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12.
282
The Life Cycle
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SCIENCE & TECHNOLOGY
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(A) Choose the correct alternatives and rewrite the complete sentences :
The filament of spirogyra undergoes ....................... resulting in numerous
filaments.
(a) budding
(b) regeneration
(c) fragmentation
(d) spore formation
....................... reproduces from the buds on the leaf margin.
(a) Lotus
(b) Rose
(c) Jasmine
(d) Bryophyllum
....................... is the receptive organ on which pollen germinates.
(a) Style
(b) Stigma
(c) Anther
(d) Ovary
The elongated part of carpel bearing stigma at its tip is called ..................... .
(a) style
(b) stigma
(c) anther
(d) ovary
In plants, male germ cells are produced by ....................... .
(a) filament
(b) anther
(c) pollen grains
(d) stamen
....................... serves as nutritive tissue for the growing embryo.
(a) Embryo sac
(b) Endosperm
(c) Ovary
(d) Fruit
The ovule develops into a ....................... .
(a) fruit
(b) seed
(c) flower
(d) ovary
The ovary develops into a ....................... .
(a) fruit
(b) seed
(c) flower
(d) ovule
Testes secrete the hormone ....................... which brings about changes
in boys during puberty.
(a) progesterone
(b) estrogen
(c) thyroxine
(d) testosterone
Immature sperms travel to the ....................... for development and storage.
(a) vas deferens
(b) penis
(c) testes
(d) epididymis
....................... is a passage through which the sperm travels towards the
urethra.
(a) Vas deferens
(b) Penis
(c) Epididymis
(d) Seminal vesicle
The ovaries secrete the hormone ....................... which brings about changes
in girls during puberty.
(a) progesterone
(b) estrogen
(c) thyroxine
(d) testosterone
Planaria reproduces by ....................... .
(a) fragmentation
(b) budding
(c) binary fission
(d) regeneration
Answers :
1. fragmentation
3. Stigma
5. pollen grains
7. seed
9. testosterone
11. Vas deferens
13. regeneration
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4.
6.
8.
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Bryophyllum
style
Endosperm
fruit
epididymis
estrogen
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*5.
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*10.
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(B) Fill in the blanks :
The two main methods of reproduction are ....................... and
....................... .
The functional unit in a plant’s sexual reproduction is ....................... .
The male reproductive part of a flower is ....................... .
When the transfer of pollen from an anther to the stigma occurs in the
same flower, the process is called ....................... .
....................... give rise to variety and diversity.
Hydra uses regenerative cells for reproduction in the process of
....................... .
Yeast reproduces by ....................... .
During unfavourable conditions, the amoeba secretes a hard covering called
....................... .
A basic process in reproduction is the creation of a ....................... copy.
....................... is necessary to maintain the number of individuals of a
species.
In asexual reproduction the cells divide ....................... .
The ....................... of bread mould (Mucor) are thread like structures.
The mould forms spores inside a ....................... .
....................... is the process by which an entire organism is reproduced
in a genetically identical manner, from a parent organism.
....................... enables organisms to adapt and survive in the changing
environment.
Stamen is made up of ....................... and ....................... .
If pollen is transferred from one flower to the flower of another plant of the
same species, it is known as ....................... .
One male gamete fuses with the egg cell to form ....................... .
The second male gamete fuses with the secondary nucleus in the embryo
sac to form ....................... .
....................... is a muscular tube that extends from the vaginal opening
to the uterus.
....................... provides the route for the menstrual blood to leave the
body during menstruation.
....................... connect uterus to the ovary.
The embryo gets all the nutrients and oxygen from its mother’s blood in
the oviduct supplied through the ....................... .
The ....................... has prepared guidelines and considered reproductive
health as a fundamental human right.
....................... was the first mammal to be cloned from an adult cell rather
than an embryo.
As soon as the egg cell (zygote) is fertilized, it begins to divide until it
becomes a ball of cells called ....................... .
Answers :
1. asexual reproduction,
sexual reproduction
3. stamen
5. Variations
7. budding
9. DNA
11. mitotically
13. sporangium
15. variation
17. cross pollination
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2.
4.
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8.
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12.
14.
16.
18.
flower
self pollination
budding
multiple
Reproduction
hyphae
Animal cloning
anther, filament
zygote
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19.
21.
23.
25.
endosperm
Vagina
umbilical cord
Dolly sheep
Q.I
1.
(i)
(ii)
(iii)
(iv)
(v)
(C) Match the following :
Column I
Penis
Ovaries
Oviduct
Testes
Epididymis
20.
22.
24.
26.
Vagina
Oviducts
WHO
Blastocyst.
Ans.
Column II
(a) Site of fertilization
(b) Stores sperms
(c) Delivers sperms
(d) Produce eggs
(e) Produce sperms
(f) Provides nutrition
(i - c), (ii - d), (iii - a), (iv - e), (v - b).
2.
(i)
(ii)
(iii)
(iv)
(v)
Ans.
Column I
Amoeba
Yeast
Bryophyllum
Mucor
Spirogyra
(i - c), (ii - d), (iii - b), (iv - e),
Q.I
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Column II
(a) Fragmentation
(b) Vegetative propagation
(c) Binary fission
(d) Budding
(e) Spore formation
(v - a).
(D) State whether the following statements are true or false. If false
write the corrected statement :
Lack of genetic variation is the advantage of asexual reproduction.
False. Lack of genetic variation is the disadvantage of asexual reproduction.
DNA copies are identical to the original.
False. DNA copies are similar but not identical to the original.
Mitosis is a process in which halving the number of chromosomes takes
place.
False. Mitosis is a process in which the chromosome number is restored.
Meiosis is a process in which halving the number of chromosomes takes
place.
True.
Testes secrete the hormone testosterone.
True.
Immature sperms travel to the vas deferens for storage.
False. Immature sperms travel to the Epididymis for storage.
Spirogyra reproduces by regeneration.
False. Spirogyra reproduces by fragmentation.
On reaching puberty, a woman’s ovaries usually release thousands of eggs
each month.
False. On reaching puberty, a woman’s ovaries usually release one egg
each month.
If pollination occurs from one flower to another flower of the same plant, it
is called cross-pollination.
False. If pollination occurs from one flower to another flower of the same
plant, it is called self-pollination.
Carpel is the female reproductive part of a flower.
True.
