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How Do Organisms Reproduce
Q. What is reproduction?
Ans. Reproduction is a biological process through which a new organism
from an existing organism of the same species is produced.
Q. What is the need of reproduction for an organism?
Ans. Reproduction is not essential for a single organism so it is not
categorized as an essential life process but it is very essential for a species
to survive on the earth and maintain their continuity. Thus reproduction
helps in providing stability to populations of species.
Q. What are the types of reproduction?
Ans.
Q. What does Asexual Reproduction mean?
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Ans. A type of reproduction in which a new organism is produced from a
single parent without the involvement of sex cells, is called an Asexual
Reproduction.
Some of the examples of Asexual Reproduction are :-
Binary fission in Amoeba, Budding in Hydra, Spore formation in
Rhizopus, Regeneration in Planaria, Fragmentation in Spirogyra and
Vegetative Propagation in some plants.
Q. What does Sexual Reproduction mean?
Ans. A type of reproduction in which a new organism is produced from two
parents with the involvement of sex cells, is called a Sexual Reproduction.
Examples:- Humans, Fish, Hens, Flowering plants and many more use
sexual reproduction.
Q. What are the differences between Asexual Reproduction and Sexual
Reproduction?
Ans.
Asexual Reproduction
Sexual Reproduction
Single parents are involved.
Two parents are involved.
No sex cells are involved.
Sex cells are involved.
Produced organism is identical to
the parent.
Produced organism is not identical
to the parent.
Least variation is seen.
Most variation is seen.
Less energy is required.
High amount of energy is required.
It is a fast process.
It is a slow process.
In this, only mitosis is involved.
In this, meiosis and mitosis both are
involved.
Examples:- Amoeba, Hydra,
Rhizopus, etc.
Examples:- Humans, Fish, Hens,
Flowering plants, etc.
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Q. What is mitosis?
Ans. Mitosis is a process of cell division in which two identical daughters
are produced and the number of chromosomes are equal to their parent
cell. This process is done by all cells except sex cells.
Q. What is meiosis?
Ans. Meiosis is a process of cell division in which four non identical
daughters are produced and the number of chromosomes are halved to
their parent cell. This process is done by only sex cells.
Q. What are the methods of asexual reproduction?
Ans. There are mainly six types of asexual reproduction and they are:-
1. Fission
2. Budding
3. Spore formation
4. Regeneration
5. Fragmentation
6. Vegetative propagation
Q. What is fission?
Ans. Fission is a type of asexual reproduction in which a unicellular
organism splits to form two or more new identical organisms of the same
species.
There are two types of fission:-
1. Binary fission:- In binary fission, the parent organism splits to form
two new identical organisms of the same species.
Example:- Amoeba, Paramecium, Leishmania and bacteria use this
method for reproduction.
2. Multiple Fission:- In binary fission, the parent organism splits to form
many new identical organisms of the same species at the same time.
Example:- Plasmodium(Protozoan)
Q. Explain binary fission in Amoeba?
Ans. Amoeba(protozoa) is a unicellular and it uses binary fission for the
reproduction. This happens as follows :
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When the Amoeba cell has reached its maximum size of growth, then first
the nucleus of Amoeba lengthens and divides into two parts. After that the
cytoplasm of Amoeba divides into two parts, one part around each nucleus.
In this way, one parent Amoeba divides in any plane to form two smaller
Amoebae (called daughter Amoebae). The reproduction in Amoeba by
binary fission is shown below:-
Q. Explain binary fission in Leishmania?
Ans. Leishmania(Protozoan) is a unicellular organism. It is a parasite which
causes the disease known as kala-azar (or black fever). Kala-azar is also
known as leishmaniasis. Leishmania has a greater degree of organisation
in its body, having a whip-like structure called flagellum at its one end.
Leishmania reproduces by the process of binary fission. In Leishmania, the
splitting of the parent cell during binary fission takes place in a definite
plane (longitudinally) with respect to flagellum at its end.
