NCERT Solutions for Class 10 Science Chapter 8 - “How Do Organisms Reproduce?” by Farrukh
Answer The Following Question.
NCERT Solutions for Class 10 Science Chapter 8 Intext
Questions
1. What is the importance of DNA copying in reproduction?
Answer:
DNA (Deoxyribonucleic corrosive) is the hereditary
material found in the chromosomes, which are available in the core of a cell.
The DNA is the data site for making proteins and every particular sort of
protein prompts a particular kind of body plan.
Accordingly, the DNA particle decides the body plan of a person. Thusly, it
very well may be presumed that the DNA gets moved from guardians to offsprings
and makes them seem to be comparable.
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2. Why is variation beneficial to the species but not
necessarily for the individual?
Answer:
Varieties are valuable for the endurance of species in
changed climate circumstances. If a populace of recreating life form were fit
to a specific specialty and on the off chance that the specialty is radically
modified the populace could be cleared out. In any case, a few varieties are
available a few animal groups will get by. In this manner, variety is helpful
to species yet not the person.
3. How does binary fission differ from multiple fissions?
Answer:
Difference between binary
fission and multiple fission :
|
Binary fission |
Multiple fission |
|
Splitting Of
unicellular organisms like amoeba into nvo equal halves during cell division
is termed binary fission. |
Division
Of single-celled organisms such as malarial parasites into many daughter
cells simultaneously is termed multiple fission. |
Answer:
The spores are
covered by thick walls that protect them until they come into contact with
suitable moist surface and can begin to grow.
Answer:
Basic creatures,
for example, Hydra and Planaria are equipped to deliver new people through
recovery. The recovery course includes the development of new organic entities
from its body parts. Basic creatures can use this technique for proliferation
as their whole body is made of a comparative sort of cells in which any piece
of their body can be shaped by development and advancement. Notwithstanding,
complex life forms have an organ-framework level of association. All the organ
frameworks of their body cooperate as an interconnected unit. They can recover
their lost body parts like skin, muscles, blood, and so on. In any case, they
can't bring about new people through recovery.
Answer:
(i) Plants raised
by vegetative propagation can bear flower and fruits earlier than those
produced from seeds.
(ii) Such methods
also make possible the propagation of plants such as banana, orange, rose and
jasmine that have lost the capacity to produce seeds.
(iii) All plants
produced by this method are genetically similar enough to the parent plant to
have its all characteristics.
Answer:
DNA contains
information for the inheritance of features from parents to next generation.
DNA present in the nucleus of cells are the information source for making proteins.
If information is different, different proteins will be made which leads to
altered body design.
8. How is the process of pollination different from
fertilization?
Answer:
The distinction between
pollination and fertilization:
|
Pollination |
Fertilisation |
|
Pollination refers to
the process of transfer of pollen grains from anther
to stigma of flower. |
Fertilisation refers
to fusion of male and female gamete
to form a zygote. |
Answer:
Secretions of
seminal vesicles and prostate gland provide fluid medium to sperm to move and
also provide nutrition to them.
10. What are the changes seen in girls at the time of puberty?
Answer:
During puberty
breast size begins to increase with darkening of the skin of the nipples at the
tip of breasts. Also, girls begin to menstruate at around this time.
11. How does the embryo get nourishment inside the mother’s
body?
Answer:
The undeveloped
organism creates inside the mother's body for around nine months. Inside the
uterus, the external tissue encompassing the undeveloped organism creates
finger-like projections called villi. These villi are encircled by uterine
tissue and maternal blood. They give a huge surface region to trade of oxygen
and supplements. Likewise, there is an exceptional tissue called placenta,
which is implanted in the uterine wall. The incipient organism gets the oxygen
and supplements from the mother's blood by means of the placenta. The waste
materials created by the undeveloped organism are likewise taken out through
the placenta.
12. If a woman is using a Copper-T, will it help in
protecting her from sexually transmitted diseases?
Answer:
Copper-T cannot
protect the woman from acquiring sexually transmitted diseases. It will protect
her from only unwanted pregnancy.
13. Asexual reproduction takes place through budding in
(a) Amoeba
(b) Yeast
(c) Plasmodium
(d) Leishmania.
Answer: (b)
Yeast
14. Which of the following is not a part of female
reproductive system in human beings?
(a) Ovary
(b) Uterus
(c) Vas deferens
(d) Fallopian tube
Answer: (c)
Vas deferens
15. The anther contains
(a) Sepals
(b) Ovules
(c) Carpel
(d) Pollen grains.
Answer: (d)
Pollen grains.
16. What are the advantages of sexual reproduction over
asexual reproduction?
Answer:
Sexual
reproduction leads to variation due to the recombination of genetic material DNA.
These variations are essential for survival of species. On the contrary,
asexual reproduction does not bring about variations.
17. What are the functions performed by the
testis in human beings?
Answer:
In human beings,
testes perform dual function:
(i) Production of
sperms
(ii) Secretion of
male hormone testosterone.
18. Why does menstruation occurs.
Answer:
When in human
female if the egg is not fertilized, it lives for about one day. Since the
ovary releases one egg every month, the uterus also prepares itself every month
to receive a fertilized egg. Thus, its lining becomes thick and spongy. This
would be required for nourishing the embryo if had fertilized. However, this
lining is not required any longer. So, the lining slowly breaks and comes out
through the vagina as blood and mucous. This cycle takes roughly every month
and is known as menstruation.
19. Draw a labeled diagram of the longitudinal section of a
flower.
Answer:
20. What are the different methods of contraception?
Answer:
The contraceptive
methods can be broadly divided into the following types:
· Natural method— It involves avoiding the
chances of meeting of sperms and ovum. In this method, the sexual act is
avoided from day 10th to the 17th of the menstrual cycle because during this
period, ovulation is expected and therefore, the chances of fertilization are
very high.
· Barrier method In this method, the
fertilization of ovum and sperm is prevented with the help of barriers.
Barriers are available for both males and females. Condoms are barriers made of
thin rubber that are used to cover penis in males and the vagina in females.
· Oral contraceptives In this method,
tablets or drugs are taken orally. These contain small doses of hormones that
prevent the release of eggs and thus fertilization cannot occur.
· Implants and surgical methods
Contraceptive devices such as the loop or Copper-T are placed in uterus to
prevent pregnancy.
Note:
Some surgical methods can also be used to block the
gamete transfer. It includes the blocking of vas deferens to prevent the
transfer of sperms known as vasectomy. Similarly, fallopian tubes of the female
can be blocked so that the egg will not reach the uterus known as tubectomy.
21. How are the modes of reproduction different in
unicellular and multicellular organism?
Answer:
In unicellular organisms,
cell division, or fusion leads to the creation of new individuals. In
multicellular organisms with simple body organization budding, fragmentation
may work but in complex multicellular organisms only sexual reproduction takes
place.
22. How does reproduction help in providing stability to
populations of species?
Answer:
The consistency of
DNA copying during reproduction is important for the maintenance of body design
features that allow the organism to use a particular niche. Reproduction is,
therefore, linked to the stability to populations of species.
23. What could be the reasons for adopting contraceptive
methods?
Answer:
The sexual act
always has the potential to lead to pregnancy. Pregnancy will make major
demands on the body and the mind of the woman and if she is not ready for it,
her health will adversely affected. Therefore, adopting contraceptive methods
are essential. Some contraceptive methods like condom also prevent spread of
STDs and lethal diseases like HIV-AIDS.
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