Cloned animal has the DNA which is identical to parent DNA.
True.
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Boys become adults at the age of 18.
False. Boys become adults at the age of 21.
Q.I
1.
Ans.
(E) Find the odd man out :
Stigma, Style, Anther, Ovary.
Anther. It is the male reproductive part of a flower whereas the others are
female reproductive parts of the flower.
Vagina, Uterus, Testis, Ovaries.
Testis. It is a male reproductive organ whereas the others are female
reproductive organs.
Bryophyllum, Potato, Sweet potato, Spirogyra.
Spirogyra. It reproduces by fragmentation whereas the others reproduce
by vegetative propagation.
Syphilis, Gonorrhoea, Malaria, AIDS.
Malaria. It is not a sexually transmitted disease whereas the others are
sexually transmitted diseases.
Root, Stem, Leaf, Flower.
Flower. It is the reproductive part of a plant whereas the others are
vegetative parts of a plant.
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Q.I
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(F) Write the correlated terms :
Amoeba : Simple binary fission :: Paramoecium : ....................... .
Transverse binary fission.
Planaria : Regeneration :: Rhizopus : ....................... .
Spore formation.
Root, Stem, Leaf : Vegetative propagation :: Flower : ....................... .
Sexual reproduction.
Asexual reproduction : Similarity :: Sexual reproduction : ....................... .
Diversity.
Testis : Testosterone :: Ovaries : ....................... .
Estrogen.
Ovule : Seed :: Ovary : ....................... .
Fruit.
Asexual reproduction : Somatic cells :: Sexual reproduction : ....................... .
Germ cells.
Spirogyra : Fragmentation :: Planaria : ....................... .
Regeneration.
Q.II
*1.
Ans.
Define the following :
Reproduction.
The process of production of new individuals of the same species, that is a new
generation of the species from an existing individual is called as reproduction.
Vegetative propagation.
When new plants are produced from the vegetative parts (roots, stems,
leaves and buds), it is known as vegetative propagation.
Pollination.
The process of transfer of pollen grains from anther to stigma is called as
pollination.
Meiosis.
It is a process in which halving the number of chromosomes (2n to n) takes
place resulting in the formation of haploid gametes.
Mitosis.
It is a type cell division occuring in somatic cells leading to growth and
development.
*2.
Ans.
*3.
Ans.
*4.
Ans.
5.
Ans.
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Fertilization.
It is a process in which male gamete fuses with the female gamete resulting
in the formation of diploid zygote.
Q.III (A) Give scientific reasons :
1. DNA copies generated during reproduction are similar but not identical
to the original.
Ans. 1. A basic process in reproduction is the creation of a DNA copy.
2. Cells use chemical reactions to create copies of their DNA.
3. In this process of copying, some variations take place each time.
4. Therefore, DNA copies generated during reproduction are similar but
not identical to the original.
2. Daughter cells produced by asexual reproduction are genetically identical
to the parent cells.
Ans. 1. Only one parent is involved in asexual reproduction in which the cells
divide mitotically.
2. Since, there is no fusion of two different cells, the daughter cells
produced by asexual reproduction are genetically identical to the parent
cells.
3. Multicellular organisms show complex ways of reproduction.
Ans. 1. Multicellular organisms have different cell types which perform different
functions.
2. They have special organs, placed at a definite place in the body which
are formed by specific tissues.
3. In such organised organisms, method of cell-by-cell division to reproduce
is impractical.
4. Therefore, multicellular organisms show complex ways of reproduction.
*4. Siberian cranes migrate to Bharatpur during winter.
Ans. 1. Winter is very severe at Siberia in Russia.
2. Siberian cranes cannot tolerate such extremely low temperatures.
3. In Bharatpur, India, the climate is comparatively warmer and food is
available in plenty.
4. Therefore, to escape from the unfavourable climatic conditions, Siberian
cranes migrate to Bharatpur during winter.
*5. In the absence of honey bees, the yield of sunflower goes down
tremendously.
Ans. 1. Sunflower pollen is heavy and sticky. So it cannot be carried by wind.
2. So, pollen is transferred from one plant to another plant through the
agency of honey bees resulting in cross pollination.
3. Cross pollination also increases the yield of seeds.
4. Therefore, in the absence of honey bees, the yield of sunflower goes
down tremendously.
6. Testes are located outside the abdominal cavity in the scrotum.
Ans. 1. Testes are the organs which produce sperms (male germ cells).
2. Formation of sperms requires temperature lower than the normal body
temperature.
3. Therefore, testes are located outside the abdominal cavity in the scrotum.
7. Children born to older women may be defective.
Ans. 1. At birth, the female ovary contains approximately 2-4 million eggs. After
birth, new eggs are not added.
2. Out of this eggs, only about 400 are destined to be ovulated, while all others
degenerate during development, so that only a few remain by the age of 50.
3. Thus, eggs ovulated near the age of 50 are 30-40 years older than
those ovulated just after puberty.
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4. This ageing of eggs can cause defects in the children born to older
women.
Regeneration is not the same as reproduction.
1. Regeneration is the reconstruction of entire body from the isolated
body cells.
2. Eg. When planaria is cut into many pieces, each piece develops into a
whole planaria.
3. This process occurs only if the planarial body gets cut into pieces.
4. But animals cannot wait to be cut to reproduce.
5. Therefore, regeneration is not the same as reproduction.
Q.III (B) Answer the following questions in short :
*1. What are the advantages of sex ual reproduction over asex ual
reproduction ?
Ans. 1. Sexual reproduction promotes diversity of characters in the offsprings.
2. In sexual reproduction, due to genetic variation there is more opportunity
for new combination of characters and therefore, it plays a prominent
role in the origin of new species.
3. It also leads to variation, which is necessary for evolution. Variation
enables the organisms to adapt and survive in the changing environment.
4. It helps to prevent the complete extinction of animal and plant species.
*2. Why does menstruation occur ?
Ans. 1. On reaching puberty, a woman’s ovaries usually release one egg each
month.
2. When the egg is not fertilized, this unfertilized egg along with blood
and mucous form a flow which leaves the uterus. This is called
menstruation which lasts for three to five days.
*3. Explain disadvantages of large family size.
Ans. 1. There is a strong relation between high national fertility rate and
measures of poverty.
2. As the population density increases, decrease in per capita income
and natural resources takes place.
