Question 5:
How does the progeny formed from asexual reproduction differ from those
formed by sexual reproduction?
Answer 5:
Progeny formed from asexual Progeny formed from sexual
reproduction reproduction
1. Asexual reproduction does not involve Sexual reproduction involves the
the fusion of the male and the female fusion of the male and the female
gamete. Organisms undergoing this gamete of two individuals, typically
kind of reproduction produce one of each sex. Organisms
offspring’s that are morphologically undergoing this kind of reproduction
and genetically identical to them produce offspring’s that are not
identical to them.
2.Offsprings thus produced do not show Offspring’s thus produced show
variations and are called clones. variations from each other and their
parents.
Question 6:
What is vegetative propagation? Give two suitable examples.
Answer 6:
Vegetative propagation is a mode of asexual reproduction in which new
plants are obtained from the vegetative parts of plants. It does not involve
the production of seeds or spores for the propagation of new plants.
Vegetative parts of plants such as runners, rhizomes, suckers, tubers, etc.
can be used as propagules for raising new plants.
Examples of vegetative reproduction are:
1. Eyes of potato:
The surface of a potato has several buds called eyes. Each of these buds
when buried in soil develops into a new plant, which is identical to the
parent plant.
2. Leaf buds of Bryophyllum:
The leaves of Bryophyllum plants bear several adventitious buds on their
margins. These leaf buds have the ability to grow and develop into tiny
plants when the leaves get detached from the plant and come in contact with
moist soil.
Question 8:
Define
(a) Juvenile phase,
(b) Reproductive phase,
(c) Senescent phase.
Answer 8:
(a) Juvenile phase:
It is the period of growth in an individual organism after its birth and before
it reaches reproductive maturity.
(b) Reproductive phase:
It is the period when an individual organism reproduces sexually.
(c) Senescent phase:
It is the period when an organism grows old and loses the ability to
reproduce.
Question 9:
Higher organisms have resorted to sexual reproduction in spite of its
complexity. Why?
Answer 9:
Although sexual reproduction involves more time and energy, higher
organisms have resorted to sexual reproduction in spite of its complexity.
This is because this mode of reproduction helps introduce new variations in
progenies through the combination of the DNA from two (usually) different
individuals. These variations allow the individual to cope with various
environmental conditions and thus, make the organism better suited for the
environment. Variations also lead to the evolution of better organisms and
therefore, provide better chances of survival. On the other hand, asexual
reproduction does not provide genetic differences in the individuals
produced.
Question 10:
Explain why meiosis and gametogenesis are always interlinked?
Answer 10:
Meiosis is a process of reductional division in which the amount of genetic
material is reduced. Gametogenesis is the process of the formation of
gametes. Gametes produced by organisms are haploids (containing only one
set of chromosomes), while the body of an organism is diploid. Therefore,
for producing haploid gametes (gametogenesis), the germ cells of an
organism undergo meiosis. During the process, the meiocytes of an
organism undergo two successive nuclear and cell divisions with a single
cycle of DNA replication to form the haploid gametes.
Question 11:
Identify each part in a flowering plant and write whether it is haploid (n) or
diploid (2n).
(a) Ovary ———————————
(b) Anther ———————————
(c) Egg ———————————
(d) Pollen ———————————
(e) Male gamete ———————————
(f ) Zygote ———————————
Answer 11:
(a) Ovary Diploid (2n)
(b) Anther Diploid (2n)
(c) Egg Haploid (n)
(d) Pollen Haploid (n)
(e) Male gamete Haploid (n)
(f ) Zygote Diploid (2n)
Question 12:
Define external fertilization. Mention its disadvantages.
Answer 12:
External fertilization is the process in which the fusion of the male and the
female gamete takes place outside the female body in an external medium,
generally water.
Fish, frog, starfish are some organisms that exhibit external fertilization.
Disadvantages of external fertilization:
In external fertilization, eggs have less chances of fertilization. This can lead
to the wastage of a large number of eggs produced during the process.