Q. Explain multiple fission in Plasmodium?
Ans. Plasmodium(protozoan) is a unicellular organism which reproduces
by the asexual method of multiple fission. About 1000 daughter cells are
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produced by the multiple fission of one Plasmodium cell. Plasmodium is the
malarial parasite which produces malaria disease in human beings. In
Plasmodium multiple fission happens as follows:-
A cyst or protective wall is formed around the single-celled Plasmodium.
Inside the cyst, the nucleus of the cell splits several times to form many
smaller nuclei called daughter nuclei. Little bits of cytoplasm collect around
each daughter nuclei and thin membranes are formed around them. In this
way, many new daughter cells are formed from a single parent cell within
the cyst. When the favourable conditions arrive, the cyst breaks open and
the many daughter cells present in it are released, each forming a new
organism.
Q. What is budding?
Ans. Budding is an asexual method of reproduction. In budding, a small
part of the body of the parent organism grows out as a ‘bud’ which then
detaches and becomes a new organism. The asexual reproduction by
budding is observed in Hydra and yeast. This is described below:-
Q. What is spore formation?
Ans. Spore formation is the asexual method of reproduction. The
reproduction by spore formation takes place in some plants.
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In spore formation, the parent plant produces hundreds of microscopic
reproductive units called ‘spores’.The spores are covered by thick walls
that protect them until they come into contact with another moist surface
and can begin to grow. When the spore case of the plant bursts, then the
spores spread into air. When these air-borne spores land on food (or soil)
under favourable conditions (like damp and warm conditions), they
germinate and produce new plants.
Most of the fungi (like Rhizopus, Mucor, etc.), bacteria and non-flowering
plants such as ferns and mosses reproduce by the method of spore
formation.
The common bread mould is a fungus plant whose scientific name is
Rhizopus. The Rhizopus reproduces by the method of spore formation. The
thread-like structures of Rhizopus are the hyphae on the other hand, the
tiny blob-on-a-stick structures are sporangia , which contain cells, or
spores, that can eventually develop into new Rhizopus individuals
This is described below:-
Q. What is regeneration?
Ans. Regeneration is the asexual method of reproduction.In this process a
cutting part of an organism grows into a separate complete organism.
Regeneration is carried out by specialised cells. These cells proliferate
and make large numbers of cells. From this mass of cells, different cells
undergo changes to become various cell types and tissues. These changes
take place in an organised sequence referred to as development. However,
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regeneration is not the same as reproduction, it is like a development or
repairing.
Example:- Planaria and Hydra use this method of reproduction.
Q. What is fragmentation?
Ans. Fragmentation is an asexual method of reproduction. In this process
an organism simply breaks up into smaller pieces upon maturation. These
pieces or fragments grow into new individuals.
Examples:- Spirogyra, Sea anemone etc.
Q. Why the complex multicellular organisms (like mammals) cannot give
rise to complete individuals from their cut body parts through the process of
regeneration or fragmentation.
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Ans. Regeneration or fragmentation can be used to reproduce only those
organisms which have relatively simple body organisation consisting of only
a few specialised cells (or tissues).
Complex multicellular organisms are not simply a random collection of
cells. Specialised
cells are organised as tissues, and tissues are organised into organs,
which then have to be placed at definite positions in the body. In such a
carefully organised situation, cell-by-cell division would be impractical. For
example, a dog is a complex multicellular organism which cannot be
regenerated from its cut body part, say, a cut tail. This is because the cells
present in the cut tail of a dog cannot produce a dog's organ like heart,
brain, lungs, stomach, intestines and limbs, etc, needed for the making of a
complete dog.
Q. Difference between Budding, Regeneration and Fragmentation.
Ans.
Budding
Regeneration
Fragmentation
It is done by unicellular
organisms.
It is something like,
developing one’s lost
part.
In this no lost part is
there and it is done in
multicellular
organisms.