3. General health also goes down.
4. It creates an economic burden on the nation.
5. Large families affect both the individual as well as the community life.
6. Economic pressure, mother’s poor health, children neglected at home,
poor housing, malnutrition, insufficient medical care, lack of better
education are some of the disadvantages of large family size.
4. Describe the formation of twins.
Ans. 1. Sometimes a single fertilized egg may get split and separated into two
parts during the early stage of cell division. Each part then develops
into a separate individual. As these individuals are produced from a
single zygote, they look similar and are called identical twins (either
both boys or both girls).
2. Sometimes two eggs are released from ovaries simultaneously and get
fertilized to produce two individuals. As these two individuals are
produced from different zygote, they are dissimilar (either both boys or
both girls or one boy and one girl).
5. What is mitosis ? Represent in diagramatically.
Ans. 1. Mitosis is a type of cell division leading to growth and development.
2. It occurs in somatic cells.
3. Diagramatically it can be represented as :
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Parent cell
2n
2n
2n
6.
Ans.
Two daughter cells
(restoring original
chromosomal number)
What is meiosis ? Represent it diagramatically.
1. Meiosis is a type of cell division leading to production of gametes.
2. It is a process in which halving the number of chromosomes (2n to n)
takes place resulting in the formation of haploid gametes.
3. It occurs in reproductive cells.
4. Diagramatically it can be represented as :
n
Mitosis
Parent cell Reduction division
2n
(diploid)
Meiosis
n
n
n
7.
Ans.
*8.
Ans.
9.
Ans.
10.
Ans.
11.
Ans.
12.
Ans.
n
Mitosis
Haploid
gametes
n
State the various modes of asexual reproduction in multicellular
organisms.
The various modes of reproduction in multicellular organisms are :
1. Fragmentation
2. Budding
3. Vegetative propagation
4. Spore formation.
What is reproduction ? What is its significance ?
1. All living organisms produce new individuals of the same species, that
is a new generation of the species from an existing individual. This
fundamental characteristic of living things is known as reproduction.
2. Reproduction is necessary to maintain the number of individuals of a
species and to prevent their extinction.
Describe asex ual reproduction. Also state its advantage and
disadvantage.
1. Only one parent is involved in asexual reproduction in which cells
divide mitotically.
2. Since there is no fusion of two different cells, the daughter cells
produced by asexual reproduction are genetically identical to the parent
cells.
3. Lack of genetic variation is the disadvantage while rapid reproduction
is the advantage of asexual reproduction.
What is the use of sepals and petals to the flower ?
1. Sepals protect the flower when it is in the bud condition.
2. Petals attract the insects for pollination.
3. Petals also protect the inner reproductive parts of the flower i.e., stamen
and carpel.
Why do some animals reproduce many young ones and some only one ?
1. All animals want to make sure that at least some of their young ones
reach adulthood and reproduce themselves.
2. Some animals do this by looking after a few young ones until they can
fend for themselves.
3. Other animals produce hundreds of eggs which they leave to develop
by themselves. Most of them will die, but a few will survive.
What are sperms ? Give the structure of a sperm cell.
1. Sperms are male germ cells.
2. A sperm cell is composed of a head which carries the genetic
information.
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3. It has a middle part which carries mitochondria
required for energy production.
4. It has a tail which is like a flagellum to help in
movement towards the female germ cells.
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Head
Midpiece
Tail
Sperm cell
13.
Ans.
What are STDs ? How can they be prevented ?
1. STDs are sexually transmitted diseases.
2. STDs spread from an infected person to a healthy person by unprotected
sexual contact.
3. Syphilis, Gonorrhoea, AIDS are some common sexually transmitted
diseases which affect the health of human being.
4. To protect individuals from these STDs, sex education and preventive
measures are necessary.
5. Use of condom protects the individual from STDs.
Q.III (C) Write short notes for the following :
*1. Pollination.
Ans. 1. The process of transfer of pollen grains from the anther to the stigma
is called pollination.
2. If this transfer of pollen occurs in the same flower or another flower of
the same plant, it is known as self pollination.
3. On the other hand, if pollen is transferred from one flower to the flower
of another plant of the same species, it is known as cross pollination.
The agents of cross pollination are wind, water or animals.
*2. Regeneration.
Ans. 1. The capacity to regenerate is very
high among some animals. They can
reconstruct the entire body from the
isolated body cells.
2. Regeneration is carried out by
specialised cells. These cells
proliferate and make large number
of cells which later develop into
various cell types and help in
production of new organisms.
3. For example, when planaria is cut
into many pieces, each piece
develops into a whole planaria.
Regeneration in planaria
4. This process occurs only if the
planarial body gets cut into pieces. But animals cannot wait to be cut
to reproduce. So regeneration is not the same as reproduction.
3. Budding in multicellular organisms (Hydra).
Ans. 1. Organisms such as hydra use
regenerative
cells
for
reproduction in the process of
budding.
Bud
2. When hydra reaches maturity and
Young
is well fed, its body wall begins to
hydra
form a rounded growth from the
Parent hydra
stalk of the adult.
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3. This growth is called a bud which develops in time into a miniature hydra.
4. The body layers, body cavity and the digestive cavity of the young hydra
are continuous with that of the parent hydra. The young hydra gets
nourishment from the parent.
5. When the young hydra is sufficiently developed to take up an individual
existence, the base of the new hydra seals off and thus allows the new
individual to break off from the parent hydra.
Vegetative propagation.
1. When new plants are produced from the vegetative parts (roots, stems,
leaves and buds), it is known as vegetative propagation.
2. For example, new plants of potato develop from eyes (buds on potato),
Bryophyllum reproduces from the buds on the leaf margin, the roots of
sweet potato give rise to new plants etc.
3. All plants produced by vegetative propagation are similar to the parent,
as they are produced from a single parent.
4. Plants produced by vegetative propagation take less time to grow and
bear flowers and fruits earlier than those produced from seeds.
Spore formation.
1. The hyphae of bread mould (Mucor) are Sporangium Spores
thread like structures.
2. The mould forms spores inside the
sporangium.
3. When the spores are ready to leave the
sporangium, it breaks open.
Hyphae
4. If they land in a moist place, they
germinate to form new mould.
Rhizoids
*6.
Ans.
Germination of seeds.
1. After fertilization, the zygote divides
several times to form an embryo
within the ovule.
2. The ovule develops into a seed and
ovary develops into the fruit.
