The DAV Class 8 Science Solutions and DAV Class 8 Science Chapter 15 Question Answer – Reaching the Age of Adolescence are essential study tools for DAV public school students in Class 8.
DAV Class 8 Science Ch 15 Question Answer – Reaching the Age of Adolescence
DAV Class 8 Science Ch 15 Solutions – Reaching the Age of Adolescence
Something To Know
A. Fill in the blanks:
Question 1.
Endocrine glands release ________ into the blood stream.
Answer:
hormones
Question 2.
________ is also known as the voice box.
Answer:
larynx
Question 3.
Acne and pimples are common in adolescence due to increased production of ________ by the ________ glands.
Answer:
oil, sebaceous
Question 4.
Deficiency of ________ reduces the absorption of calcium by the body.
Answer:
vitamin D
Question 5.
________ hormone is essential for metamorphosis to happen in a frog.
Answer:
Thyroxine
Question 6.
________ are chromosomes other than the sex chromosomes.
Answer:
autosomes
B. Match the following:
| Column I | Column II |
| (1) Ovary | (a) Adrenaline |
| (2) Pancreas | (b) Testosterone |
| (3) Adrenals | (c) Thyroxine |
| (4) Testes | (d) Insulin |
| (5) Thyroid | (e) Progesterone |
Answer:
| Column I | Column II |
| (1) Ovary | (e) Progesterone |
| (2) Pancreas | (d) Insulin |
| (3) Adrenals | (a) Adrenaline |
| (4) Testes | (b) Testosterone |
| (5) Thyroid | (c) Thyroxine |
C. Tick (v) the correct option:
Question 1.
The period of life, marked by rapid changes leading towards sexual maturity, known as—
(a) Childhood
(b) Old age
(c) Puberty
(d) Adulthood
Answer:
(c) Puberty
Question 2.
The onset of menstruation, in a human female, is known as-
(a) Menarche
(b) Ovulation
(c) Menopause
(d) Adolescence
Answer:
(c) Menarche
Question 3.
The hormone, which controls the body’s response to stress, is known as—
(a) Insulin
(b) Thyroxine
(c) Estrogen
(d) Adrenaline
Answer:
(d) Adrenaline
Question 4.
Out of the following, the one that does not produce hormones, is the-
(a) Thyroid gland
(b) Sebaceous glands
(c) Pineal gland
(d) Testes
Answer:
(b) Sebaceous glands
Question 5.
The mineral, whose presence is essential for a tadpole to grow into a frog, is-
(a) Calcium
(b) Chlorine
(c) Selenium
(d) Iodine
Answer:
(d) Iodine
D. Answer the following questions in brief:
Question 1.
State the meaning of the term ‘Adolescence’.
Answer:
The period of transition from childhood to adulthood is called adolescence.
Question 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.
Question 3.
Why are endocrine glands known as ductless glands?
Answer:
Endocrine glands directly release their secretion in blood stream. Hence, they are called ductless glands.
Question 4.
Why do tadpoles growing in iodine deficient waters fail to grow into frogs?
Answer:
Iodine is an important component of thyroxine, and thyroxine is necessary for metamorphosis of tadpole into frog. Deficiency of iodine in water results in deficiency of the hormone thyroxine. This results in failure of metamorphosis of tadpole into frogs.
Question 5.
How does the pituitary gland control the maturation of the gonads?
Answer:
Pituitary gland secretes Gonadotropic hormone which stimulates the development of gonads.
Question 6.
Women, above the age of fifty, are (generally) unable to give birth to children. Explain the reason for the same.
Answer:
Menstrual cycle generally ceases in women by the time they attain the age of fifty. This marks the end of reproductive phase. Hence, women above the age of fifty are generally unable to give birth to children.
E. Answer the following questions:
Question 1.
Enlist the changes which occur in males and females during puberty.
Answer:
Changes in males:
• Shoulders become broad.
• Body becomes muscular.
• Hairs grow on face, under armpits and in 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 armpit and in pubic region.
Question 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?
Answer:
(a) Arunima is suffering from goitre which happens because of deficiency of iodine.
(b) Adam’s Apple has developed in Arun. It is a normal development in boys. Hence, Arun does not need medications.
Question 3.
Discuss how the sex of the unborn child gets determined in human beings.
Answer:
The somatic cell in human beings contain 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 a 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.
Question 4.
Enlist the events that regularly occur in the female reproductive system, after the onset of puberty, until menopause.
Answer:
The cycle of events which generally happens over every 28 days is called 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 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 uterus is shed in fragments. All these matter are released out through the vagina. This called menstruation. Menstruation lasts for 3-6 days.
Question 5.
Highlight the importance of exercise and good personal hygiene during adolescence.
Answer:
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. 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
Amit and Sumit are good friends since their childhood. Amit dreams of becoming a cricketer. He is extremely fond of junk food and loves to eat fries, pastas and burgers, both for his lunch as well as for his dinner. He avoids eating fruits and vegetables and drinking milk. Sumit feels very concerned about his friend. He warns him that he is running his health and may end up being an unhealthy adult instead of a sportsperson. He helps Amit to change his food habits so that he may fulfil his dream.
Question 1.
State the values shown by Sumit.
Answer:
Sumit shows a concern for his friend.
Question 2.
State the problems that Amit may face as an adult.
Answer:
Amit may become obese and may suffer from diabetes or hypertension.
Question 3.
State the importance of fruits, vegetables and milk in one’s diet.