Q. What is Vegetative Propagation?
Ans. Vegetative Propagation is an asexual method of reproduction. This
method is used only by plants. In vegetative propagation, new plants are
obtained from the parts of old plants (like stems, roots and leaves), without
the help of any reproductive organs. There are two types of vegetative
propagation:- (i) Natural and (ii) Artificial(Cutting, Layering and Grafting)
There are many plants especially which do not have seeds such as
banana, orange, rose and jasmine, which parts like the root, stem and
leaves develop into new plants under appropriate conditions.
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Q. What is cutting?
Ans. A small part of a plant which is removed by making a cut with a sharp
knife is called a ‘cutting’.
This method is done for many plants such as :- Money plants, Rose,
Hibiscus, grapes, sugarcane, bananas, etc.
Q. What is layering?
Ans. In this method, a branch of the plant is pulled towards the ground and
a part of it is covered with moist soil leaving the tip of the branch exposed
above the ground. After some time, new roots develop from the part of the
branch buried in the soil. The branch is then cut off from the parent plant.
The part of the branch which has developed roots grows to become a new
plant.
This method is used for jasmine, lemon, guava, strawberry, raspberry, etc.
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Q. What is grafting?
Ans. Grafting is a method in which the cut stems of two different plants
(one with roots and other without roots) are joined together in such a way
that the two stems join and grow as a single plant. This new plant will have
the characteristics of both the original plants.
Apple, peach, apricot and pear trees are often grafted.
Q. What are the advantages of reproduction by vegetative propagation?
Ans. The advantages of reproduction by vegetative propagation are :-
1. Plants raised by vegetative propagation can bear flowers and fruits
earlier than those produced from seeds.
2. Plants raised by vegetative propagation are genetically similar and
have exact properties of the parent plants.
3. This method also makes possible the propagation of plants such as
banana, orange, rose and jasmine that have lost the capacity to
produce seeds.
4. Plants are produced very fast as compared to the plants produced by
sexual methods.
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5. The plants grown by vegetative propagation usually need less
attention in their early years than the plants grown from seeds.
Q. What is tissue culture?
Ans. In tissue culture, new plants are grown by removing tissue or
separating cells from the growing tip of a plant. The cells are then placed in
an artificial medium where they divide rapidly to form a small group of cells
or callus. The callus is transferred to another medium containing hormones
for growth and differentiation. The plantlets are then placed in the soil so
that they can grow into mature plants. Using tissue culture, many plants
can be grown from one parent in disease-free conditions. This technique is
commonly used for ornamental plants
Q. How does binary fission differ from multiple fission?
Ans.
Binary fission
Multiple fission
From a parent unicellular organism
two daughter cells are produced.
From a parent unicellular organism
multiple daughter cells are
produced.
Single division takes place.
Multiple divisions take place.
Both nucleus and cytoplasm divide
simultaneously.
Nucleus division takes place first
and then cytoplasm.
It is seen in Amoeba and
Paramecium.
It is seen in Plasmodium.
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Q. How will an organism be benefited if it reproduces through spores?
Ans. An organism be benefited in many ways if it reproduces through
spores and they are:-
1. This method of reproduction is very fast
2. At one time many organisms are produced.
3. Spores bear thick resistant covering to enable them to survive even in
unfavourable conditions.
4. Spores being small and light get easily dispersed through wind water
and animals. Thus its dispersal becomes easier.
5. Since the spores are extremely light weight, they can travel great
distances and therefore dispersed in a large area and hence reduce
the competition among the offspring for nutrition.
Q. Can you think of reasons why more complex organisms cannot give
rise to new individuals through regeneration?
Ans. More complex organisms are not just a bulk of cells. They have
specialised cells to make specialised tissue and tissues are organised into
organs, which then have to be placed at definite positions in the body. In
such a carefully organised situation, cell-by-cell division would be
impractical.
Q. Why is vegetative propagation practised for growing some types of
plants?