3. The seed contains the future plant.
4. It develops into a seedling under
appropriate condition. This process is
known as germination.
*7.
Ans.
Multiple fission.
1. During unfavourable condition, the
amoeba
withdraws
its
pseudopodia, becomes almost
round and secretes a hard
covering called cyst.
2. Inside the cyst, the nucleus
Cyst
Multiple
Release of
divides into many nuclei by formation
fission
daughter cells
repeated division, followed by the
during
favourable
division of cytoplasm.
conditions
3. As a result, many daughter cells
are formed.
4. The cyst bursts to release the daughter cells during favourable condition.
Germination of a seed
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*8.
Ans.
Importance of variation.
1. Variation occurs due to sexual reproduction.
2. Variations give rise to variety and diversity.
3. It enables organisms to adapt and survive in the changing environment.
4. It helps to prevent the complete extinction of animal and plant species.
Q.IV
1.
Ans.
(A) Distinguish between :
Binary fission and Multiple fission.
2.
Ans.
Asexual reproduction and Sexual reproduction.
3.
Ans.
Pollination and Fertilization.
4.
Ans.
Self pollination and Cross pollination.
292
Binary fission
Multiple fission
1. In this method, the living cell 1. In this method, the nucleus
divides into two equal parts.
divides within the cyst into many
nuclei by repeated division.
2. In this method two daughter cells 2. In this method many daughter
are formed.
cells are formed.
3. It occurs under favourable 3. It occurs under unfavourable
conditions.
conditions.
Asexual reproduction
Sexual reproduction
1. Only one parent is involved in 1. Two parents are involved in
asexual reproduction.
sexual reproduction, one male
and the other female.
2. There is no fusion of two 2. There is fusion of two germ cells.
different cells.
3. It occurs in somatic cells.
3. It occurs in germ cells.
4. Offsprings are identical to the 4. Offsprings are different from
parent.
parents.
5. It is a rapid method of 5. It is a slow method of
reproduction.
reproduction.
Pollination
Fertilization
1. The process of transfer of pollen 1. The process in which the male
grains from the anther to the
gamete fuses with the female
stigma is called as pollination.
gamete
resulting
in
the
formation of a diploid zygote is
called fertilization.
2. It occurs only in plants.
2. It occurs in plants and animals.
3. It requires agents.
3. It does not require agents.
Self pollination
Cross pollination
1. If the transfer of pollen occurs 1. If the transfer of pollen occurs from
in the same flower or another
one flower to the flower of another
flower of the same plant, it is
plant of the same species, it is
known as self pollination.
known as cross pollination.
2. Offsprings
are
genetically 2. Offsprings are not genetically
identical.
identical.
3. Variations do not occur in the 3. Variations
occur
in
the
offsprings.
offsprings.
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5.
Ans.
Mitosis and Meiosis.
Q.IV
*1.
Ans.
(B) Draw a neat and labelled diagram of the following :
Longitudinal section of flower.
Mitosis
Meiosis
1. Mitosis is a type of cell division 1. Meiosis is a type of cell division
leading to growth and development.
leading to production of gametes.
2. It occurs in somatic cells.
2. It occurs in reproductive cells.
3. Chromosome number is restored. 3. Chromosome number is halved.
Stigma
Petal
Style
Carpel
Anther
Filament Stamen
Sepal
Ovary
*2.
Ans.
Binary fission in amoeba.
Parent cell
*3.
Ans.
Nucleus
dividing
Cytoplasm Two daughter
dividing
cells
Spore formation in Mucor.
Sporangium
Spores
Hyphae
Rhizoids
*4.
Ans.
Human female reproductive system.
Oviduct
Ovary Uterus
Endometrium
Cervix
Vagina
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Human male reproductive system.
Bladder
Seminal vesicle
Prostate gland
Vas deferens
Urethra
Epididymis
Testis
Penis
6.
Ans.
Budding in yeast.
Bud
Daughter
cells
Parent cell
Q.V
1.
Ans.
Answer the following in detail :
Describe the reproductive parts of a flower.
Stigma
Style
Petal
Carpel
Ovary
*2.
Ans.
294
Anther
Filament Stamen
Sepal
In plants, flower is the functional unit concerned with sexual reproduction.
The parts of the flower which are involved in reproduction are :
1. Carpel : Female reproductive part of a flower present in the centre. It
is made up of three parts : stigma, style and ovary.
2. Stigma : It is the sticky terminal part of the style. It is the receptive
organ on which pollen germinates.
3. Style : It is the elongated part of carpel bearing stigma at its tip.
4. Ovary : The swollen lower part of carpel containing one or more ovules.
Each ovule has an egg cell (female germ cell).
5. Stamen : Male reproductive part of a flower made up of two parts anther
and filament.
6. Anther : Usually bilobed and produces pollen grains.
7. Filament : Stalk of anther.
Describe sexual reproduction in plants.
The process of sexual reproduction in plants involves three processes :
1. Pollination
2. Fertilization
3. Germination.
SCHOOL SECTION
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Ans.
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1. Pollination :
a
(a) The process of transfer of pollen grains from
b
c
the anther to the stigma is called pollination.
(b) If this transfer of pollen occurs in the same
flower or another flower of the same plant,
it is known as self pollination.
(c) On the other hand, if pollen is transferred
from one flower to the flower of another plant
of the same species, it is known as cross
a, b : Self pollination
pollination. The agents of cross pollination c : Cross pollination
are wind, water or animals.
2. Fertilization :
(a) After the pollen grain lands on the stigma, it germinates.
(b) The pollen tube grows out from a pollen
Pollen grain
grain. It travels through the style to reach
Stigma
the ovary.
(c) Each pollen tube contains two male
Male germ
Cells (gamates)
gametes and releases them near the egg.
(d) One male gamete fuses with the egg cell
Pollen tube
to form zygote.
(e) The second male gamete fuses with the
Ovary
secondary nucleus in the embryo sac to
Secondary
nucleus
form endosperm. This is called as double
Female
fertilization.
germ cell
(f) The zygote develops into embryo and the
(egg cell)
endosperm serves as nutritive tissue for the
growing embryo. This embryo is capable of growing into a new plant.
3. Germination :
(a) After fertilization, the zygote divides several times to form an embryo
within the ovule.
(b) The ovule develops into a seed and ovary develops into the fruit.
