Biology
CLASS VIII
L-10: REACHING THE AGE OF ADOLESCENCE
NOTE-BOOK WORK
Q1. What is adolescence? (SOC)
Ans. The period of life, when the body undergoes changes, leading to reproductive maturity, is
called adolescence.
• This is the time span in which the child develops into an adult.
• Adolescence begins around the age of 11 and goes on until 18 or 19 years of age.
Q 2. What is puberty? What is the most conspicuous visible change in boys during
puberty?
Ans. Puberty is the period, during which, the human body undergoes certain changes in their
body and reproductive organs which leads to sexual maturity.
The most conspicuous visible change in boys during puberty is increase in height .
Q3. Differentiate between changes in body of adolescent boys and girls. (Web Chart)(SOC)
Ans.
Boys GIRLS
The growth of facial
Enlargement of breasts
hair.
The growth of body hair The growth of body hair,
including underarm, prominently in the underarm and
abdomen, chest hair and pubic areas.
pubic hair.
Widening of hips
Chest and shoulders widen
and body becomes muscular
Changed fat distribution. More fat
Skin becomes more rough and below the skin, at hips, buttocks and
porous, secretion of sweat thighs.
glands and sebaceous glands
increase
Development of secondary
Larynx (Adam’s apple)/voice reproductive organs.
box protrudes out and voice
becomes deep and husk.
Q4Differentiate between Endocrine and exocrine glands
Endocrine Glands Exocrine glands
Endocrine glands do not have ducts Exocrine glands have ducts
Secretory Products are in the form of Secretory Products are in the form of
Hormones. sweat, enzymes, mucus, sebum.
Secretory products released directly Secretory products are released to an
into the bloodstream, eventually internal organ or the external surface
reaching the target organ. through a duct.
thyroid glands, pituitary glands, salivary glands, sweat glands
adrenal glands.
Q5. What are Hormones? What is the specific action of hormones? (SOC)
Ans. Hormones are chemicals synthesized and produced by the specialized glands to control and
regulate the activity of certain cells and organs. These specialized glands are known as endocrine
glands.
• Changes that occur during adolescence are controlled by hormones.
• In males, the testes secrete the male hormones or the testosterone.
• In females, the ovaries secrete the female hormones or the estrogen.
Q6. Mention the reproductive phase in the life of a man and woman.
• Ans. In males and females, the reproductive stage commences at puberty.
• In girls, commencement of puberty is marked by the onset of menstruation or the
Menstrual cycle.
• The reproductive stage in females ceases by the age of 45-50 years.
• In males, however, the reproductive stage lasts for life.
Q7. Define and describe menstrual cycle in females.
• It is a reproductive cycle of females.
• It begins at puberty and the onset of the menstrual cycle is called as ‘menarche’.
• The process includes cyclic changes in the ovaries and in the uterus, both simultaneously.
• In the ovaries, an ovum develops and matures and then released.
• In the uterus, a thick spongy inner lining develops
• 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.
• The menstrual cycle stops in women anywhere between 45 to 52 years.
• Stopping of the menstrual cycle is called as ‘menopause‘.
Q8. Explain the process of sex determination in humans.
• All human beings have 23 pairs of chromosomes in the nuclei of their cells.
• Two chromosomes out of these are of 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 have only one set of chromosomes.
• The unfertilised ovum always has one X chromosome.
• But in the male gametes or sperms, there exists one kind having an X chromosome and the
other kind having a Y chromosome.
• So if the sperm that contains a Y chromosome fertilizes with the egg which contains the X
chromosome, the zygote develops into a male.
• On the other hand, if the sperm contains an X chromosome and fertilizers with the egg
which contains X chromosome, the zygote develops into a female.
• Hence the sex of the child depends upon the chromosomes of the father and not the
mother.
Q9. Give scientific reason: Adrenaline is called stress hormone.
Ans. Adrenaline is known as stress hormone because it is released when stress arises in our
body, so it helps to increase heart rate hence breathing is enhanced. So, it is known as
emergency hormone.
Q10. Name all endocrine glands of our body and write their functions. ( Web Chart)
