Extra Questions
8. What are the different methods of contraception?
Full Chapter In One Video
Questions Page no: 128
1. What is the importance of DNA copying in reproduction?
Solution:
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 a must for inheriting the traits from 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?
Solution:
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 there 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.
Questions Page no: 128
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 a few of their lost body parts like skin,
blood, muscles, etc. but can’t give rise to new individuals.
4. Why is vegetative propagation practised for growing some types of plants?
Solution:
Following are the advantages of practising 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.
Questions Page No: 140
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 is 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 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.
Exercises Page no: 141
1. Asexual reproduction takes place through budding in
(a) Amoeba (b) Yeast (c) Plasmodium (d) Leishmania Solution: (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
Solution: (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
Solution: (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?
Solution:
Following are the advantages of sexual reproduction: The offspring has the
characters of both the parents. 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?
Solution:
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? Solution:
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 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 get
fertilized, the uterus lining breaks down slowly resulting in menstruation.
7. Draw a labelled diagram of the longitudinal section of a flower.
Solution:
Solution:
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 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 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 of sperms.
9. How are the modes for reproduction different in unicellular and
multicellular organisms? Solution:
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?
Solution:
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? Solution:
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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