(c) The seed contains the future plant. It develops into the seedling
under appropriate conditions. This process is known as germination.
Describe the modes of reproduction in unicellular organisms.
1. Binary fission :
(a) It is a method of asexual reproduction that is employed by most
prokaryotes, some protozoa and some organelles within eukaryotic cells.
(b) In this method, the
living cell divides
into two equal or
nearly equal parts
which have the
potential to grow to
the size of the
Nucleus Cytoplasm Two daughter
Parent cell
original one.
dividing dividing
cells
(c) The
plane
of
cytoplasmic division is through any plane in amoeba (simple binary
fission).
(d) However, in some organisms fission occurs through a specific axis
(transverse or longitudinal binary fission). Eg. : Paramoecium, Euglena.
2. Multiple fission :
(a) During unfavourable conditions the amoeba withdraws its
pseudopodia, becomes almost round and secretes a hard covering
called cyst.
SCHOOL SECTION
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SCIENCE & TECHNOLOGY
(b) Inside the cyst, nucleus divides
into many nuclei by repeated
division, followed by division of
cytoplasm. As a result many
daughter cells are formed.
(c) The cyst bursts to release the
daughter
cells
during
favourable conditions.
3. Budding :
Bud
Parent cell
2.
Ans.
3.
Ans.
296
Cyst
Multiple
formation fission
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Release of
daughter cells
during favourable
conditions
Daughter
cells
(a) Yeast reproduce by budding in which a small outgrowth is formed
on the parental cell.
(b) The nucleus of the parental cell divides and one daughter nucleus
migrates into the bud.
(c) The bud increases in size, separates and grows further.
Describe the human male reproductive system.
The human male reproductive system consists of :
1. Testis : Produces sperms (male
germ cells). As formation of sperms
Bladder
require temperature lower than
Seminal
the normal body temperature,
vesicle
testes are located outside the
abdominal cavity in the scrotum.
Prostate
gland
Testes secrete the hormone
Vas
testosterone which brings about
deferens
changes in boys during puberty.
Urethra
2. Epididymis : Immature sperms Epididymis
Testis
travel to the epididymis for
development and storage.
Penis
3. Vas deferens : It is a passage
through which the sperm travels
towards the urethra.
4. Seminal vesicle and prostate glands : They produce the ejaculatory
fluid which helps the sperm in transport and provides nutrition.
5. Penis : It is the portion of the reproductive system that delivers the
sperms to the site of fertilization.
6. Sperms : A sperm cell is composed of a head which carries the genetic
information, a middle part which carries mitochondria for energy
production and a tail which is like a flagellum to help in movement
towards the female germ cells.
Describe the human female reproductive system.
The human female reproductive system consists of main reproductive
organs like vagina, uterus, oviduct and ovaries.
1. Vagina :
(a) It is a muscular tube that extends from the vaginal opening to the uterus.
(b) It provides the route for the menstrual blood to leave the body
during menstruation.
(c) It is a pathway through which the sperms enter into the woman’s
body and is a pathway through which a baby comes out of the
woman’s body during childbirth.
SCHOOL SECTION
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Ans.
5.
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2. Uterus : Uterus is a muscular
Oviduct
organ. Due to strong muscles and
ability to expand and contract, the
uterus can accomodate a growing
foetus and push the baby during
Ovary Uterus
labour.
Endometrium
3. Overies : Ovaries are two oval
Cervix
shaped organs that lie to the upper
Vagina
right and left of the uterus. They
develop and release eggs into the
oviduct. They secrete hormone oestrogen which brings about changes in
girls during puberty. When a baby girl is born the ovaries already contain
thousands of immature eggs which remain inactive till maturity. On
reaching puberty, a woman’s ovaries usually release one egg each month.
Describe the process of fertilization, development and birth in human
beings.
1. The sperms enter through the vaginal passage, travel upwards and
reach the oviduct where they may encounter the egg.
2. As soon as it is fertilized, the egg cell (zygote) begins to divide until it
becomes a ball of cells called blastocyst.
3. The ball then implants itself in the wall of the uterus.
4. The development of the embryo takes place inside the uterus where
the embryo gets all the nutrients and oxygen from its mother’s blood in
the oviduct supplied through the umbilical cord.
5. From nine months onwards, the baby is ready to take birth. It moves
down.
6. During birth, the cervix gradually opens and the baby is released through
the vagina.
Write the functions of the following organs in reproduction.
*1. Vagina
*2. Stigma
*3. Ovaries
*4. Seminal vesicles and prostate glands
*5. Uterus
6. Epididymis
7. Vas deferens
8. Testis
9. Penis.
1. Vagina :
(a) It is a muscular tube that extends from the vaginal opening to the
uterus.
(b) It provides the route for the menstrual blood to leave the body
during menstruation.
(c) It is a pathway through which the sperms enter into the woman’s body.
(d) It is a pathway through which a baby comes out of a woman’s body
during child birth.
2. Stigma :
(a) It is the sticky terminal part of the style.
(b) It is the receptive organ on which pollen germinates.
3. Ovaries :
(a) Ovaries are two oval shaped organs which lie to the upper right
and left of the uterus.
(b) They develop and release eggs into the oviducts.
(c) They secrete hormone estrogen which brings about changes in
girls during puberty.
(d) When a baby girl is born, the ovaries already contain thousands of
immature eggs which remain inactive till puberty. On reaching
puberty, a woman’s ovaries usually release one egg each month.
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4. Seminal vesicle and prostate glands : They produce ejaculatory fluid
which helps the sperms in transport and provides nutrition.
5. Uterus :
(a) Uterus is a muscular organ.
(b) Due to strong muscles and ability to expand and contract, the uterus
can accomodate a growing foetus and can push the baby during labour.
6. Epididymis : Immature sperms travel to the epididymis for development
and storage.
7. Vas deferens : It is the passage through which the sperms travel towards
the urethra.
8. Testis :
(a) Produces sperms (Male germ cells).
(b) Testes secrete the hormone testosterone which brings about changes
in boys during puberty.
9. Penis : It is the portion of the reproductive system that delivers the
sperms to the site of fertilization.
Describe the changes that occur in boys and girls from childhood to
adulthood.
Ans.
Age
Rate of growth Changes in girls
From
Higher
birth
to age of
10-11
years.
11 to
age of
18 in
girls
and 21
in boys
(years).
