WBBSE Class 10 Life Science Solutions Chapter 2C Sexual Reproduction in Flowering Plants

Detailed explanations in West Bengal Board Class 10 Life Science Book Solutions Chapter 2C Sexual Reproduction in Flowering Plants offer valuable context and analysis.

WBBSE Class 10 Life Science Chapter 2C Question Answer – Sexual Reproduction in Flowering Plants

Short Answer Type Questions : 2 Marks

Question 1.
Define asexual and sexual reproduction.
Answer:
Asexual Reproduction : It is a type of multiplication in which a young one is formed from a specialized or unspecialized part of a parent without the formation and fusion of sex cells, gametes.
Sexual Reproduction : It is a type of reproduction which takes place by the formation and fusion of gametes. It involves two major processes;
(a) Meiosis (reductional division) by which diploid sporophytic cells give rise to haploid gametes and
(b) Fertilization, which reconstitutes the sporophytic diploid generation through gametic fusion.

Question 2.
What are the two kinds of pollination?
Answer:
Two Kinds of pollination-
i. Self pollination : It is the transfer of pollen from the anther to the stigma of the same flower or to the stigma of another flower of the same plant.
ii. Cross-pollination : It is the transfer of pollen from the anther of flowers of the one plant to the stigma of a flower of another plant.

Question 3.
Define the term unisexual and bisexual giving one example of each.
Answer:
Unisexual Organism : Male and female sex organs are present in different individuals. Such organisms are called unisexual. Example- Human.
Bisexual organism : Single individual having both male and female sex organs. Examples: Most of the plants, Tapeworm, Earthworm.

Question 4.
Mention the reproductive parts of a flower.
Answer:
Reproductive parts of a flower :
Stamens : It consists of stalk and a flattened top called anther. Anthers produce pollen grains. The pollen grains produce two male gametes.
Carpels : It has a swollen ovary at the base and an elongated middle style and terminal stigma. The ovary contains, ovules. Each ovule has an egg or female gamete.

Question 5.
Differentiate ovule and ovary.
Answer:
Ovule : A structure in the ovary of a plant that develops into a seed after fertilization.
Ovary : The enlarged basal portion of a pistil that bears the ovules in angiosperms.

Question 6.
What are the ways in which pollination happens?
Answer:
Pollination may happen in any of the following ways :

1. The pollen of the same flower may fall on its stigma by itself.
2. The pollen of another flower of the same plant may fall on the stigma.
3. The pollen of a flower of another plant of the same species may land on the stigma. This transference can occur through wind, insects or other agents.

Question 7.
Where do the molds on bread come from?
Answer:
The spores of the molds are present in the air. The spores of the molds under suitable conditions settle on the bread and grow.

Long Answer Type Questions : 5 Marks

Question 1.
Draw the chart for the fertilization of flowering plant.
Answer:

Question 2.
What do mean by Pollination?
Answer:
Pollination is the process of transfer of pollen grains from the anther to the stigma of a flower, it is of two types :
(i) Self-pollination : If the pollen grains from the anther of a flower are transferred to the stigma of the same flower, it is termed as self-pollination or autogamy (auto : self; gamy: marriage), e.g. pea and china rose.

(ii) Cross-pollination : If the pollen grains from anther of one plant reach the stigma of a flower on another plant of the same species, then this is called as cross-pollination or allogamy (alias: other; gamy: marriage). Cross-pollination has the advantage of increasing the chances of variations.

Question 3.
Write a short note on asexual and sexual reproduction in plant.
Answer:
ASEXUAL : DNA is identical to the parent (clones). Plants use this method naturally, they have developed special structures for asexual “propagation.” Bulbs, rhizomes, tubers, corns, runners are all structures that can form new plants identical to the parent.

SEXUAL : DNA from male (sperm) and female (egg) is recombined to produce offspring genetically different than the parents. Flowers develops as the sexual structures in flowering plants. Egg and sperm come together (egg is fertilized) to produce seeds.

Question 4.
Mention different parts of flower with their role.
Answer:
Parts of a flower :
Stamen : Male part, Anther : produces pollen (sperm), Filament : positions anther,
Pistil : Female part, Stigma : traps pollen (sperm), Style : positions stigma, Ovary : produces egg cells, develops into fruit, Egg cells : get fertilized by sperm develops into seeds.

