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Chapter 12 Reproduction in Plants

  • The parents give birth to their young ones which are similar to them is called reproduction.
  • Reproduction is of types. Vegetative, sexual and asexual.
  • Vegetative is the part of asexual reproduction.
  • Root, stem, leaves are the vegetative parts of the plants.
  • The reproduction in which only parent are involved is known as asexual reproduction.
  • In plants reproduction occur in flower. Flower has reproductive parts.
  • A small outgrowth appear on the plant is called as budding.
  • Asexual reproduction occur in many ways like budding, fragmentation, spare formation etc.
  • The reproduction in which part of the plant in divided into two is known as fragmentation.
  • Spares are tiny asexual reproductive bodies.
  • The reproduction which occur due to the formation of spares known as spare formation method of asexual reproduction.
  • Unisexual flowers are those in which only are reproductive part is present either male or female.
  • Bisexual flowers are those in which both male and female reproductive parts are present.
  • Stamen is the male reproductive part of the plant which contain Anther and filament.
  • The male and female reproductive cells are called gamete.
  • Male gamete is produced by pollen grain which is inside the anther.
  • The female gamete or the egg is formed in an ovule.
  • The process of fusion of male and female gamete is called fertilization.
  • Hypha is a long thread or branch like structure which forms the body of the fungus.
  • Ovule contains egg or female gametes which is the part of the ovary.
  • When a pollen grain lands on the stigma of a flower, it grains in a tube, this tube is called as pollen tube.
  • The transfer of pollen from the anther to the stigma of a flower is called pollination.
  • Movement or transport of seeds away from the plant by means like wind, air and water is called seed dispersal.
  • By the fusion of male and female gamete a cell is formed known as zygote.
  • After development of zygote, embryo is formed.

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Download pdf of NCERT Examplar with Solutions for Class Science Chapter 12 Reproduction in Plants

Exercise 1 ( Page No. : 141 )

  • Q1

    Fill in the blanks:

    (a) Production of new individuals from the vegetative part of parent is called_____________.
    (b) A flower may have either male or female reproductive parts. Such a flower is called_____________.
    (c) The transfer of pollen grains from the anther to the stigma of the same or of another flower of the same kind is known as _____________.
    (d) The fusion of male and female gametes is termed as _____________.
    (e) Seed dispersal takes place by means of _____________, _____________ and _____________.

    Ans:

    (a) Vegetative propagation
    Vegetative propagation is an asexual method of reproduction in plants in which lower plants reproduce vegetatively through various methods like budding, fission, fragmentation, spores, buds etc. With the flowering parts roots, stems, leaves and buds helps in the vegetative propagation. For example: tuberous roots of modified plants can be vegetatively propagated when planted in soil.

    (b) Unisexual
    A flower may have either male or female reproductive parts. Such a flower is called unisexual flower whereas bisexual flower possess both stamen (male reproductive organ) and pistil. 

    (c) Pollination
    The transfer of pollen grains from the anther to the stigma of the same or of another flower of the same kind is known as pollination. This is of two types: self- pollination (it involves the transfer of pollen grains from the anther to the stigma of the same flower) and cross- pollination (it involves the transfer of pollen grains from the plant of one flower to the stigma of another plant).

    (d) Fertilization
    The process in which the male gamete fuses with the female gamete that is present in ovule to form a new cell called diploid zygote is called fertilization that occurs within the embryo sac or female gametophyte.

    (e) Air, water and insects
    Seed dispersal takes place by various agent that is responsible for cross pollination. Anemophily (wind pollination) is the mode of transfer of pollen grains from anther to stigma through the agency of wind. Hydrophily is the water pollination in which the transfer of pollen grains from anther to stigma occurs through the agency of water. Wind and water pollination both are the abiotic factors of the pollination. Entomophily is the animal pollinator or biotic category in which the transfer of pollen grains from anther to stigma occurs through the agency of insects like moths, flies etc.


    Q2

    Describe the different methods of asexual reproduction. Give examples.