Ans. There are many reasons for vegetative propagation is practised for
growing some types of plants, for example:-
1. This method makes possible the propagation of the plants that have
lost the capacity to produce seeds.
2. To obtain fruits or flowers in less time.
3. To obtain identical fruits or flowers to the parent plants.
Q. Do organisms create exact copies of themselves in asexual
reproduction?
Ans. Yes, asexual reproduction usually results in the production of exact
copies of offspring and hence called clones of the parent cell. The only
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genetic variation arises as a result of occasional inaccuracies in DNA
replication (or DNA copying) at the time of cell division.
Q. What is DNA?
Ans. DNA(Deoxyribo Nucleic Acid) is the material which carries genetic
information from the parents to the offspring, such as body design
(blueprints of the body), the information source for making proteins.
and many more which are essential for the organism to survive.
Q. What is the importance of DNA copying in reproduction?
OR
Q. Why is DNA copying an essential part of the process of reproduction?
Ans. DNA copying or DNA replication means making a duplicate copy from
an existing DNA. Cells use chemical reactions to build copies of their DNA.
It is a basic event in any reproduction.
DNA copying is very essential in reproduction for the following reasons:-
1. New organisms look similar to their parents only because of DNA
replication, which contains the blueprints of the body design of the
parent organism.
2. New organisms are able to survive in the parent’s environment
because they contain the same DNA, because of DNA replication.
3. If the copying of DNA does not occur during reproduction then there
is a very little chance of the survival of the new produced organism.
Q. What does variation mean?
Ans. Replication of DNA is a biochemical reaction and no bio-chemical
reaction is absolutely reliable so there is a chance of some errors which
changes the contained information in DNA. If the information is changed,
different proteins will be made. Different proteins will eventually lead to
altered body designs, functions etc, which is known as variation.
Q. Why is variation beneficial to the species but not necessarily for the
individual?
Ans. If a population of reproducing organisms are suited to a particular
environment and no variation occurs during reproduction then the new
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produced organism will also survive in that environment. So it is not
necessarily for the individual.
But if the environments were drastically altered, the population could
be wiped out. However, if some variations were to be present in a few
individuals in these populations, there would be some chance for them to
survive. Variation is thus useful for the survival of species over time.
Q. A hibiscus plant can be reproduced by both sexually and asexually
methods, then which methods is best for a planter?
Ans. It depends upon the will of the planter. If he wishes to obtain the exact
copy of the preexisting hibiscus plant then he will select the plants
reproduced by asexual method and if wants some variation then he will
select the plants reproduced by sexual method.
Q. What are gametes?
Ans. The special cells which have half the number of chromosomes
involved in sexual reproduction are called gametes also known as sex cells
or germ cells.
Q. What is sexual reproduction?
Ans. A type of reproduction in which a new organism is produced from two
parents with the involvement of sex cells(gametes), is called a Sexual
Reproduction.
Examples:- Humans, Fish, Hens, Flowering plants and many more use
sexual reproduction.
Q. What are the basic processes that take place during sexual
reproduction?
Ans. In sexual reproduction, a male gamete fuses with a female gamete to
form a new cell called ‘zygote’. This zygote then grows and develops into a
new organism in due course of time.
Q. Which types of plants reproduce by sexual method?
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Ans. The flowering plants (also known as angiosperm) reproduce by
‘sexual reproduction’ method. The sex organs (or reproductive organs) of
the plants are in its flowers.
Q. What are the types of flower with respect to reproduction?
Ans. There are mainly two types of flower with respect to reproduction:-
1. Unisexual:- The flower which contains only one type sex cell(male or
female) Example :- Papaya, Watermelon etc.
2. Bisexual:- The flower which contains both types of sex cells(male and
female) Example:- Hibiscus, mustard etc.
Q. What are the main parts of a flower and write their function?
Ans. The main parts of a flower are:- Sepals, Petals, Stamens and Pistil.
