhood to adulthood.

2. Define puberty. State the various factors which influence it.

Answer: The initial phase of adolescence is marked by certain dramatic changes in the body. This period is called puberty. Proper diet, genes, and environment influence this period.

3. Why are endocrine glands known as ductless glands?

Answer: Endocrine glands are also known as ductless glands as they do not have any ducts of their own; they pour their secretions directly into the bloodstream.

4. Why do tadpoles growing in iodine deficient waters fail to grow into frogs?

Answer: Tadpoles growing in iodine-deficient waters fail to grow into frogs because Iodine is needed for the production of thyroxine and the hormone ‘thyroxine, produced by the thyroid gland of the frog, is essential to carry out the process of metamorphosis.

5. How does the pituitary gland control the maturation of the gonads?

Answer: Pituitary gland in the brain secretes hormones that activate the ovaries and the testes to produce estrogen, progesterone, and testosterone. These hormones help in the maturation of the gonads.

6. Women, above the age of fifty, are (generally) unable to give birth to children. Explain the reason for the same.

Answer: The menstrual cycle stops when the woman reaches 45-50 years of age. This marks the end of the reproductive phase. Hence, women above the age of fifty are generally unable to give birth to children.

E. Answer the following questions.

1. Enlist the changes which occur in males and females during puberty.

Ans. Changes in males: • Shoulders become broad. • Body becomes muscular. • Hairs grow on the face, under armpits, and in the pubic region. • Gonad matures and starts producing sperms. • Height increases significantly. • Voice becomes deep. Change in females: • Hips become wide. • Breasts get enlarged. • Menstruation begins. • Hairs develop under the armpit and in the pubic region.

2. Arun and his sister Arunima are both teenagers’. Arunima observes a swelling on her neck, following which she visits a doctor. The doctor identifies it to be a deficiency disease and prescribes medicines accordingly, along with suggesting dietary modifications. A few months later, Arun observes a small protrusion on his throat and visits the doctor. However, the doctor assures him that it is a normal feature in boys of his age. (a) Identify the disease Arunima was suffering from along with its cause. (b) Why do you think that no medication was prescribed for Arun?

Ans. (a) Arunima is suffering from goitre which happens because of a deficiency of iodine. (b) Adam’s Apple has developed in Arun. It is a normal development in boys. Hence, Arun does not need medications.

3. Discuss how the sex of the unborn child gets determined in human beings.

Ans. The somatic cell in human beings contains 23 pairs of chromosomes. Out of them, the 23rd pair contains sex chromosomes. A sperm or an egg contains 23 chromosomes. The 23rd chromosome in sperm can either be X or Y chromosome. The 23rd chromosome in an egg is always an X chromosome. When a sperm with X chromosome fertilizes the egg, the zygote develops into a female child. When a sperm with Y chromosome fertilizes the egg, the zygote develops into a male child.

4. Enlist the events that regularly occur in the female reproductive system, after the onset of puberty, until menopause.

Ans. The cycle of events that generally happens every 28 days is called the menstrual cycle. One egg from either of the ovaries becomes mature at the beginning of a menstrual cycle. The egg is released by the ovary and it reaches the oviduct. The uterus prepares for a possible pregnancy by making a thick lining of blood vessels. If fertilization does not take place then at the end of the cycle, the egg, along with the lining of the uterus is shed in fragments. All these matters are released out through the vagina. This is called menstruation. Menstruation lasts for 3-6 days.

5. Highlight the importance of exercise and good personal hygiene during adolescence.

Ans. Exercise is necessary for people of every age group. But an adolescent needs to do regular exercise in order to keep the body in good condition. It helps in attaining optimum growth. The adolescence period is the period of increased activity of sebaceous glands and sweat glands. This often causes the problem of pimples and acne. Body odour can be another problem. Maintaining good personal hygiene helps in preventing these problems. Girls should take special care of hygiene during menstruation.

Value Based Question

Do it yourself

Chapter 15| Reaching the Age of Adolescence | Class- 8 DAV Science Solutions