1.
What is the importance of DNA copying in reproduction?
Answer:
DNA – Deoxyribonucleic
acid is the genetic material that is present in the cells of all organisms. DNA
carries genetic information from one generation to the other and this helps in
producing organisms of its own types. DNA copying is must for inheriting the traits
from the parents. Any variations in DNA copying will give rise to origin of new
species.
2. Why
is the variation beneficial to the species but not necessarily for the
individual?
Answer:
The reason why the
variation is beneficial to the species than individuals is because
sometimes the climatic
changes have a drastic effect on the species which makes their survival
difficult. For examples, if the temperature of the water body increases, then
are might be certain species of microorganisms which might die. This may result
in disturbance in the environment. So, variation is beneficial to species and
not for the individuals.
1. How
does binary fission differ from multiple fission?
Solution:
When a single cell
divides into two equal halves, it is known as binary fission. Bacteria and
amoeba are the examples of binary fission.
When a single cell
divides into multiple daughter cells at the same time, it is
known as multiple
fission. Algae and sporozoans are the examples of multiple
fission.
2. How
will an organism be benefited if it reproduces through spores?
Solution:
Following are the ways
through which an organism will be benefited if it reproduces through spores:
· Number
of spores produced in one sporangium would be large.
· In
order to avoid competition at one place, spores can be distributed to faraway
places with the help of
air.
· In
order to prevent dehydration under unfavorable conditions, the spores are
covered by thick walls.
3. Can
you think of reasons why more complex organisms cannot give rise to new individuals
through regeneration?
Solution:
Organisms at higher
complex levels cannot give rise to new individuals through
regeneration because
they have organization of their organs system at different levels. All these
organ systems are interconnected and work in full coordination. They can regenerate
few of their lost body parts like skin, blood, muscles, etc. but can’t give
rise to new individuals.
4. Why
is vegetative propagation practiced for growing some types of plants?
Solution:
Following are the
advantages of practicing vegetative propagation for growing some types of
plants:
· Crops
like orange, banana, pineapple do not have viable seeds, so
vegetative propagation
can be used.
· It is
a rapid, cheap and easier method to grow crops.
· It can
be used in places where seed germination fails.
· A good
quality of variety can be preserved.
5. Why
is DNA copying an essential part of the process of reproduction?
Solution:
DNA copying is an
essential part of the process of reproduction because it carries the genetic
information from the parents to offspring. A copy of DNA is produced through some
chemical reactions resulting in two copies of DNA. Along with the additional cellular
structure, DNA copying also takes place which is then followed by cell division
into two cells.
1. How
is the process of pollination different from fertilization?
Solution:
Pollination is defined
as the process of transfer of pollens from anther to stigma. The process takes
place with the help of pollinators like air, water and some insects. Fertilization
is defined as the fusion of male and female gametes. It takes place in the ovule
and leads to the formation of zygote.
2.
What is the role of the seminal vesicles and the prostate gland?
Solution:
Lubrication of sperms
and providing of a fluid medium for the easy transportation of sperms takes
place with the help of secretions from the seminal vesicles and the prostate gland.
These secretions also provide nutrients in the form of fructose, calcium and
some enzymes.
3.
What are the changes seen in girls at the time of puberty?
Solution:
Following are the
changes seen in girls at the time of puberty:
· In
genital area, hair growth appears.
· Hair
growth in other areas like underarms, face, hands and legs.
· The
size of uterus and ovary increases.
· The
size of the breast increases followed by darkening of the nipple skin that
are present at the tip
of the breast.
· Beginning
of menstrual cycle.
· Appearance
of pimples, as the oil secretion is more from the skin.
4. How does the embryo get nourishment inside
the mother’s body?
Solution:
The lining of the
uterus thickens after fertilization. The blood flow is good so as to
nourish the growing
embryo. Placenta is a special tissue which is embedded in the uterine wall and
helps the embryo get the nourishment from the mother’s tissue. Placenta has villi
on the embryo side and blood space on the mother’s side. This spacing provides
a large area between the mother and the embryo and also for the waste removal.
5. If
a woman is using a Copper-T, will it help in protecting her from sexually
transmitted
diseases?
Solution:
No, because usage of
copper-T cannot stop the contact of body fluids. Hence, it cannot protect her
from getting sexually transmitted diseases.