1. Increase in
height.
2. Increase in
weight.
3. Acquire and
then loose
milk teeth
and again
acquire new
ones.
Rate of growth 1. Hair grows in
slows down and
armpits.
reproductive
2. Genital areas
tissues begin to
become darker
mature
in colour.
3. Skin becomes
oily and may
develop
pimples.
4. Breast size
begins to
increase
5. Begin to
menstruate.
Changes in boys
1. Increase in
Childhood
height.
2. Increase in
weight.
3. Acquire and
then loose milk
teeth and again
acquire new
ones.
1. Hair grows in
armpits and
genital areas.
2. Genital areas
become darker
in colour.
3. Skin becomes
oily and may
develop pimples.
4. Growth of
thicker hair on
face.
5. Voice begins
to crack.
Body is physically ready to reproduce.
Age 18
onwards
in girls
and 21
onwards
in boys
(years).
298
Stage
Puberty
(Frequent
emotional
shifts and
physical
maturation of
reproductive
system)
Adult
SCHOOL SECTION
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Q.VI
1.
Ans.
2.
Ans.
3.
Ans.
4.
Ans.
5.
Ans.
6.
Ans.
7.
Ans.
8.
Ans.
9.
Ans.
10.
Ans.
11.
Ans.
12.
Ans.
13.
Ans.
14.
Ans.
15.
Ans.
16.
Ans.
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Answer the following questions in one sentence each :
Which is the basic process in reproduction ?
A basic process in reproduction is the creation of a DNA copy.
Why is reproduction necessary?
Reproduction is necessary to maintain the number of individuals of a species
and to prevent their extinction.
Give one disadvantage and one advantage of asexual reproduction.
Lack of genetic variation is the disadvantage while rapid reproduction is
the advantage of asexual reproduction.
Name some animals and plants that reproduce asexually.
Animals such as Amoeba, Paramoecium etc. and plants like Spirogyra,
Bryophyllum, Mushroom, Sweet potato etc. reproduce asexually.
Name some plants which reproduce by vegetative propagation.
Plants which reproduce by vegetative propagation are Potato, Bryophyllum,
Sweet potato, etc.
What is animal cloning ?
Animal cloning is the process by which an entire organism is reproduced
in a genetically identical manner, from a single cell taken from the parent
organism.
Name the female reproductive part of a flower.
Carpel is the female reproductive part of a flower.
Name the male reproductive part of a flower.
Stamen is the male reproductive part of a flower.
Which are the main reproductive organs of the male reproductive
system?
Testes and Penis are the main reproductive organs of the male reproductive
system.
Name the main reproductive organs of the female reproductive system.
Vagina, Uterus, Oviduct and Ovaries are the main reproductive organs of
the female reproductive system
What is a blastocyst?
As soon as fertilization takes place, the egg cell (zygote) beings to divide
until it becomes a ball of cells called blastocyst.
Which day is observed and the World Population Day?
July 11 is observed and the World Population Day.
Give some examples of STDs.
Syphilis, Gonorrhoea, AIDS are some of the STDs.
Name some contraceptives.
Condoms, Oral pills, Copper-T are some of the contraceptives.
Name the agents of cross pollination.
The agents of cross pollination are wind, water or animals.
What is double fertilization ?
The second male gamete fuses with the secondary nucleus in the embryo
sac to form endosperm. This is called as double fertilization.
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ACTIVITY BASED QUESTIONS
ACTIVITY : 12.1
(a)
(b)
(c)
Q.
Ans.
Q.
Ans.
(d)
Observe the above pictures and answer the following questions :
Which life process is shown in the pictures ?
The life process reproduction is shown in the pictures.
Is it an essential life process like nutrition, respiration or excretion ?
Yes. It is an essential life process like nutrition, respiration, excretion
because it helps to maintain the number of individuals of a species and to
prevent their extinction.
ACTIVITY : 12.2
Q.
Observe the picture and identify the plants belonging to the same
species.
(a)
Ans.
(b)
(c)
(d)
(e)
(f)
Plants (b), (c), (d) belong to the same species as they look alike and have
similar structures of roots, stems and leaves.
ACTIVITY : 12.3
Q.
Ans.
300
Observe a permanent slide of amoeba showing binary fission under a
compound microscope.
1. Amoeba reproduces by simple binary fission.
SCHOOL SECTION
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Q.
Ans.
SCIENCE & TECHNOLOGY
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2. In this method, the parent cell of amoeba divides into two equal or
nearly equal parts and each part then grows into a new cell of amoeba.
3. The nucleus divides first followed by the division of cytoplasm by
constriction.
Allow some aquatic vegetation to decompose in a jar of pond water. In
this stagnant bacteria rich environment, paramoecium will often
multiply forming a ring just below the water surface. Observe them
under a microscope.
1. Paramoecium divides by transverse binary fission.
2. In the parent paramoecium cell, first the macronucleus divides.
3. A new oral groove is formed.
4. The two daughter cells separate.
5. Each daughter cell grows into a new paramoecium.
ACTIVITY : 12.4
Observe the following figures and classify them into transverse and
longitudinal binary fission.
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Macronucleus
dividing
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Q.
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Daughter
paramoecia
Binary fission in Euglena
Ans.
1. Paramoecium reproduces by transverse binary fission.
2. Euglena reproduces by longitudinal binary fission.
ACTIVITY : 12.5
•
•
•
•
Ans.
Buy a small packet of dry yeast.
Mix 1 gm of yeast, 2 gm of sugar and 25 ml of water in a beaker.
Keep the culture in a warm place.
After 2-3 hours, put a drop on a slide and observe the reproducing yeast
under a compound microscope.
1. Yeast cells show budding which is a method of reproduction.
2. In this method, a small outgrowth is formed on the parent yeast cell.
3. The nucleus of the parent yeast cell divides and one daughter nucleus
migrates into the bud.
4. The bud increases in size, separates and grows further.
ACTIVITY : 12.6
Q.
•
•
Ans.
Arrange the following plants and animals in ascending order with respect
to their structural complexity.
Plants : Bacteria, Sunflower, Fungus, Funaria, Spirogyra.
Animals : Frog, Amoeba, Planaria, Human being, Hydra.
Plants : Bacteria, Spirogyra, Fungus, Funaria, Sunflower.
Animals : Amoeba, Hydra, Planaria, Frog, Human being.