Answer:
Fruits and vegetables are important sources of important vitamins and minerals. Milk is the main source of calcium in our diet. Hence, fruits, vegetables and milk are necessary for balanced diet. It is important to take a balanced diet for proper growth and development, especially during adolescence.
Question 4.
Arrange a ‘street play’ to highlight the importance of a ‘balanced and healthy diet’.
Answer:
Do it yourself.
Something To Do
Question 1.
Why is sex determination of the unborn foetus banned by the government? Visit a nearby hospital and discuss this issue with the resident doctor.
Answer:
Majority of people prefer a male child in India. Many people resort to abortion if they find that it is a female foetus. This has resulted in eschewed sex ratio in the country. Due to this, sex determination of the unborn foetus has been banned by the government.
Question 2.
Collect information about the ‘Say No to Drugs’ campaign and prepare a display board using the details of this information.
Answer:
Do it yourself
Question 3.
There are various myths related to changes in the body that occur during adolescence. Make a list of such myths and discuss in your class why these myths should not be believed.
Here is one: ‘A menstruating girl is impure and hence, should not enter the kitchen.’
Answer:
Do it yourself.
Question 4.
Find out the sex ratio of your state. Compare it with the state having the best ratio and discuss in class, the probable reasons for the observed values of the ratios in both the states.
Answer:
Do it yourself.
Question 5.
“Adolescence: A unique phase marked by concerns and challenges.” Have a group discussion on the above mentioned topic.
Answer:
Do it yourself.
Question 6.
Search for the following in the word search puzzle given below
(a) Period of transition from childhood to adulthood.
(b) Reaching the age of sexual maturity.
(c) Gland which releases the growth hormone.
(d) Disease caused due to deficiency of a pancreatic hormone.
(e) Reproductive organs.
(f) This hormone controls the metabolic rate.
(g) Voice box.
(h) Disease caused by deficiency of calcium and vitamin D.
(i) Onset of puberty in females.
(j) Transition of tadpole into a frog.
(k) Stress regulating hormone.
(l) Male gamete.
(m) Chromosomes other than sex chromosomes.
(n) Hormone produced by the pancreas.
Answer:
(a) Puberty
(b) Adolescence
(c) Pituitary
(d) Diabetes
(e) Gonads
(f) Thyroxine
(g) Larynx
(h) Osteoporosis
(i) Menarche
(j) Metamorphosis
(k) Adrenaline
(i) Sperm
(m) Autosomes
(n) Insulin
DAV Class 8 Science Chapter 15 Solutions – Reaching the Age of Adolescence Important Questions and Answers
I. Fill in the blanks:
1. ________ differentiate a human male from a female.
Answer:
Secondary sexual characters
2. Larynx becomes ________ in males during adolescence.
Answer:
Enlarged
3. ________ produce sperms.
Answer:
Testes
4. ________ produce ovum.
Answer:
Ovaries
5. Fertilization takes place in ________ in the female reproductive system.
Answer:
Fallopian tube
6. The first menstrual flow is called ________ .
Answer:
Menarche
7. ________ marks the end of reproductive phase in females.
Answer:
Menopause
II. Tick the correct answer:
Question 1.
Which bones grow the fastest during adolescence?
(a) Long bones
(b) Pelvic bones
(c) Backbone
(d) Ribcage
Answer:
(a) Long bones
Question 2.
Heightened activity of which gland can lead to pimples?
(a) Sweat glands
(b) Sebaceous glands
(c) Pineal gland
(d) Adrenal gland
Answer:
(b) Sebaceous glands
Question 3.
Secretion from which gland prepares the body for emergency?
(a) Pituitary
(b) Thyroid
(c) Adrenal
(d) Pancreas
Answer:
(c) Adrenal
Question 4.
Which gland secretes the growth hormone?
(a) Pituitary
(b) Thyroid
(c) Testes
(d) Adrenal
Answer:
(a) Pituitary
Question 5.
Which of these minerals is more important for females?
(a) Calcium
(b) Iron
(c) Phosphorus
(d) Magnesium
Answer:
(b) Iron
III. Answer the following questions:
Question 1.
Which changes in the body shape become apparent during adolescence in boys and girls?
Answer:
Boys generally develop larger bones, more muscles, larger head and lungs; as compared to girls. Boys also develop broad shoulders and narrow hip, while the girls develop a curvaceous body and broader hips due to enlargement of pelvic bones.
Question 2.
What is menstrual cycle?
Answer:
The sequence of events which start with the release of an ovum and culminates in discarding the ovum if no pregnancy takes place is called menstrual cycle.
Question 3.
Explain the developments if fertilization occurs in the human female reproductive system.
Answer:
The fertilization occurs in the fallopian tube. After fertilization, zygote undergoes several rounds of cell division till it becomes a ball of cells. This is called embiyo. The embryo then enters the uterus and gets implanted in the uterine wall. This is called conception and marks the beginning of pregnancy. The embryo develops further to resemble a human being. At this stage, it is called a foetus.
Question 4.
What are the durations of reproductive phase in human male and female?
Answer:
The reproductive phase in women lasts till about 45 to 50 years of age. The reproductive phase in men lasts longer and it can be up to 70 years of age.
Question 5.
What happens if fertilization does not take place?
Answer:
The additional layers in the uterine wall get broken and shed in fragments. The ovum; along with fragments of the extra layer of the uterine wall; is shed along with blood through vagina. This is called menstruation.
IV. Projects:
Question 1.
Make a list of food which can give proper nutrition to an adolescent.
Answer:
Do it yourself
Question 2.
Make a list of harmful effects which a narcotic can have on a person.
Answer:
Do it yourself.