Question 1.
What is the importance of DNA copying in reproduction?
Answer.
DNA or deoxy ribonucleic acid is the
genetic material present in the chromosomes. It is responsible for the body
design of an organism. Hence, DNA copying is very important for reproduction.
During reproduction, additional copies of DNA are made so that each new
daughter cell formed has its own DNA. However, during DNA copying, some minor
alterations occur. This results in bringing variations in the long run.
Question 2.
Why is variation beneficial to the species
but not necessarily for the individual?
Answer.
Organisms are normally adapted to live in a
particular kind of niche. In case of alteration in the ecological condition of
that niche, the organism would not be able to survive. Only the variants of
the organisms resistant to changes would survive and grow further. Thus,
variation is beneficial but not necessarily for the individual.
Question 3.
Why is DNA copying an essential part of the
process of reproduction?
Answer.
DNA copying is essential for inheritance of
features from parents to the next generation.
Question 4.
Can you think of reasons why more complex
organisms cannot give rise to new individuals through regeneration?
Answer.
(a) The body
of complex organisms consist of several organ systems which perform
specific functions.
(b) Regeneration is carried out by specialised cells which are not present
in complex organisms.
Question 5.
How does binary fission differ from
multiple fission?
| Binary fission | Multiple fission |
| 1. In this process of reproduction, the cytoplasm of a parent cell divides equally along with the division of nucleus to form two daughter cells. |
1. In this process of reproduction, many daughter cells are formed by the division of a parent cell.
|
| 2. Amoeba and bacteria divide by this process. |
2. Plasmodium divides by this process.
|
Question 6.
Why is vegetative propagation practised for
growing some types of plants?
Answer.
Vegetative propagation is the only method
of reproduction of such plants which do not form viable seeds. It allows the
plant to grow quickly. It takes less time to produce fruits or other
beneficial plant produce.
Question 7.
How is the process of pollination different
from fertilisation?
Answer.
Pollination is the physical process of
transfer of pollen grains from anther to the stigma of the same flower or
another flower of the same species whereas fertilisation is a biological
process in which fusion of male and female gametes takes place.
Question 8.
What is the role of the seminal vesicles
and the prostate gland?
Answer.
The prostate gland makes the medium of
semen alkaline as sperms require an alkaline medium to thrive. The seminal
vesicle adds fluid content to the semen.
Question 9.
What are the changes seen in girls at the
time of puberty?
Answer.
Some of the changes seen in girls at the
time of puberty are:
- The breasts enlarge in size.
- The hips accumulate fat.
- Hairs’grow in the armpits and pubic area.
- The voice becomes thin.
- Girls begin to menstruate.
Question 10.
How does the embryo get nourishment inside
the mother’s body?
Answer.
The embryo gets nourishment through
placenta. It is a cluster of tissues embedded in the uterine wall of the
mother’s body.
Question 11.
If a woman is using a copper-T, will it
help in protecting her from sexually transmitted disease?
Answer.
No, because the copper-T just hampers the
process of implantation of embryo in the uterine wall but not provides
protection against sexually transmitted diseases.
Question 12.
How will an organism be benefited if it
reproduces through spores?
Answer.
There are several advantages if the
organism reproduces by spares:
- There are large numbers of spores formed from one sporangium.
- The spores can remain in dormant state till the favourable conditions are available.
- The spores have thick covering called cyst which helps them to survive in unfavourable conditions.
- The spores are very light and can spread easily through water, air or through the animals.
Chapter End Questions
Question 1.
Asexual reproduction takes place through
budding in
(a) amoeba
(b) yeast
(c) plasmodium
(d) leishmania
Answer.
(b) yeast
Question 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
Question 3.
The anthers contains
(a) sepals
(b) ovules
(c) carpel
(d) pollen
grains
Answer.
(d) pollen
grains
Question 4.
What are the advantages of sexual
reproduction over asexual reproduction?
Answer.
(a) Sexual
reproduction provides opportunity – for new recombination of genes thus causes
genetic variations, which is not applicable to asexual reproduction.
(b) Sexual
reproduction plays an important role in evolution of new species but the
asexual reproduction does not.
Question 5.
What are the functions performed by the
testis in human beings?
Answer.
(a) They form
sperms from the germinal cells present in the seminiferous tubules.
(b) The
hormone testosterone secreted by the Leydig cells induces secondary sexual
characters in male.
Question 6.
Why does menstruation occur?
Answer.
In every month as one of the ovaries
releases ovum and tfie uterine wall thickens and prepares itself for receiving
the developing zygote. When the egg is not fertilised, the level of
progesterone starts decreasing, due to which nourishment to the endometrium is
stopped. As a result, the lining of uterine wall slowly breaks and the
discharge of unfertilised egg along with ruptured endometrium and mucus causes
menstruation in a human female.
Question 7.
Draw a labeled diagram of the longitudinal
section of a flower.
Answer.
Question 8.
What are the different methods of
contraception?
Answer.
Methods of Contraception
- Barrier Methods: Physical devices which prevent the entry of sperms into the female reproductive tract come under barrier methods. Condoms, diaphragms and cervical caps can be used as barrier method.
- Chemical Methods: In these methods, specific drugs are used by the females to avoid pregnancy. These drugs change the hormonal balance of the body so that eggs are not released and fertilisation does not occur. These drugs are taken orally as pills, and therefore, called Oral Contraceptives (OCs).
- IUCDs (Intra Uterine Contraceptive Devices): Lippe’s loop or copper-T are contraceptive devices which are placed inside the uterus to prevent implantation of the embryo.
-
Surgical Methods: Vasectomy in males and tubectomy in females are surgical methods of
population control.
- In males, a small portion of the vas deferens is surgically removed and then cut-ends are tied to prevent the transfer of sperm. This is called vasectomy.
- In females, a small portion of the fallopian tube is surgically removed and the cut-ends are tied to prevent the passage of egg in the uterus. This is called tubectomy.
Question 9.
How are the modes for reproduction
different in unicellular and multicellular organisms?
Answer.
The unicellular organisms reproduce
generally by asexual reproduction like budding, binary and multiple fissions.
However, some unicellular forms also exhibit primitive types of sexual
reproduction like conjugation found in some types of bacteria.
The multicellular organisms have a complex
body structure and reproduce sexually by the distinct sexual body parts.
However, some lower multicellular organisms such as hydra reproduces sexually
in poor feeding conditions.
Question 10.
How does reproduction help in providing
stability to population of species?
Answer.
Every species has to struggle for its
existence. A large number of the population of a particular species is removed
by the predators or by the unfavourable environmental conditions. Reproduction
is the only way to replenish the lost section of the population. If the
organisms of species do not reproduce, their species will foil to exist.
Question 11.
What could be the reasons for adopting
contraceptive methods?
Answer.
Contraceptive methods are adopted to:
(a) prevent
unwanted conception
(b) have
sufficient gap between the successive births.