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ACTIVITY : 12.7
•
•
Q.
Ans.
Collect slimy green filaments from a pond.
Put one or two filaments on a slide.
Observe the slide under the microscope.
1. The filaments are of spirogyra.
2. The filament of spirogyra undergoes fragementation resulting in
numerous filaments.
3. With cell enlargement and subsequent mitosis, each fragment grows
and develops into a mature filament.
ACTIVITY : 12.8
Q.
Ans.
Observe the house lizard. If the tail of a house lizard is cut, the missing
part develops again from the remaining part of the tail.
1. House lizard has the capacity of regeneration.
2. Regeneration is carried out by specialised cells in lizard.
3. These cells proliferate and make large number of cells which later
develop into various cell types and tissues and help in the production of
the remaining part of the tail.
Underground
branch
(a)
(b)
(c)
ACTIVITY : 12.9
Q.
Ans.
Observe the figure and identify parts of the plants involved in
reproduction in each picture.
1. Picture (a) shows carrot. In carrot, reproduction occurs through roots.
2. Picture (b) shows leaf of Bryophyllum. In Bryophyllum, reproduction
occurs through leaves.
3. Picture (c) shows potato plant. In potato plant, reproduction occurs
through stems.
ACTIVITY : 12.10
•
•
Q.
Ans.
302
Take a piece of moist bread or chapati.
Leave it in a moist warm place for 2-3 days.
Observe the fungus grown on it.
1. The fungus grown on bread is bread mould(Mucor).
2. It shows thread like structures called hyphae.
3. The mould forms spores in the sporangium.
4. On maturity, the sporangium breaks open and releases spores.
5. When the spores land in a moist place, they germinate to form new
mould.
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ACTIVITY : 12.11
Complete the following table to get the difference between asexual and
sexual reproduction.
Characteristics
Asexual reproduction
Sexual reproduction
No. of parents
involved
One
Two
Type of cells
involved
Somatic cells
Germ cells
Type of cell
division
Mitosis
Meiosis at the time of
gametogenesis and mitosis after
fertilization.
Nature of
offspring
Identical to the parent
Different from parents
Rate of
reproduction
Rapid
Slow
Modes of
reproduction
Single cell divides to
form identical
daughter cells.
Two germ cells unite to form
zygote which further develops into
new offspring.
ACTIVITY : 12.12
•
•
•
Q.
Ans.
Go to your garden and pluck a shoe flower.
Bring it to your study room and open it taking care not to destroy its
various parts.
Carefully take out the petals, stamens, sepals and carpels.
Observe each one of them.
1. The petals are five in number. They are red in colour to attract insects
for pollination.
2. The stamen is the male reproductive part of a flower. It is made up of
two parts, anther and filament.
3. The sepals are green in colour present at the base of the flower. They
are together called as calyx. It protects the flower when it is in the bud
condition.
4. Carpel is the female reproductive part of the flower. It consists of three
parts, the basal swollen portion called ovary, an elongated part called
style and a sticky terminal portion called stigma.
ACTIVITY : 12.13
•
•
•
Try this in your garden.
You have to shake the anthers of a flower onto the stigma of another
flower to induce pollination between flowers of the same plant.
This type of pollination is called self pollination.
Horticulturists use a special kind of brush to transfer pollen between the
flowers of different plants.
This type of pollination is called cross pollination.
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ACTIVITY : 12.14
•
•
•
•
Ans.
Soak few seeds of green gram in water.
After 7-8 hours drain the excess water.
Keep the seeds in a wet cloth for a day.
Open a seed carefully and observe the different parts.
The different parts of the seed are seed coat, cotyledon, radicle and plumule.
ACTIVITY : 12.15
•
Q.
Ans.
Q.
Ans.
304
Observe the table showing human developmental stages (Page No. 277)
and answer the following questions :
During development which changes are common to both boys and girls ?
The following changes are common to both boys and girls during
development :
1. During childhood :
(a) Increase in height.
(b) Increase in weight.
(c) Acquiring and then losing milk teeth and again acquiring new ones.
2. During puberty :
(a) Hair grows in armpits and genital areas.
(b) Genital areas become darker in colour.
(c) Skin becomes oily and may develop pimples.
Why has the government of India legally fixed the minimum age of
marriage as 18 years for girls and 21 years for boys ?
The government of India has legally fixed the minimum age of marriage as
18 years for girls and 21 years for boys because at this age girls and boys
become adults and their bodies are physically ready to reproduce.
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HOTS QUESTIONS & ANSWERS
1.
Ans.
2.
Ans.
3.
Ans.
4.
Ans.
5.
Ans.
6.
Ans.
The reason for having attractive colours and fragrances of the flowers
is ...
(a) to get good price in the market.
(b) to give joy to others.
(c) to attract insects for the purpose of pollination.
(d) to attract human beings.
To attract insects for the purpose of pollination.
A father gave seeds to four of his sons and told them to convert seeds
into plants and bring the grown plants to show him after a period of
three months. None of his sons could fulfill his wish. What must be the
reason ?
Seeds develop into seedlings under appropriate conditions. Either the seeds
were damaged by boiling before they were given to the sons or the sons did
not plant them under appropriate conditions as a result of which the seeds
failed to develop into plants.
My neighbour gave birth to a twins. To our wonder, both the boys looked
similar to each other. How is that so ?
The sperms reach oviduct and encounter the egg. The egg cell or zygote, in
such case, gets split and separated into two parts during the early stage of
cell division. Each part then develops into a separate individual. As these
individuals are produced from a single zygote, they look similar.
Name those parts of the flowers which serve the same function as the
following do in the animals :
(a) Testes
(b) Ovary
(c) Eggs
(d) Sperms
(e) Fallopian tube.
(a) Pollen grain.
(b) Ovary.
(c) Female germ cell or egg cell.
(d) Male germ cells or gametes.
(e) Pollen tube.
A farmer plotted some seeds of a plant and also few branches of the
same plant in soil and provided appropriate conditions for them to grow.
Which method must have given the farmer flowers and fruits earlier
than the other ? Why ?
Plants produced by vegetative propagation take less time to grow and bear
flowers and fruits earlier than those produced from seeds. The branches
planted in the soil under favourable conditions must have borne flowers
and fruits earlier than the seeds.
A fish lays many eggs. A leopard gives birth to 2-3 cubs at a time. Why
is the difference ?