QUESTIONS
1. Asexual reproduction takes place through budding in
(a) Amoeba
(b) Yeast
(c) Plasmodium
(d) Leishmania
Answer:
(b)
Yeast
Yeast
is an example for asexual reproduction taking place through budding. A small protuberance
is produced on the parent cell that grows in full size forming a bud. In the parent
cell, the daughter nucleus splits and migrates to the daughter cell. By forming
a constriction, the bud detaches from the mother’s body at the base. This
process of budding continues to form a chain of bud cells. The mother cell is
smaller than the daughter cell.
2. Which of the following is not a part of the female reproductive
system in human beings?
(a) Ovary
(b) Uterus
(c) Vas deferens
(d) Fallopian tube
Answer:
(c) Vas deferens
Vas
deferens is a part of male reproductive system. It is a long, muscular tube
travelling from the epididymis into the pelvic cavity. It is behind the
bladder. Its function is to transport the mature sperm to the urethra. It also
carries urine to the outside of the body.
3. The anther contains
(a) Sepals
(b) Ovules
(c) Pistil
(d) Pollen grains
Answer:
(d)
Pollen grains.
Pollen
grains are the microscopic particles that occurs in the pollen giving rise to
male gametophyte of a seed plant.
4. What are the advantages of sexual reproduction over asexual
reproduction?
Answer:
Following
are the advantages of sexual reproduction:
·
The
offspring has the characters of both the parent.
·
The
survival of the species is ensured as there are more variations.
·
The
offspring can easily adapt to environmental changes.
·
It
also improves the health of humans.
5. What are the functions performed by the testis in human beings?
Answer:
Following
are the functions performed by the testis in human beings:
·
Apart
from the production of sperms, it also produces the male hormone
known as androgens.
·
They
also produce hormone called testosterone, which is responsible for
secondary sexual characters in boys.
6. Why does menstruation occurs?
Answer:
Menstruation
is the normal bleeding of the vaginal line which starts between puberty and lasts
till menopause. During this period, the body prepares itself for the pregnancy.
Every
month an egg is released from one of the ovaries at the same time where the
uterus prepares itself for fertilized egg. The inner lining of the uterus gets
thickened and is supplied with sufficient amount of blood for the embryo. Since
there is no interaction between the egg and the sperms, the fertilization of
egg doesn’t takes place. So when the egg doesn’t fertilized, the uterus lining
breaks down slowly resulting in menstruation.
7. Draw a labelled diagram of the longitudinal section of a
flower.
Answer:
8. What are the different methods of contraception?
Answer:
Following
are the different methods of contraception:
·
Natural
method: In this method, the main focus is to avoid the meeting of sperms and
ovum. This can be achieved by avoiding the mating from 10th to 17th day of the
menstrual cycle. During this period, there are high chances of fertilization as
the ovulation is expected.
· Barrier method: In this method, the meeting of sperms and ovum is avoided by using a barrier. These barriers are available for males as well as for females. Condoms for both male and female, diaphragms for female, cervical cap and contraceptive sponge for females.
·
Oral
contraceptives: In this methods, pills are taken orally. These pills
contain small portion of hormones that block the eggs
so that the fertilization
doesn’t takes place.
·
Implants
and surgical method: In this method, contraceptive devices like
copper-T or a loop can be used to block the meeting of
sperms and ovum. In
surgical method, the fallopian tubes are blocked in
females to stop flow of
eggs and vas deference is blocked in men to stop the
flow sperms.
9. How are the modes for reproduction different in unicellular and
multicellular organisms?
Answer:
The
different modes of reproduction in unicellular organisms are fission, budding
etc. Here, the cell divides into two daughter cells and this process of cell
division continues. Whereas, in multicellular organisms there is a different
organ system for reproduction. The different modes of reproduction in
multicellular organisms are vegetative propagation, spore formation, etc.
In
more complex organisms like humans and animals, the reproduction is through sexual
reproduction.
10. How does reproduction help in providing stability to
populations of species?
Answer:
Reproduction
is the process of producing the same kind of species by the existing
species.
This is done so as to maintain the population of that species and also to take forward
their species to next generations. Stability is maintained by keep a check of
rate of births and rate of deaths.
11. What could be the reason for adopting contraceptive methods?
Answer:
Following
are the reasons for adopting contraceptive methods:
·
To
control population
·
To
avoid unplanned pregnancy
·
To
avoid transfer of sexually transmitted diseases
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