Question 5.
How pollination occurs in flowering plants?
Answer:
Pollination: “Pollen landing on the stigma of a pistil”- The first step in the development of seed.
Reasons for Pollination methods :

1. Sperm must travel to the egg (Pistil) of a flower
2. Plants’ movement is limited
3. Must use other methods to move pollen

Methods : Animal Wind

Question 6.
What are the adaptations required for animal and wind pollination?
Answer:
Adaptation for Animal Pollination :
i. Size and Colour of petals :
Red colour attracts some birds, like Humming birds. White colour flowers open at night and moths are attracted.
Pattern of petals sometimes reflects UV light and helps the insects where to land.
ii. Fragrance of flowers :
Sweet : some animals are attracted like bees.
Rotten : Some animals like flies are attracted.
iii. Nectar : contains sugar water which helps in pollination.
Adaptations for Wind Pollination :

1. Lack of petals : Energy is not spent on producing petals
2. Lack of Fragrance : Energy is not spent on producing these chemicals
3. Lack of Nectar : Energy is not spent on producing sugars
4. Lots of pollen : Only by chance that pollen lands on the stigma, produces lots of pollen to increase lots of success
5. Modification of stigma : Large, Feathery, Sticky- all to increase chance of catching pollen.

Question 7.
Write the various steps involved in the formation of a plant seed, starting from pollination.
Answer:
The transfer of pollen grains from anther to stigma is called pollination. The stamens in flower have anthers which produce pollen grains. Gynaecium or pistil bears three parts ovary, style and stigma. After pollination pollen grains form pollen tubes. Inside the pollen tube the nucleus divides into vegetative nucleus and generative nucleus. This generative nucleus gives rise to two male gametes inside the pollen tube. Pollen tube after piercing through the style reaches the ovary. One of which fuses with egg to form zygote. The second male gamete fuses with two polar nuclei to form triploid endosperm nucleus which finally gives rise to endosperm. So, the higher plants (angiosperms) show the process of double fertilization.

Soon after fertilization the petals, stamens, stigma and style fall off. The sepals wither and hold on to the ovule. The zygote, divides in a fixed fashion to form embryo. It may bear one or two cotyledons. An embryo axis made up of plumule and radicle. Radicle gives rise to root and plumule to shoot after germination of seed. Cotyledons contain food reserve.

Question 8.
Explain the different parts of the flower with the help of a labelled diagram.
Answer:
A complete flower contains sepals, petals, androecium or stamen and gynoecium or carpel or pistils. Sepals are green in colour and protect the flower in bad condition. Petals are large and variously coloured to attract insects for pollination. Stamen is the male reproductive part. It consists of two parts-a long narrow stalk like filament and anther. The anther lobes consist of pollen sacs that contain millions of pollen grains. The male gametes are produced inside the pollen grains.

A pistil is the female reproductive part and consists of a swollen stigma at the top, a slender tube like style and a swollen ovary at the bottom. Inside the ovary, ovules are present which contain embryo sac. The unripe seed or eggs are present inside this sac.

Question 9.
Describe the various post fertilization changes in flowers.
Answer:
Various post fertilization changes in flowers are :
(a) Bright colour of flower is lost.
(b) Except ovary, all the parts of flower fall off.
(c) Ovules in the ovary supplies food to the zygote which becomes embryo.
(d) Meanwhile, the walls of ovules become hard.
(e) Thus, the ovule transforms itself into seed.
(f) As the seeds form, the ovary increases in size and becomes fruit.
(g) The ovary wall becomes fruit wall.

Question 10.
Discuss the three different methods of vegetative propagation. Give suitable examples to support your answer.
Answer:
When new plants are produced from parts of the parent plant such as the root, stem or leaves, without the help of any reproductive organs, the process is known as vegetative propagation. Three types of vegetative propagation are:
(a) Vegetative propagation by stem : Aerial weak stems like runners and stolons, when they touch the ground, give off adventitious roots. When the connection with the parent plant is broken, the portion with the newly struck roots develops into an independent plant. Example-Some species of grass and strawberry. Underground stems can also produce several new plants from their buds. Example : Tuber of potato, bulb of onion.

(b) Vegetative propagation by root : Roots also help in vegetative propagation. For example, dahlia and sweet potato have roots that help in vegetative propagation. Root tuber of sweet potato grow into a new plant when sown in well prepared soil. Weeds like dandelion are capable of regenerating into a new plant, if some parts of its root are left behind in the soil.

(c) Vegetative propagation by leaves : It can be seen in very few plants like bryophyllum and begonia which are produced from leaves. They have buds on the notches in their margins. These buds, after falling on the ground or coming in contact with the soil, grow into new plants.

Multiple Choice Questions : 1 Mark

Question 1.
Flowers with both Androecium and the Gynoecium are called
(a) Anthers
(b) Stamens
(c) Bisexual flowers
(d) Unisexual flowers
Answer:
(c) Bisexual flowers

Question 2.
Flowers with either the Androecium or the Gynoecium are called
(a) unisexual flowers
(b) Stigma
(c) Anther
(d) Bisexual flowers
Answer:
(a) unisexual flowers

Question 3.
Which of the following have unisexual flowers?
(a) Papaya
(b) Coconut
(c) Palm
(d) All of these
Answer:
(d) All of these

Question 4.
The Anthers of the stamens when ripe produce fine dust like particles called
(i) Sperms
(b) Egg Cells
(c) Stigma
(d) Pollen grains
Answer:
(d) Pollen grains