All animals want to make sure that their progeny should survive. Leopard
looks after its young ones till they become independent. If the number is
limited, it can do so. Fish do not look after their eggs or little ones. Therefore
they produce hundreds of eggs and leave them to develop by themselves.
Most of them die but because of the large number, a few succeed in
surviving.
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7.
Ans.
8.
Ans.
9.
Ans.
10.
Ans.
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Population size is an important factor in deciding the success rate of a
country. Why ?
There is undoubtedly a strong relation between high national fertility rate
and measures of poverty. As the population density increases, decrease in
per capita income and natural resources takes place. General health goes
down. It creates an economical burden on the nation.
Large families affect both the individual as well as community life. It gives
rise to economic pressure, poor health conditions, neglecting children,
poor housing, malnutrition, insufficient medical care, lack of better
education ultimately affecting the success of a nation.
What happens to the following parts of the flower after fertilization ?
(a) Egg cell
(b) Secondary nucleus in the embryo sac
(c) Zygote
(d) Ovule
(e) Ovary.
(a) One of the male gametes in pollen tube fuses with the egg cell to form
zygote.
(b) The second male gamete in the pollen tube fuses with the secondary
nucleus in the embryo sac to form endosperm.
(c) The zygote develops into embryo.
(d) The ovule develops into a seed.
(e) The ovary develops into the fruit.
Write the correlated term.
Amoeba : Simple binary fission :: Yeast : ................. .
Budding.
Describe binary and multiple fission with the help of figures.
Binary fission
Parent cell
Nucleus Cytoplasm Two daughter
dividing dividing
cells
Multiple fission
Cyst
formation
11.
Multiple Release of daughter
fission cells during favourable
conditions
Describe reduction (meiosis) and fertilization (mitosis) and a combination
of both with the help of ray diagram.
Ans.
Parent cell
2n
2n
2n
306
Two daughter cells
(restoring original
chromosomal number)
Mitosis
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Meiosis
n
Mitosis
Parent cell Reduction division
2n
Meiosis
(diploid)
n
n
n
n
Haploid
gametes
Mitosis
n
12.
Ans.
13.
Ans.
14.
Ans.
A scientist created a hen which was replica of a hen in his yard.
(a) What is the name of the process ?
(b) Give scientific reason for the process.
(c) Which was the first mammal to be created in this way ?
(d) Give one advantage of creating human beings in this way.
(e) Suggest some other name for this process.
(a) Cloning.
(b) Cloning is the process by which an entire organism is reproduced in a
genetically identical manner, from a single cell taken from the parent
organism.
(c) Dolly sheep.
(d) Brilliant or talented human beings could be created is the advantage.
(e) Duplicating, mirroring, replicating, imitating etc.
Dolly was the first cloned sheep.
She had three mothers but no father. From first mother diploid cell
having 2n chromosomes was selected. This cell was from udders of this
sheep. From second mother egg was taken out. The haploid nucleus of the
egg was removed by microsurgery. Now in this enucleated egg, diploid
nucleus from udder’s cell was inserted. This egg was then implanted in
the uterus of a third sheep which was called the surrogate mother. Then
one day Dolly was born. Later calf, monkey, cat, mice, etc. were also
cloned.
Questions :
(a) Who can be called the real mother of Dolly ? Why ?
(b) What is the meaning of surrogate mother ?
(c) Why had Dolly no father ?
(d) Which cell nucleus was used in cloning Dolly ?
(e) Which other animals have been cloned ?
(a) The sheep from whom the udder cell was taken can be called the real
mother of Dolly. Her diploid nucleus was taken, therefore, she is the
real mother of Dolly. Moreover, Dolly looked like her.
(b) Surrogate mother is the one which uterus is used for raising the foetus.
(c) Sperm was not used in cloning Dolly. Therefore, Dolly had no father.
(d) The udder’s cell nucleus was used in cloning Dolly.
(e) Sheep, calf, monkey, cat, mice, etc. are the other animals which have
been cloned.
What is the role of testosterone, glands like prostate and seminal vesicles
in the male reproductive system ?
(a) Testosteron is responsible for production of sperms. It is also responsible
for the development of secondary sexual characteristics in boys during
puberty.
(b) The glands like prostate and seminal vesicles produce the ejaculatory
fluid which helps in the transport of sperms and also provides nutrition.
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CONCEPT MAP
Type of
Life process
helps to
Reproduction
Prevent extinction
may be
Asexual
Sexual
involves
involves
One parent
Two parents
are
may be
Unicellular
Multicellular
Male
Female
produces
reproduce by
Male germ cell
Binary
fission
Multiple
fission
Budding
Regeneration
Egg
unite to form
Zygote
develops
into
reproduce by
Fragmentation
produces
Budding
Vegetative
propagation
Spore
formation
New
individual
Through
Root
Stem
Leaf

308
SCHOOL SECTION
S.S.C.
Marks : 20
CHAPTER 12 : THE LIFE CYCLE
Duration : 1 hr.
SCIENCE
Q.I
1.
2.
3.
[A] Fill in the blanks :
The functional unit in a plant’s sexual reproduction is ...................... .
The male reproductive part of a flower is ...................... .
Hydra uses regenerative cells for reproduction in the process of
....................... .
A basic process in reproduction is the creation of a ......................
copy.
2
Q.I
1.
2.
3.
4.
[B] Write the correlated terms :
Amoeba : Simple binary fission :: Paramoecium : ...................... .
Planaria : Regeneration :: Rhizopus : ...................... .
Root, Stem, Leaf : Vegetative propagation :: Flower : ...................... .
Asexual reproduction : Similarity :: Sexual reproduction :
...................... .
2
Q.I
1.
2.
3.
[C] Define the following :
Reproduction.
Vegetative propagation.
Meiosis.
3
Q.II
1.
2.
3.
4.
Draw a neat and labelled diagram : (Any Two)
Longitudinal section of flower.
Binary fission in amoeba.
Spore formation in Mucor.
Human female reproductive system.
4
Q.III
1.
2.
3.
4.
Answer the following questions : (Any Two)
Why does menstruation occur ?
Explain disadvantages of large family size.
Write a note on Regeneration.
Explain the importance of variation.
4
4.
Q.IV Answer the following : (Any One)
1.
Describe the human male reproductive system.
2.
Describe the modes of reproduction in unicellular organisms.
Best Of Luck 
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