    Ans:

    Asexual reproduction is the simplest form of reproduction in which only one parent is involved. It do not involves the meiosis, gamete formation and fusion of gametes. This asexual reproduction is also known as clonal propagation because of their genetically identical products.

    The asexual reproduction in plants can take place by the following methods:

    1. Vegetative propagation: It is the natural process that is found in many plant species. It is a process by which plant reproduces without the production of seeds and spores. In this growth of new plants from the plant parts (like bulbs, runners, stems cuttings, roots and leaves etc.) occurs. Tissue culture is also the method of vegetative propagation under the sterile conditions.

    Examples: Tuber of potato, the rhizome of ginger etc.

    2. Budding: In budding process a small part of the body of the parent plant grows as a bulb- like structure called ‘bud’ which then detaches and becomes a new plant or we can say formation of daughter individual from the small projection called the bud that arises on the parent body is known as budding.

    Example: Yeast (unicellular fungi), Hydra etc.

    3. Fragmentation: The breaking up of the body of a plant into two (or more) pieces on maturing, each of which automatically grows to form a new plant, is called fragmentation. An alga reproduces by the asexual method of fragmentation. An example of common alga is Spirogyra. Spirogyra is a green, filamentous alga plant which is found in ponds, lakes and slow moving streams. Spirogyra reproduces by the asexual method of reproduction called fragmentation.

    4. Spore Formation: Propagules which germinate to produce new individuals are known as spores. There are several types of spores: zoospores, sporangiospores, chlamydospores, oidia and conidia.  


    Q3

    Explain what you understand by sexual reproduction.

    Ans:

    Sexual Reproduction:  Meiosis and fertilization; these two are the essential processes in the sexual cycle of the flowering plants Sexual reproduction is the combination of reproductive cells from two individuals to form offspring (with unique characteristics). Sexual reproduction produces offspring with the different combination of genes and as a result it leads to evolution with the new characteristics. It includes the production of gametes which have half the number of chromosomes compared to all other cells in the organisms.

    Most of the flowering plants reproduces through the sexual reproduction method involving the fusion of sex cells called gametes. This means that two sexes: male and female that are involved in reproduction in flowering plant. Flowers are the reproductive part of the plant. The sexual reproduction in plants involves the fusion of male and female gametes of the plants which leads to the formation of the seeds of the plant and these seeds can then used to grow new plants.


    Q4

    State the main difference between asexual and sexual reproduction.

    Ans:

     

                Asexual Reproduction            Sexual Reproduction
    1. It does not involve gametes formation. 1. It involves gamete formation.
    2. Offspring will be genetically identical to its parents. 2. Offspring will be genetically identical to the different parents.  
    3. No fertilization occurs. 3. Fertilization takes place.
    4. Characteristics of only one parent are inherited. 4. Characteristics of both parents are inherited.
    5. Multiplication is very rapid and takes less time.

    5. Multiplication is not so rapid and takes a longer time to complete.

    6. The number of offspring produced in various forms. 6. The number of offspring produced in lower amount comparatively. 
    7. No evolutionary occurs.  7. Evolution takes place by the mutation. 
    8. Bacterial fission, fragmentation, spore formation, budding or agamospermy are different types of asexual reproduction. 8. Sexual reproduction occurs through the formation of sexual spores. 

     


    Q5

    Sketch the reproductive parts of a flower.

    Ans:

     

            flower

    A flower is modified into complex shoot to carry out sexual reproduction in the higher plants. The terminal or the end part of the axis of the flower that supports all the floral appendages: sepals, petals, stamens and carpels; is known as receptacles. These four whorls of floral appendages attached on the receptacle in which the two lower whorls (calyx and corolla) are sterile; and upper two are (androecium and gynoecium) are fertile or reproductive whorls. The floral parts are explained as below:  

    1. Calyx: It is the outermost circle of a floral leaves are called calyx and the individual leaf segment is known as sepal, is green in colour. The function of sepals (Or calyx) is to protect the flower in its starting stages when the bud formation occurs.