Sepals:- Sepals are the leaf-like green outer covering of a flower. All the
sepals taken together are called ‘calyx’. It protects the petals before a
flower blooms and after blooming it provides support to the petals.
Petals :- Petals are the colorful and fragrant parts of a flower. All the petals
taken together are called ‘corolla’. They help in pollination by attracting
insects.
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Stamen:- Stamen are male sex organs. It consists of two parts : Filament
and Anther. Anther is the part which produces sex cells inside a pollen
grain which is yellowish in color.
Pistil :- Pistil is a female sex organ. It has carpels which consist of three
parts : Ovary, Style and Stigma. The swollen bottom part is the ovary, the
middle elongated part is the style and the terminal part which may be sticky
is the stigma. The ovary contains ovules and each ovule has an egg cell
which is also known as ova.
Q. What is the function of a flower?
Ans. The function of a flower is to make male and female gametes and to
ensure that fertilisation will take place to make new seeds for the
reproduction of plants.
Q. What does pollination mean?
Ans. Transfer of pollen grains from anther to stigma is called pollination.
There are two types of pollination:-
1. Self pollination:- Transfer of pollen grains from an anther of a flower
to stigma of the same flower is called self pollination.
2. Cross pollination:- Transfer of pollen grains from an anther of a flower
to stigma of another flower is called cross pollination.
Q. What are the agents of pollination?
Ans. To transfer pollen grains from anther to stigma, some carrier is
required and they are called agents of pollination, which are air, water and
insects.
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Q. What happens after the pollination?
Ans. After the pollen lands on a suitable stigma, it has to reach the
female germ-cells which are in the ovary. For this, a tube grows
out of the pollen grain and travels through the style to reach the
ovary. This process is called germination of pollen.
Q. What are the steps in sexual reproduction in plants?
Ans. The sexual reproduction in plants takes place in the following steps :
1. The male organ of flower called ‘stamen’ makes the male gametes
(male sex cells) of the plant. These male gametes are present in
pollen grains.
2. The female organ of a flower called ‘pistil’ or ‘carpel’ makes the
female gametes (female sex cells) of the plant.These female gametes
are present in ovules. The female gametes present in ovules are also
called ‘ova’, ‘egg cells’ or just ‘eggs’.
3. The male gametes present in pollen grains fertilise the female
gametes or egg cells present in ovules.
4. The fertilised egg cells grow within ovules and become seeds.
5. The seeds produce new plants on germination (under suitable
conditions of water, warmth, air and light, etc.).
Q. What does fusion mean and what is the site of fusion in flowering
plants?
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Ans. After the germination of pollen on stigma, the male sex cell from
pollen grain travels through the pollen tube and reaches the ovule and then
ovary where egg cells are present. The pollen grain penetrates an egg cell
and enters into the egg cell which is known as fusion.
Ovary is the place where fusion takes place.
Q. What does fertilisation mean?
Ans. Union of a male sex cell and a female sex cell is called fertilisation. It
takes place in embryo sacs in flowering plants.
Q. What happens after the fertilisation in a flower of a plant?
Ans. After the fertilisation a zygote is formed inside the ovule. The zygote
divides several times to form an embryo. The ovule develops a tough coat
and is gradually converted into a seed. The ovary grows rapidly and ripens
to form a fruit. Meanwhile, the petals, sepals, stamens, style and stigma
may shrivel and fall off.
Q. What is germination?
Ans. A seed is the reproductive unit of a plant. The seed contains the
future plant or embryo which develops into a seedling under appropriate
conditions. This process is known as germination.
Q. What is puberty?
Ans. The physical transition or sexual maturation period in humans during
teenage(13-19 years) is called puberty.
Q. What changes take place during puberty in a human?
Ans. There are two types of changes that take place during puberty in
humans:- (i) Common to boys and girls and (ii) Different in boys and girls
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1. Common to boys and girls:- Growing of thick hair in new parts of
the body such as armpits and the genital area between the thighs.
