Class 9 SELINA Solutions Biology Chapter 5: Pollination and Fertilization
Pollination and Fertilization Exercise Ex. 1
Solution A.1(a)
(ii) Pollen grain
Solution A.1(b)
(iii) Stigma and anthers mature at the same time
Solution A.1(c)
(ii) Autogamy
Solution A.1(d)
(i) Homogamy
Solution A.1(e)
(iii) Ornithophily
Solution A.1(f)
(iii) Bignonia
Solution A.1(g)
(iii) Insects
Solution A.1(h)
(iii) Tassel
Solution A.1(i)
(i) Pea plants
Solution A.1(j)
(i) Generative nucleus
Solution B.1
(a) butterflies
(b) wind
(c) water
Solution B.2
(a) Transfer of pollen grains from anthers to stigma of the same flower is called autogamy.
(b) Different timings for maturation of gynoecium and androecium is called dichogamy.
(c) Vallisneria is a water-pollinated flower.
Solution B.3
|
Column A |
Column B |
|
(a) Generative nucleus |
(v) Male nuclei |
|
(b) Germ pore |
(i) Pollen tube |
|
(c) Exine |
(vi) Rough |
|
(d) Secondary nucleus |
(ii) Endosperm nucleus |
|
(e) Integument |
(iii) Testa |
|
(f) Egg nucleus |
(iv) Fertilization |
Solution B.4
(a) Ovules
(b) Ovary
(c) Ovarian wall
Solution B.5
(a) Bisexual flower
(b) Inflorescence
(c) Self-pollination/Autogamy
(d) Dichogamy
(e) Heterostyly
(f) Entomophily
(g) Ornithophily
Solution C.1
(a) Ornithophily-Pollination affected by birds
(b) Elephophily-Pollination affected by elephants
(c) Artificial pollination-Pollination affected by man through artificial means
Solution C.2
(a) Pollination: Pollination is the process of transfer of pollen grains from the anther to the stigma of a flower.
(b) Herkogamy: Herkogamy is a condition in which the pollen of a flower fails to reach the stigma of the same flower due to a mechanical or structural barrier.
(c) Cleistogamy: Cleistogamy is a condition in which certain bisexual flowers remain closed even at maturity and their reproductive structures remain hidden and lie close to each other, thereby facilitating self-pollination.
(d) Emasculation: Removal of anthers in young flowers is termed as emasculation.
(e) Fertilization: Fertilization is the union/fusion of the nuclei of male and female gametes.
Solution C.3
(a) Ovules-Seed
(b) Calyx-Falls off or remains intact in dried and shrivelled form
(c) Petals-Fall off
(d) Stamens-Fall off
Solution C.4
Contrivances in flowers which favour cross-pollination:
1. Unisexuality
2. Different timings of maturation of androecium and gynoecium
3. Self-sterility
4. Structural barriers
Solution D.1
(a) Differences between Autogamy and Geitonogamy:
|
Autogamy |
Geitonogamy |
|
The pollen of the same flower may fall on its stigma by itself. |
The pollen of another flower of the same plant may fall on the stigma. |
(b) Differences between Homogamy and Dichogamy:
|
Homogamy |
Dichogamy |
|
Anther and stigma of a bisexual flower mature at the same time. |
Anther and stigma of a bisexual flower mature at different times. |
(c) Differences between Protandry and Protogyny:
|
Protandry |
Protogyny |
|
Anthers of the flower mature earlier than the stigma. |
Stigma of the flower matures earlier than the anthers. |
(d) Differences between Entomophilous and Anemophilous flowers:
|
Entomophilous flower |
Anemophilous flower |
|
Pollination is carried out by insects |
Pollination is carried out by wind |
(e) Differences between advantages of Self and Cross-pollination:
|
Self-pollination |
Cross-pollination |
|
Parental characters are preserved |
New varieties are produced |
Solution D.2
(a) Long and feathery stigma: Help to trap pollen grains in wind-pollination
(b) Brightly coloured petals: Attracting insects for cross-pollination
(c) Smooth and light pollen: Easily carried by wind to enable cross-pollination
(d) Protruding and easily movable anthers: Even slightest wind can move them
(e) Fragrant nectar: Attracting insects for pollination
Solution D.3
Advantages of cross-pollination:
1. The offspring are healthier.
2. The seeds produced are abundant and viable.
3. New varieties may be produced by cross-pollinating two different varieties of the same species.
Disadvantages of cross-pollination:
1. Pollination is not always certain.
2. The pollen has to be produced in large quantity.
3. The process is uneconomical for the plant because the flowers have to be large, coloured, scented and have to produce nectar for attracting pollinating agents.
Solution D.4
The pollen tube grows out of the pollen grains by breaking through its exine. The pollen tube grows through the stigma and style by dissolving these tissues with the help of enzymes and reaches the ovary, where it enters the ovule through a minute pore called the micropyle.
Solution E.1
(a) The process is called pollination. Pollination is the process of transfer of pollen grains from the anther to the stigma.
(b) The given process is called cross-pollination.
(c) Cross-pollination occurs in plants such as Oxalis and Hibiscus.
(d) Advantage of cross-pollination:
• The offspring are healthier.
Disadvantage of cross-pollination:
• There is a lot of wastage of pollen as the pollen is produced in large quantities to ensure maximum pollination.
(e) Insect and birds participate in the process of cross-pollination.
Solution E.2
(a)
1 → Exine
2 → Intine
3 → Pollen tube
4 → Tube nucleus
5 → Generative nucleus
(b) Germination of the pollen grain takes place only after it falls on the stigma of the same plant species. The pollen grain is stimulated to germinate due to the secretion of sugars by the stigma.
(c) The function of part '4' (tube nucleus) is to direct the growth of the pollen tube towards the ovary.
(d) During germination of the pollen grain, part '5' (generative nucleus) present at the tip of the pollen tube divides into two sperm nuclei. The pollen tube enters one of the synergids and releases its two sperm nuclei. Of these, one sperm nucleus enters the egg cell and fuses with its nucleus, while the other sperm nucleus moves towards the two polar nuclei in the central cell and fuses with them.
Solution E.3
(a)
1 → Style
2 → Pollen tube
3 → Polar nuclei
4 → Embryo sac
5 → Antipodal cells
6 → Micropyle
(b) After fertilisation
(i) The ovary enlarges to form the fruit and the ovarian wall forms the fruit wall.
(ii) The ovule becomes the seed.
(c) Synergids help in nourishing the egg cell, guiding the pollen tube towards the egg, proper functioning of the pollen tube and release of sperm nuclei.
(d) Pollen grain is transferred to the stigma during pollination. Germination of pollen grain takes place only if it falls on the stigma. After germination, the pollen tube grows through the stigma and reaches the ovary for the fertilisation of the egg cell.