    2. Corolla: This is the second whorl of the floral leaves arise from the inner part to the calyx, and colourful parts of a flower are called corolla and the individual leaf of corolla is known as Petal. The petals lie inside the sepals and are generally coloured which attracts the insects (for pollination) and to protect the reproductive organs of the flower.

    3. Androecium: The little stalk and the third whorl of the floral appendage that arises inner to corolla; individual appendage is stamen. Stamen is the male reproductive organ of the plant and consists of two parts: a filament and an anther. The stalk of stamen is called filament and the swollen top of stamen is called anther and it makes the pollen grains and stores them. Pollen grains appear to be yellow, powder like substance to us. Pollen grains contain the male gametes (or male sex cell) of the plant which is present inside a pollen grain is called ‘male nucleus of pollen grain’.

    4. Gynoecium (or pistil): In the centre of a flower, there is a flask-shaped organ called pistil and it represents female reproductive organ of the plant. A pistil is constitutes of three parts: stigma, style and ovary. Ovary is the present on the base and is swollen part of the carpel that bears various ovules. Stigma lodges pollen grains. Style is the connection between ovary and stigma.


    Q6

    Explain the difference between self-pollination and cross-pollination.

    Ans:

    Pollination is the transfer of pollen grains from the anther to the stigma of the flower which can be achieved by biotic (insects, birds etc.) and abiotic (wind, water etc.) pollinating agents. On the basis of pollinating mechanism, plants can be grouped into two mating systems: self- pollinated and cross- pollinated.

               Self- Pollination               Cross Pollination
    1. The pollen grain moves to the female part of the same flower or different flower of the same plant species.  1. The pollen grains are transferred to the flower present on the different plant. 
    2. Transfer to the same flower is autogamy; and to another flower on the same plant is geitonogamy. 2. Cross- pollination is also known as allogamy.
    3. No genetic variation occurs. 3. High genetic variation are found. 
    4. Identical species are created, i.e. no new species are formed. 4. New species are formed.
    5. Transfer of pollen grains are limited.  5. Transfer of pollen grains unlimited, i.e. in large amount. 

     


    Q7

    How does the process of fertilisation take place in flowers?

    Ans:

    The process of fusion of gametes of male and female (egg) to form the diploid zygote in the embryo sac is called fertilization.

    Fertilization takes place as follows: The pollen generally germinates on the stigma. When a pollen grains falls on the stigma of the pistil then the pollen grains grows a pollen tube into downward direction through the style towards the female gametes in the ovary. A male gamete are carried to the egg by the pollen tube and enters the ovule in the ovary. The tip of pollen tube bursts out and male gametes comes out of pollen tube or gets spreads out. In ovary, the male gametes of pollen fuses with the female gamete present in ovule to form the ‘zygote’ then zygote develops into the embryo sac; this process is known as siphonogamy. Embryo is that part of a seed that develops into the new plant.


    Q8

    Describe the various ways by which seeds are dispersed.

    Ans:

    Seed dispersal takes place by various agent that is responsible for cross pollination; and this means to scatter seeds over a large area. The seeds of some of the plant disperse as seeds and some are dispersed in the form of fruits because they contain seeds inside them. There are various methods of seed dispersal that have been categorised into two main categories: Abiotic (like wind, gravity, water etc.) and Biotic (animal pollinators like insects).

    Anemophily (wind pollination):                                                                                                                                                                                                      It is the mode of transfer of pollen grains from anther to stigma through the agency of wind. The flowers that are wind pollinated are anemophilous. These flowers contains some adaptations like flowers are colourless, odourless and nectar-less; pollen grains are small, dry, dusty and sometimes saccate so that they can blow away easily to the long distances etc.

    Hydrophily (water pollination):                                                                                                                                                                                                      It is the mode of transfer of pollen grains from anther to stigma occurs through the agency water. The flowers that are water pollinated are hydrophilous flowers. These flowers contains some adaptations like flowers are small, colourless, odourless and nectar-less; pollen grains are unwettable, stigma are long and sticky etc. Dispersal by water takes place in some aquatic plants which is very rare and in some that grows near a water body. For example: Zostera, Hydrilla, Ceratophyllum etc.