Thinner hair can also appear on legs and arms, as well as on the
face. The skin frequently becomes oily and develops pimples. They
begin to be conscious and aware of their own bodies and those of
others in new ways. They start producing their sex cells.
2. Different in boys and girls:-
a. In girls:- Breast size begins to increase, also, girls begin to
menstruate(Periods) at around this time.
b. In boys:- Boys begin to have new thick hair growth on the face
and their voices begin to crack. Further, the penis occasionally
begins to become enlarged and erect, either in daydreams or at
night.
Q. Why does the body show sexual maturation at the puberty stage?
Ans. Before the puberty stage, the body’s focus is on the body's
development or growth so most of the energy is consumed in this. But at
this stage the rate of development slows down and the most energy is used
for sexual maturation.
Q. How are the changes during puberty linked to the reproduction process?
Ans. The sexual mode of reproduction means that germ-cells from two
individuals have to join together. This can happen by the external release of
germ-cells from the bodies of individuals, as happens in flowering plants.
Or it can happen by two individuals joining their bodies together for internal
transfer of germ-cells for fusion, as happens in many animals. If animals
are to participate in this process of mating, their state of sexual maturity
must be identifiable by other individuals. Many changes during puberty,
such as new hair-growth patterns, are signals that sexual maturation is
taking place, erecting of pennis means it is capable of transferring its germ
cells(sperm), the baby is carried in the mother’s body for a long period, and
will be breast-fed later. So the female reproductive organs and breasts will
need to mature to accommodate these possibilities.
Q. What is sperm?
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Ans. Sperm is a male sex cell of an animal or human. A sperm is about
0.05 mm long. A sperm has a head, a middle piece and a tail. A sperm is a
single cell with nucleus, cytoplasm and cell membrane.
Q. Explain Male Reproductive System.
Ans. The male reproductive system consists of portions which produce the
germ-cells and other portions that deliver the germ-cells to the site of
fertilisation. The formation of germ-cells or sperms and testosterone
hormones takes place in the testes. There are 2 testes in human and they
are located outside the abdominal cavity in the scrotum. They are the
primary reproductive organs in man.
The sperms formed are delivered through the vas deferens which
unites with a tube coming from the urinary bladder. The urethra thus forms
a common passage for both the sperms and urine. Along the path
of the vas deferens, glands like the prostate and the seminal vesicles add
their secretions so that the sperms are now in a fluid, known as semen,
which makes their transport easier and this fluid also provides nutrition. The
sperms are tiny bodies that consist of mainly genetic material and a long
tail that helps them to move towards the female germ-cell.
Q. Why are testes located outside the abdominal cavity?
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Ans. Testes are the site where sperms and hormones are produced and
sperm formation requires a lower temperature than the normal body
temperature, so they are located outside the abdominal cavity in a bag-like
structure called scrotum.
Q. Explain the Female Reproductive System?
Ans. The female germ-cells or eggs are made in the ovaries. Ovaries are
the primary reproductive organs in a woman. They are also responsible for
the production of some hormones. One egg is produced every month by
one of the ovaries. The egg is carried from the ovary to a thin oviduct or
fallopian tube. The two oviducts unite into an elastic bag-like structure
known as the uterus. After the fertilisation of the egg it is sent to the
uterus(womb) The uterus opens into the vagina through the cervix.
Through the vagina baby is released but the path for urine is different.
Q. What happens during and after mating in humans?
Ans. During mating in humans the sperms in the form of semen enter
through the vaginal passage. They travel upwards and reach the oviduct
where they may
encounter an egg. Fusion and fertilisation takes place in the oviduct. The
fertilised egg (zygote) starts dividing and forms a ball of cells or embryo.
The embryo is implanted in the lining of the uterus where they continue to
grow and develop organs to become a foetus. The lining thickens and is
richly supplied with blood to nourish the growing embryo or foetus.