Further, there is an absence of proper parental care to the offspring,
How does the progeny formed from asexual reproduction differ from those
formed by sexual reproduction?
Answer 5:
Progeny formed from asexual Progeny formed from sexual
reproduction reproduction
1. Asexual reproduction does not involve Sexual reproduction involves the
the fusion of the male and the female fusion of the male and the female
gamete. Organisms undergoing this gamete of two individuals, typically
kind of reproduction produce one of each sex. Organisms
offspring’s that are morphologically undergoing this kind of reproduction
and genetically identical to them produce offspring’s that are not
identical to them.
2.Offsprings thus produced do not show Offspring’s thus produced show
variations and are called clones. variations from each other and their
parents.
Question 6:
What is vegetative propagation? Give two suitable examples.
Answer 6:
Vegetative propagation is a mode of asexual reproduction in which new
plants are obtained from the vegetative parts of plants. It does not involve
the production of seeds or spores for the propagation of new plants.
Vegetative parts of plants such as runners, rhizomes, suckers, tubers, etc.
can be used as propagules for raising new plants.
Examples of vegetative reproduction are:
1. Eyes of potato:
The surface of a potato has several buds called eyes. Each of these buds
when buried in soil develops into a new plant, which is identical to the
parent plant.
2. Leaf buds of Bryophyllum:
The leaves of Bryophyllum plants bear several adventitious buds on their
margins. These leaf buds have the ability to grow and develop into tiny
plants when the leaves get detached from the plant and come in contact with
moist soil.
Question 8:
Define
(a) Juvenile phase,
(b) Reproductive phase,
(c) Senescent phase.
Answer 8:
(a) Juvenile phase:
It is the period of growth in an individual organism after its birth and before
it reaches reproductive maturity.
(b) Reproductive phase:
It is the period when an individual organism reproduces sexually.
(c) Senescent phase:
It is the period when an organism grows old and loses the ability to
reproduce.
Question 9:
Higher organisms have resorted to sexual reproduction in spite of its
complexity. Why?
Answer 9:
Although sexual reproduction involves more time and energy, higher
organisms have resorted to sexual reproduction in spite of its complexity.
This is because this mode of reproduction helps introduce new variations in
progenies through the combination of the DNA from two (usually) different
individuals. These variations allow the individual to cope with various
environmental conditions and thus, make the organism better suited for the
environment. Variations also lead to the evolution of better organisms and
therefore, provide better chances of survival. On the other hand, asexual
reproduction does not provide genetic differences in the individuals
produced.
Question 10:
Explain why meiosis and gametogenesis are always interlinked?
Answer 10:
Meiosis is a process of reductional division in which the amount of genetic
material is reduced. Gametogenesis is the process of the formation of
gametes. Gametes produced by organisms are haploids (containing only one
set of chromosomes), while the body of an organism is diploid. Therefore,
for producing haploid gametes (gametogenesis), the germ cells of an
organism undergo meiosis. During the process, the meiocytes of an
organism undergo two successive nuclear and cell divisions with a single
cycle of DNA replication to form the haploid gametes.
Question 11:
Identify each part in a flowering plant and write whether it is haploid (n) or
diploid (2n).
(a) Ovary ———————————
(b) Anther ———————————
(c) Egg ———————————
(d) Pollen ———————————
(e) Male gamete ———————————
(f ) Zygote ———————————
Answer 11:
(a) Ovary Diploid (2n)
(b) Anther Diploid (2n)
(c) Egg Haploid (n)
(d) Pollen Haploid (n)
(e) Male gamete Haploid (n)
(f ) Zygote Diploid (2n)
Question 12:
Define external fertilization. Mention its disadvantages.
Answer 12:
External fertilization is the process in which the fusion of the male and the
female gamete takes place outside the female body in an external medium,
generally water.
Fish, frog, starfish are some organisms that exhibit external fertilization.
Disadvantages of external fertilization:
In external fertilization, eggs have less chances of fertilization. This can lead
to the wastage of a large number of eggs produced during the process.
Further, there is an absence of proper parental care to the offspring,