Question 5.
The transfer of pollen grains from the anther to the stigma of a flower is known as
(a) Fertilization
(b) Pollination
(c) Diffusion
(d) Adoption
Answer:
(b) Pollination

Question 6.
The pollen grains of a flower are transferred to the stigma of the same flower in
(a) Diffusion
(b) Cross Pollination
(c) Self pollination
(d) Fertilization
Answer:
(c) Self pollination

Question 7.
Self pollination occurs in plants like
(a) Wheat
(b) Tobacco
(c) Peas
(d) All of these
Answer:
(d) All of these

Question 8.
Cross pollination takes place in
(a) Tomato
(b) Hibiscus and Lady Finger
(c) Brinjal
(d)All of these
Answer:
(d)All of these

Question 9.
Which of the following helps in cross pollination in unisexual flowers?
(it) Wind
(b) Bees
(c) Butterflies
(d) All of these
Answer:
(d) All of these

Question 10.
Pollination by wind takes place in Maize, Paddy and grass
(a) Maize
(b) Paddy
(c) Grass
(d) All of these
Answer:
(d) All of these

Question 11.
In Vallisneria, Hydrilla pollination takes place by
(a). Wind
(b) Water
(c) Insects
(d) All of these
Answer:
(d) All of these

Question 12.
Flowers like night queen, Jasmine emit a sweet scent to attract insects like
(a) Honey bees
(b) Butterflies
(c) Beetles and moths
(d) All the above
Answer:
(d) All the above

Question 13.
The fusion of the male reproductive nucleus and the female reproductive nucleus is called
(a) Fertilization
(b) Adoption
(c) Regeneration
(d) Excretion
Answer:
(d) Excretion

Question 14.
At the end of pollen tube there are two nuclei called
(a) Sperm and Ovum
(b) Tube nucleus and generatvie nucleus
(c) Tube nucleus and Sperm
(d) Generative nucleus and Stigma
Answer:
(b) Tube nucleus and generatvie nucleus

Question 15.
Which of the following are the two nuclei inside the embryo sac
(a) Egg cell and Secondary nucleus
(b) Micropyle and Egg cell
(c) Stamen and Stigma
(d) Anther and style
Answer:
(a) Egg cell and Secondary nucleus

Question 16.
The tip of the pollen tube breaks when the pollen tube passes into the ovule through
(a) Micropyle
(b) Embryo
(c) Calyx
(d) Corolla
Answer:
(a) Micropyle

Question 17.
The zygote develops into
(a) Pedicel
(b) Embryo
(c) Stigma
(d) Style
Answer:
(b) Embryo

Question 18.
One of the male nuclei fuses with the egg cell and forms
(a) Stigma
(b) Pedicel
(c) Corolla
(d) Zygote
Answer:
(d) Zygote

Question 19.
One of the nucleus of the pollen tube fuses with the secondary nucleus of the ovum and grows into
(a) Stamen
(b) Stigma
(c) Anther
(d) Endosperm
Answer:
(d) Endosperm

Question 20.
Generative nucleus divides forming
(a) Three female nuclei
(b) Two male nuclei
(c) Three male nuclei
(d) Two female nuclei
Answer:
(b) Two male nuclei

Question 21.
The number of outer layers present in each ovule are
(a) 2
(b) 3
(c) 4
(d) 5
Answer:
(a) 2

Question 22.
At the upper end of the outer layer there is an opening known as
(a) Stigma
(b) Style
(c) Micropyle
(d) Anther
Answer:
(c) Micropyle

Question 23.
Embryo sac is present inside the
(a) Ovule
(b) Stigma
(c) Micropyle
(d) Style
Answer:
(a) Ovule

Question 24.
The number of nuclei present inside the embryo sac are
(a) 4
(b) 2
(c) 5
(d) 3
Answer:
(b) 2

Question 25.
Pollen from one flower is carried to the stigma of another flower of the same plant or a different plant of same species in
(a) Self pollination
(b) Cross pollination
(c) Fertilization
(d) Diffusion
Answer:
(b) Cross pollination

Very Short Answer Type Questions : 1 Mark

Question 1.
Name the reporductive whorls of flowering plants.
Answer:
Male sex organ : Stamens
Female sex organ : Carpels.

Question 2.
Name the elements of egg apparatus.
Answer:
Egg nucleus, definitive nucleus, synergids, antipodal cells.

Question 3.
Give example for self and cross pollination
Answer:
Self pollination : Vinca
Cross pollination : Cucurbita

Question 4.
Give examples of the following : Anemophilous, Hydrophilous. Entomophilous, Ornithophilous Plant
Answer:

• Anemophilous : Paddy flower
• Hydrophilous : Ceratophyllum
• Entomophilous : Mangifera indica
• Ornithophilous : Erythrina

Question 5.
What are synergids ?
Answer:
There are three nuclei adjacent to micropyle. Out of these three nuclei, the central one is egg and other two nuclei are known as synergids.