Page: 128
1. What is the importance of DNA copying in reproduction?
Answer:
· It maintains the characteristics of species.
· It maintains the continuity of life.
· Characters of organisms are transmitted to their progeny.
· It produces variations in organisms.
2. Why is variation beneficial to the species but not
necessarily for the individual?
Answer:
Consistent DNA copying maintains body design. It helps the
organism to use a particular niche.
However, niches can be changed due to many reasons. If a
niche is drastically altered, the population not suited to that niche is wiped
out. The organisms which have variations to survive can reproduce under the
varied conditions. Hence variation is beneficial to species, but not to individuals.
Page: 133
1. How does binary fission differ from multiple fission?
Answer:
|
Binary fission |
Multiple fission |
|
Parent cell divides into 2
daughter cells. |
Parent cell divides into many
daughter cells. |
|
No cyst formation. |
A cyst is formed. |
|
It generally occurs in
favourable conditions. |
It occurs in unfavourable
conditions too. |
2. How will an organism be benefited if it reproduces through
spores?
Answer:
Spores are surrounded by a thick layer to protect them in
adverse conditions. Under favourable condition, these spores start to grow
again.
3. Can you think of reasons why more complex organisms cannot
give rise to new individuals through regeneration?
Answer:
Complex multicellular organisms have a very high degree of
organisation and differentiation in their body. So, they cannot be reproduced
from their cut body parts by the process of regeneration.
E.g., the cells in a finger cannot produce organs such as
brain, heart, eye, stomach, intestine etc. So a complete organism will not be
developed from finger.
4. Why is vegetative propagation practised for growing some
types of plants?
Answer:
It is practiced for growing plants which usually do not produce
seeds or produce non-viable seeds.
5. Why is DNA copying an essential part of the process of
reproduction?
Answer:
DNA is the information source for making proteins. If the
information is changed, different proteins will be made. It leads to change in
body designs. Therefore, creation of a DNA copy is the basic event in
reproduction.
Page: 140
1. How is the process of pollination different from
fertilisation?
Answer:
Pollination is
the transfer of pollen grains from the anther of to the stigma of a carpel.
Fertilisation
is the fusion of male gamete present in pollen grain with the female gamete
present in ovule.
2. What is the role of seminal vesicles and the prostate
gland?
Answer:
· Seminal vesicle and prostate gland secrete fluids which
form a part of the semen. It acts as a medium for the movement of sperms.
· This fluid provides nutrition to sperms in the form of
fructose, calcium & some enzymes. It also protects the sperms from the
acids present in the urethra.
3. What are the changes seen in girls at the time of puberty?
Answer:
·
Hairs under armpits and pubic region.
· Mammary glands develop and enlarge.
· The hips broaden.
· Extra fat is deposited in hips and thighs.
· Development of fallopian tubes, uterus and vagina.
· Menstrual cycle and Menstruation.
· Feelings and sexual drives.
4. How does the embryo get nourishment inside the mother’s
body?
Answer:
The embryo gets nutrition from the mother’s blood through placenta.
Placenta contains villi. It provides a large surface area for the transfer of
glucose, oxygen and other substances from the mother to the embryo.
5. A woman is using a copper-T. Will it help in protecting
her from sexually transmitted diseases?
Answer:
Copper-T prevents conception but cannot prevent sexually transmitted diseases.