    Entomophily (insects pollination):                                                                                                                                                                                                It is the animal pollinator or biotic category in which the transfer of pollen grains from anther to stigma occurs through the agency of insects. The flowers that are insect pollinated are entomophilous flowers. These flowers contains some adaptations like flowers are usually large, brightly coloured and slowly to attract insect pollinators etc. The most common insect pollinators are as follows: moths, flies, butterflies, bees, beetles etc.

    Dispersal by Humans: Human beings also help in dispersal of seeds during the farming.                                                                                                          

    There are much more methods for the dispersal of seeds like Ornithophily (pollination by birds), Chiropterophily (pollination by bats) etc.  


    Q9

    Match items in Column I with those in Column II:

    Column I                             Column II
    (a) Bud                                  (i) Maple
    (b) Eyes                                (ii) Spirogyra
    (c) Fragmentation                 (iii) Yeast
    (d) Wings                              (iv) Bread mould
    (e) Spores                             (v) Potato
                                                  (vi) Rose

    Ans:

    Here are the correct matches; 

    Column I                             Column II
    (a) Bud                                  (iii) Yeast
    (b) Eyes                                (v) Potato
    (c) Fragmentation                 (ii) Spirogyra
    (d) Wings                              (i) Maple
    (e) Spores                             (iv) Bread mould

    Budding is a process of asexual reproduction in which bud is arise from the parent body and when it mature, it get detached from the parent body and makes a new individual. Eyes (as bud) potato's vegetative part that also shows budding process. fragmentation is the asexual mode of reproduction. spirogyra is an algae which shows reproduction through this fragmentation method. Maple have seeds which have wings, which is very light weighted so that pollination is being easy or the transfer of pollen grains from anther to stigma is easy. Bread mould is the most common fungi, found in tropical and sub- tropical regions. Spores are asexual reproductive bodies, are light in weight and covered by hard protective covering which protects them from unfavourable condition like high temperature and low humidity.  
                                                 


    Q10

    Tick the correct answer:

    (a) The reproductive part of a plant is the
    (i) leaf    (ii) stem    (iii) root    (iv) flower

    (b) The process of fusion of the male and the female gametes is called
    (i) fertilisation          (ii) pollination
    (iii) reproduction      (iv) seed formation

    (c) Mature ovary forms the
    (i) seed                   (ii) stamen
    (iii) pistil                  (iv) fruit

    (d) A spore producing plant is
    (i) rose                   (ii) bread mould
    (iii) potato              (iv) ginger

    (e) Bryophyllum can reproduce by its
    (i) stem                  (ii) leaves
    (iii) roots                (iv) flower

    Ans:

    (a); (iv) Flower                                                                                                                                                                                                                              Flowers are the reproductive part of a plant that contains Stamens and pistils which are the male and the female reproductive part of a plant respectively.

    (b); (i) Fertilization
    The process of fusion of gametes of male and female (egg) to form the diploid zygote in the embryo sac is called fertilization.

    (c); (iv) Fruit
    Ovary contains ovules that develop into seeds after the fertilization process. After that the zygote differentiates to form an embryo sac inside the ovule. The ovary matures to turn into the fruit which can either be fleshy or dry, in which the seeds are embedded in them. A fruit is mainly formed as the result of cell division, expansion and differentiation in the ovary; or the results of stimuli received from pollination as well as from the seeds that are developing. 

    (d); (ii) Bread mould
    Spore is a unit of reproduction in plants which may also be used for dispersal as well as for survival in unfavourable conditions spore- producing plants include ferns, mushroom, liverworts, hornworts and mosses etc.

    (e); (ii) Leaves
    Bryophyllum is a group of plant species of the family Crassulaceae and can reproduce by its leaves, i.e. reproduces asexually.


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