Wednesday, January 2, 2013

CBSE Class 7 - Science - Reproduction in Plants

Reproduction in Plants
Concept Map on Reproduction of Plants
Flower image credits: wpclipart

NCERT Chapter Solution, Q & A

Q1:  Fill in the blanks

Answer:
(a) Production of new individuals from the vegetative part of parent is called_vegetative propagation_.

(b) A flower may have either male or female reproductive parts. Such a flower is called_unisexual flower_.

(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 _pollination__.

(d) The fusion of male and female gametes is termed as _fertilization___.

(e) Seed dispersal takes place by means of _wind__, __water_ and _animals_.

(f)  Asexual reproduction in spirogyra is an example of _fragmentation__.

(g) Mosses, Ferns, Moulds etc. reproduce by _spores___ formation.



Q2: Describe the different methods of asexual reproduction. Give examples.

Answer: Different methods of asexual reproduction are:
  1. Fragmentation: Parent body divides into distinct pieces which grow into new individuals. e.g. Spirogyra (an alga)
  2. Budding: A small part of parent body grows out as a bud which detaches and becomes a new individual. Sometimes a chain of buds is also formed. e.g. yeast, corals, sponges etc.
  3. Spores Formation: Parent plant releases thousands of tiny, spherical and unicellular spores which are protected by cell wall. When these spores find favourable environment, they grow into plants. e.g. mosses, ferns, moulds etc.
  4. Regeneration: Many plants like cacti, potato, rose, sugarcane etc. reproduce by this method. New plants are produced from vegetative parts of the mother plant such as root, stem or leaves.

Q3: Explain what you understand by sexual reproduction.

Answer: Plants that have flowers can reproduce sexually. A flower has male reproductive part called stamen and the female part is called pistil. A flower may be unisexual (containing one reproductive part only) or bisexual (containing both reproductive parts). Stamen has anther which produces male gametes called pollen grains. Pistil carries an ovary which produces female gamete called ovum. When mail gamete cells fuse together with female gamete cells, they form a zygote and this process is called fertilization. Later zygote transforms into a seed. Later seeds are dispersed to soil and under favourable conditions germinate into a new plant.

Q4: Explain the main differences between asexual and sexual reproduction.

Answer:

Asexual ReproductionSexual Reproduction
1. Only one parent is needed.1. Two parents or male and female gametes are required.
2. Offspring is genetically identical to its parent.2. Offspring exhibit variation with respect to its parents.
3. Fragmentation, Budding, Spore formation and vegetative
propagation are different ways to reproduce sexually.
3. Seeds are formed due to fusion of male and female cells.
4. Spirogyra, Yeast, moulds, potato exhibit asexual reproduction.4. Fruit bearing plants like mango, china rose reproduce sexually.


Q5:Sketch the reproductive parts of a flower.

Answer:
Structure of Flower


Watch the you tube video on structure of flowers.


Q6: Name the male part of the flower.

Answer: Stamen

Q7: Name the female part of the flower.

Answer: Psitil

Q8: What do you mean by pollination?

Answer: The process of transference of pollen grains from anthers to stigma is called pollination.

Q6: Explain the difference between self-pollination and cross-pollination.

Answer:
Self PollinationCross Pollination
1. Pollens are transferred to stigma of same flower.         1. Pollens are transferred to stigma of different flower.                             
2. Do not require pollinating agents.2. Requires Pollinating agents.
3. e.g. legumes,peanuts,sunflower2. Most flowers like rose, china rose.


Q7: How does the process of fertilisation take place in flowers?

Answer: After pollination, pollen grains start growing into a pollen tube passing through pistil.  The tube reaches the ovule and enter it. The pollen tube carries the male gametes. The male gametes fuses with the ova (female gamete) and forms a zygote. This process of fusion is called fertilization. Later zygote develops into an embryo. Meanwhile walls of the ovules develop into layers and form a seed. Thus a seed carries an embryo with stored food and is covered by a hard coating.


Q8: What are the different agents of pollination?

Answer: Different agents of pollination are:
  • Wind
  • Insect
  • Water

Q9: How seed is different from fruit?

Answer: A fruit is a mature ovary whereas ovule develops into a seed, which contains the developing embryo. A fruit can have one or many seeds inside it. e.g. A mango has one seed while a watermelon has many seeds.
Structure of Fruit
credits:wpclipart
Q10: Describe the various ways by which seeds are dispersed.

Answer: Same kind of plants grow at different places because seeds are dispersed to different places. Following are listed some agents of dispersal of seeds:
  1. Wind: For example seeds of cotton have hairs surrounding it which is carried by wind. Similarly seeds of maple has wings attached to it.
  2. Water: Coconut seeds which has thick fibre helps it float in water.
  3. Animals: Seeds like xanthium have spines which help them to stick to fur or skin of the animals. Some seeds eaten by birds and animals along with fruit pass out unharmed in waste. They germinate where they fall.
  4. Bursting of fruit: Fruits of Balsa, and pea burst on drying and spread the seeds in surroundings.
Q11:  Tick (✓) the correct answer

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


Q12: What are the advantages of Vegetative propagation?

Answer: Advantages of Vegetative propagation are:
  1. Plants produce by this method bear flowers earlier than the plants produced from seeds.
  2. Daughter plants are identical copies of their parent plant.
  3. This method is faster and help in growing plants in multiple numbers. e.g. used in horticulture to produce flowers of same kind for commercial purposes.
  4. Seedless plants can be produced.


3 comments:

  1. if i have understand i would say understand but i didn't understand

    ReplyDelete
  2. isn't it just woooooooooooooooow?

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  3. This comment has been removed by the author.

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