Q. How does an embryo get nutrition and get rid of waste products?
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Ans. The embryo gets nutrition from the mother’s blood with the help of a
special tissue called placenta. This is a disc which is embedded in the
uterine wall. It contains villi on the embryo’s side of the tissue. On the
mother’s side are blood spaces, which surround the villi. This provides a
large surface area for glucose and oxygen to pass from the mother to the
embryo. The developing embryo will also generate waste substances which
can be removed by transferring them into the mother’s blood through the
placenta. The development of the child inside the mother’s body takes
approximately nine months and this period is called gestation. The child is
born as a result of rhythmic contractions of the muscles in the uterus.
Q. What is menstruation or menstrual cycle and why and what happens
during menstruation?
Ans. One egg is produced every month by one of the ovaries. The egg is
sent to the oviduct for fertilisation, it lives for about one day. Since the ovary
releases one egg every month, the uterus also prepares itself every month
to receive a fertilised egg. Thus its lining becomes thick and spongy. This
would be required for nourishing the embryo if fertilisation had taken place.
If the egg is not fertilised, this lining is not needed any longer. So, the lining
slowly breaks and comes out through the vagina as blood and mucous.
This cycle takes place roughly every month and is known as menstruation.
It usually lasts for about two to eight days. The menstrual cycle is controlled
by hormones.
The first occurrence of menstruation (or periods) at puberty is called
menarche and the permanent stoppage of menstruation (or periods) in a
woman is called menopause.
Q. What is Reproductive Health and what are the methods to prevent
them?
Ans. Reproductive health refers to a state of complete physical, mental, and
social well-being related to the reproductive system, including the ability to
have a satisfying and safe sex life, the capability to reproduce, and the
freedom to decide if, when, and how often to do so. There are many diseases
which transmit during sex from an infected person to a healthy person, like
bacterial infections such as gonorrhoea and syphilis, and viral infections such
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as warts and HIV-AIDS. The diseases which are spread by sexual contact
with an infected person are called sexually transmitted diseases (or STD).
Use of condoms while having sex, prevents sexually transmitted
diseases.
Q. How to avoid unwanted pregnancies?
Ans. The prevention of pregnancy in women (by preventing fertilisation) is
called contraception. And any device or chemical (drug) which prevents
pregnancy in women is called a contraceptive. All the birth control methods
can be broadly divided into three categories :-
1. Barrier methods:- Use of Condom (also known as ‘Nirodh’)
2. Chemical methods:- Use of pills, which contains hormones which
stop the ovaries from releasing ovum (or eggs) into the oviduct.
3. Intra-Uterine Contraceptive Device:- Placing copper-T inside uterus.
4. Surgical methods:- The surgical procedure carried out in males is
called ‘vasectomy’ and the surgical procedure carried out in females
is called tubectomy.
Q. How is the process of pollination different from fertilisation?
Ans.
Pollination
Fertilisation
It is the transfer of pollen grain from
anther to stigma.
It is the fusion of male gamete and
female gamete.
Some agents are required.
No agents are required.
It is an external process.
It may be an internal or external
process.
It is a physical process.
It is a biochemical process.
After the pollination, fertilisation
occurs.
After the fertilisation, a zygote is
formed.
Q. What is the role of the seminal vesicles and the prostate gland?
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Ans. The seminal vesicles and the prostate gland are found in male
reproductive system which add their secretion so that the sperms are now
in a fluid which makes their transport easier and this fluid also provides
nutrition. They together are now called semen.
Q. What are the changes seen in girls at the time of puberty?
Ans. At the time of puberty following changes are seen in girls:-
1. Thick hair in the armpits and the genital area starts growing
2. Thinner hair can also appear on legs and arms, as well as on the
face.
