The Life Cycle
Q1. Fill in the blanks.
1.
The two main methods of reproduction are
_____________ and ________________. (sexual reproduction, asexual reproduction)
2.
The functional unit in a plant’s sexual
reproduction is ____________. (flower)
3.
The male reproductive part of a flower is
_____________(stamen)
4.
When the transfer of pollen from an anther to the
stigma occurs in the same flower, the process is called ____________. (self
pollination (autogamy))
5.
________ give rise to variety and diversity. (variation)
6.
Hydra uses regenerative cells for reproduction in
the process of _________. (budding)
7.
Yeast reproduces by _____________. (budding)
8.
During unfavourable conditions ___________ type of
fission is seen in amoeba. (multiple)
9.
A basic process in reproduction is the creation of
a _____________ copy. (DNA)
10. _______________
is necessary to maintain the number of individuals of a species. (Reproduction)
Q2. Write the correlated terms:
1.
Amoeba: Simple binary fisson : : Paramoecium:
______________(Transverse binary fission)
2.
Planaria :
regeneration : : Rhizopus :
________________(spore formation)
3.
Root, stem, leaf : Vegetative propogation : : Flower : ______________(sexual
reproduction)
4.
Asexual reproduction : similarity : : Sexual reproduction
: ____________ (diversity)
Q4. Explain the following terms.
1.
Reproduction: - The fundamental characteristic of
living things to produce new individuals of the same species, that is a new
generation of the species from and existing individual is known as
reproduction.
2.
Vegetative propogation: -When new
plants are produced from the vegetative parts like roots, stems, leaves and
buds it is known as vegetative propagation.
3.
Pollination:- The process of transfer of pollen grains from
anther to stigma is called as pollination.
Q5. Write the functions of the
following organs in reproduction.
1.
Vagina
i.
It provides the route for the menstrual blood to
leave the body during menstruation.
ii.
It is a pathway through which sperms enters into
woman’s body.
iii.
It is a pathway through which a baby comes out of
the woman’s body during child birth.
2.
Stigma
i.
It receives pollen grains and on which pollen
germinates.
3.
Ovaries
i.
Ovaries develop and release eggs into the oviduct.
ii.
It secretes hormone estrogen.
4.
Seminal vesicle and Prostate glands
i.
Produce ejaculatory fluid which helps the sperm in
transport and provides nutrition.
5.
Uterus
i.
It accommodates a growing foetus.
ii.
It push the baby during labour.
Q6. Draw a well labeled diagram of:
[refer to text book]
1.
Longitudinal section of flower.
2.
Binary fission in amoeba.
3.
Spore formation in Mucor.
4.
Human female reproductive system.
Q7. Answer the following.
1.
What are the advantages of sexual reproduction over
asexual reproduction?
Ans.
i.
The offsprings produced by sexual reproduction are
different from parents.
ii.
Variations give rise to variety and diversity.
iii.
Variation enables organisms to adapt and survive in
the changing environment.
iv.
It helps to prevent the complete extinction of
animal and plant species.
2.
Why does menstruation occur?
Ans.
i.
A woman’s ovaries usually release one egg each
month.
ii.
When the egg is not fertilized, menstruation occurs
to leave out the unfertilized egg along with blood and mucous from the uterus.
3.
Describe sexual reproduction in plants.
Ans.
i.
In plants, flower is the functional unit concerned
with sexual reproduction.
ii.
In a flower, the ovary produced female germ cell or
egg and the pollen grains produces male germ cells.
iii.
When the pollen lands on stigma, it germinates
producing a pollen tube which grow downwards to reach ovary.
iv.
Each pollen tube contains two male gametes and are
released near the egg,
v.
One male gamete fuse with the egg cell to form
zygote.
vi.
The second male gamete fuse with the secondary
nucleus in the embryo sac to form endosperm. This is called as double
fertilization.
vii.
The zygote develops into embryo and the endosperm
serves as nutritive tissue for the growing embryo.
4.
Describe the modes of reproduction in unicellular
organisms.
Ans. Binary fission, multiple fission and budding are the modes of
sexual reproduction in unicellular organisms.
a. Binary fission:
-
i.
It is employed by most prokaryotes, some protozoa
and some organelles within eukaryotic cells.
ii.
In it, the living cell divides into two equal parts
which have the potential to grow to the size of the original one.
b. Multiple
fission: -
i.
During unfavourable condition, the amoeba withdraws
its pseudopodia and form a cyst.
ii.
Inside the cyst, nucleus divides into many nuclei
and as a result many daughter cells are formed.
iii.
The cyst bursts to release the daughter cells
during favourable condition.
c. Budding: -
i.
Yeast reproduces by budding in which a small
outgrowth is formed on the parental cell.
ii.
The nucleus of the parental call divides and one
daughter nucleus migrates into the bud. The bud increases in size separates and
grows further.
5.
Explain disadvantages of large family size.
Ans.
i.
There is a strong relation between high national
fertility rate and measures of poverty.
ii.
As the population density increases, decrease in
per capital income and natural resources takes place.
iii.
General health goes down and creates an economical
burden on the nation.
iv.
Large families affect both the individual as well
as the community life.
v.
Economic pressure, mother’s poor health, children
neglected at home, poor nourishing, malnutrition, insufficient medical care,
lack of better education, etc., are some of the disadvantages of large family
size.
Q8. Write short notes on the
following:
1.
Pollination: -
i.
The process of transfer of pollen grains from
anther to stigma is called as pollination.
ii.
If this transfer of pollen occurs in the same
flower or another flower of the same plant, it is known as self pollination.
iii.
On the other hand, if pollen is transferred from
one flower to the flower of another plant, it is known as cross pollination.
iv.
The agents of cross pollination are wind, water or
animals.
2.
Regeneration: -
i.
The capacity to regenerate is very high among some
animals.
ii.
They can reconstruct the entire body from the
isolated body cells.
iii.
Regeneration is carried out by specialized cells.
iv.
These cells proliferate and make large number of
cells which later developed into various cell types and tissues, and helps in
production of new organism.
v.
Eg. When Planaria is cut into many pieces, each
piece develops into a whole Planaria. This process occurs only if the Planaria
body gets cut up into pieces. But animals cannot wait to be cut to reproduce.
So regeneration is not the same as reproduction.
3.
Germination of seeds : -
i.
After fertilization, the zygote divides several
times to form an ambryo within the ovule.
ii.
The ovule develops into a seed and ovary develops
into the fruit.
iii.
The seed contains the future plant. It develops
into the seedling under appropriate condition. This process is known as
germination.
4.
Multiple fission: -
i.
During unfavourable condition, the amoeba withdraws
its pseudopodia, becomes almost round and secretes a hard covering called cyst.
ii.
Inside the cyst nucleus divides into many nuclei by
repeated division, follow by division of cytoplasm.
iii.
As a result many daughter cells are formed.
iv.
The cyst bursts to release the daughter cells
during favourable condition.
5.
Importance of variation.
i.
Changes in ecological system, which are beyond our
control like varying temperature, varying water level can wipe out the
population species.
ii.
But, if variations in some individuals are suitable
for new environment, there is a chance of survival of that species.