3. The skin frequently becomes oily and develops pimples.
4. Ovaries begin to grow and start maturing their sex cells(eggs).
5. Breast size begins to increase.
6. Darkening of the skin of the nipples at the tips of the breasts.
7. They begin to menstruate(Periods) at around this time.
Q. How does the embryo get nourishment inside the mother’s body?
Ans. The embryo gets nourishment from the mother’s blood with the help
of a special tissue called placenta. This is a disc which is embedded in the
uterine wall. It contains villi on the embryo’s side of the tissue. On the
mother’s side are blood spaces, which surround the villi. This provides
a large surface area for glucose and oxygen to pass from the mother to
the embryo.
Q. If a woman is using a copper -T, will it help in protecting her from
sexually transmitted diseases?
Ans. Using copper - T will not help in protecting from sexually transmitted
diseases. Because it does not prevent the mixing of body fluids. It only
prevents pregnancy.
Exercises
1. Asexual reproduction takes place through budding in
(a) Amoeba.
(b) Yeast.
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(c) Plasmodium.
(d) Leishmania.
Ans. Amoeba
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
Ans. Vas deferens
3. The anther contains
(a) Sepals.
(b) Ovules.
(c) Pistil.
(d) Pollen grains.
Ans. Pollen grains.
4. What are the advantages of sexual reproduction over asexual
reproduction?
Ans. Following are the advantages of sexual reproduction over asexual
reproduction:-
1. More variation is found.
2. Organisms produced by sexual reproduction have a greater survival
rate.
3. The new formed individual has characteristics of both the parents.
5. What are the functions performed by the testis in human beings?
Ans. The following functions performed by the testis in human beings:-
1. Production of male sex cells.
2. Production of male hormones.
3. Regulating reproductive function.
6. Why does menstruation occur?
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Ans. During puberty in girls, one egg is produced every month by one of
the ovaries. The egg is sent to the oviduct for fertilisation, it lives for about
one day. Since the ovary releases one egg every month, the uterus also
prepares itself every month to receive a fertilised egg. Thus its lining
becomes thick and spongy. This would be required for nourishing the
embryo if fertilisation had taken place. If the egg is not fertilised, this lining
is not needed any longer. So, the lining slowly breaks and comes out
through the vagina as blood and mucous. This cycle takes place roughly
every month and is known as menstruation. It usually lasts for about two to
eight days.
7. Draw a labelled diagram of the longitudinal section of a flower.
Ans.
8. What are the different methods of contraception?
Ans. The prevention of pregnancy in women (by preventing fertilisation) is
called contraception. And any device or chemical (drug) which prevents
pregnancy in women is called a contraceptive. All the birth control methods
can be broadly divided into three categories :-
5. Barrier methods:- Use of Condom (also known as ‘Nirodh’)
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6. Chemical methods:- Use of pills, which contains hormones which
stop the ovaries from releasing ovum (or eggs) into the oviduct.
7. Intra-Uterine Contraceptive Device:- Placing copper-T inside uterus.
8. Surgical methods:- The surgical procedure carried out in males is
called ‘vasectomy’ and the surgical procedure carried out in females
is called tubectomy.
9. How are the modes for reproduction different in unicellular and
multicellular organisms?
Ans.
Reproduction in unicellular
Reproduction in multicellular
Asexual mode of reproduction is
used.
Asexual or sexual mode of
reproduction is used.
Identical organisms are produced.
Non identical organisms are
produced.
No special tissue is required.
Special tissue is required.
Example:- Yeast, Amoeba.
Example:- plants, animals, hydra.
10. How does reproduction help in providing stability to populations of
species?
Ans. Any organism in the earth has a life span after which it dies but during
reproduction the organisms produce a similar organism which increases
the population of the species, in addition to this during reproduction some
variation occur which help the organism to survive in a drastic change in
their environment and provides stability to the population of species.
11. What could be the reasons for adopting contraceptive methods?
Ans. There could be the following reasons for adopting contraceptive
methods :-
1. To prevent unwanted pregnancies.
2. To maintain a periodic gap between their two successive childs.
3. To prevent the transfer of sexually transmitted diseases.
