Selina Concise Solutions for ICSE Class 9 Biology Chapter 5 Pollination And Fertilization

Exercise 1

Question A:
Answer: 1. (c) Stigma and anthers mature at the same time
2. (b) Pollen grain
These conditions ensure that self-pollination happens effectively within a single flower because both parts are ready at once. The pollen grain is the tiny structure that carries the male reproductive cells to the female part of the flower.
Teacher's Tip: Remember "Same time, Same flower" for successful self-pollination.
Exam Tip: Write both the option letter and the full text of the answer for objective questions to avoid confusion.

Question B.1:
Answer: (a) Generative nucleus - (i) Male nuclei
(b) Germ pore - (ii) Pollen tube
(c) Exine - (iii) Rough
(d) Secondary nucleus - (iv) Endosperm nucleus
(e) Integument - (v) Testa
(f) Egg nucleus - (vi) Fertilization
Each part of the pollen and the ovule has a specific role in the complex process of creating a seed. For example, the exine is the tough, protective outer layer that keeps the pollen safe during its journey.
Teacher's Tip: Think of "Exine" as the "External" coat of the pollen grain.
Exam Tip: When matching columns, write the correct pairs side-by-side instead of drawing criss-cross lines.

Question B.2:
Answer: (a) butterflies
(b) wind
(c) water
Pollination can happen through different agents like insects, air, or water depending on the flower's structure. Flowers usually adapt their shape and smell to attract the specific agent they need.
Teacher's Tip: Think of butterflies as "Nature's delivery pilots" for pollen.
Exam Tip: Use specific examples of agents like "Honey bees" or "Wind" to show you understand how pollination works.

Question B.3:
Answer: (a) autogamy
(b) dichogamy
(c) Vallisneria
These scientific terms describe the different ways plants manage the timing and method of pollination. $Vallisneria$ is a classic example of a plant that uses water to move its pollen.
Teacher's Tip: "Auto" means self, so "Autogamy" is self-marriage or self-pollination.
Exam Tip: Learn the scientific names of plants like $Vallisneria$ as they are often used in "Identify the following" questions.

Question B.4:
Answer: (a) Ovules
(b) Ovary
(c) Ovarian wall
After fertilization, the different parts of the flower transform into the various parts of the fruit we eat. The ovules become the seeds, while the ovary itself grows into the fleshy part of the fruit.
Teacher's Tip: Remember: Ovule = Seed, Ovary = Fruit.
Exam Tip: Be very careful not to mix up "Ovule" and "Ovary" when describing post-fertilization changes.

Question B.5:
Answer: (a) Bisexual flower
(b) Inflorescence
(c) Self-pollination/Autogamy
(d) Dichogamy
(e) Heterostyly
(f) Entomophily
(g) Ornithophily
These terms are used to classify flowers and the specific ways they interact with pollinators. For instance, "Ornithophily" refers specifically to flowers that are pollinated by birds.
Teacher's Tip: "Entomo" always refers to insects, just like in "Entomology."
Exam Tip: Memorize these technical terms as they are perfect for scoring full marks in one-word answer sections.

Question C.1:
Answer: (a) Ornithophily-Pollination affected by birds
(b) Elephophily-Pollination affected by elephants
(c) Artificial pollination-Pollination affected by man through artificial means
Pollination isn't just for bees; even huge animals like elephants can help spread pollen in certain tropical plants. Humans also use artificial pollination in farming to create better crop varieties.
Teacher's Tip: Think of "Ornitho" as related to "Ornithology," the study of birds.
Exam Tip: When defining these terms, always mention the "agent" responsible for the transfer of pollen.

Question C.2:
Answer: (a) Ovules-Seed
(b) Calyx-Falls off or remains intact in dried and shrivelled form
(c) Petals-Fall off
(d) Stamens-Fall off
Once fertilization is complete, the flower's "job" of attracting pollinators is over, so the bright petals and stamens are no longer needed. The plant then focuses all its energy on developing the seed from the ovule.
Teacher's Tip: Think of the petals like "party decorations" that get taken down once the party (pollination) is over.
Exam Tip: Mentioning that the calyx sometimes "remains intact" (like on a tomato) earns you extra points for detail.

Question C.3:
Answer: Contrivances in flowers which favour cross-pollination:
1. Unisexuality
2. Different timings of maturation of androecium and gynoecium
3. Self-sterility
4. Structural barriers
Plants have clever ways to make sure they don't pollinate themselves, which helps them create stronger offspring. By ripening their male and female parts at different times, they ensure they must trade pollen with a neighbor.
Teacher's Tip: Contrivances are just "tricks" or "arrangements" the flower uses to reach its goal.
Exam Tip: Use a numbered list to present these points clearly for the examiner.

Question D.1:
Answer: (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
Every structural feature of a flower is designed to help it survive and reproduce in its specific environment. For example, wind-pollinated flowers have feathery stigmas that act like nets to catch pollen floating in the air.
Teacher's Tip: Think of the feathery stigma as a "pollen net" catching dust in the breeze.
Exam Tip: Match the structure (e.g., feathery stigma) with the agent (e.g., wind) for a complete explanation.

Question D.2:
Answer: 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.
Cross-pollination leads to stronger, more diverse plants, but it is a risky and "expensive" process for the plant. It requires a lot of energy to grow big, bright, smelly flowers just to get an insect's attention.
Teacher's Tip: Cross-pollination is like "variety is the spice of life" for the plant kingdom.
Exam Tip: Always list both advantages and disadvantages in separate sections to show a balanced understanding.

Question E.1:
Answer: 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.
The pollen tube acts like a guided tunnel that helps the male nuclei reach the egg inside the ovule. This journey requires the plant to use special enzymes to carve a path through the flower's solid tissue.
Teacher's Tip: Think of the pollen tube as a "drill" that creates a path for the male cells.
Exam Tip: Mention the "micropyle" as the specific entry point to show high scientific accuracy.

Question E.2:
Answer: 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.
The stigma provides a sugary liquid that acts like a "fuel" to start the growth of the pollen grain. The generative nucleus is the most important part because it contains the genetic information needed to create a new plant.
Teacher's Tip: The tube nucleus is like the "GPS" that leads the way, while the generative nucleus carries the "cargo."
Exam Tip: Be sure to explain the division of the generative nucleus into "two sperm nuclei" for full marks on fertilization questions.

Question E.3:
Answer: (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.
This detailed look at the inside of the ovary shows the final destination for the pollen tube. The synergids act as "guides" to make sure the sperm nuclei arrive safely at the right spot.
Teacher's Tip: Think of the embryo sac as the "nursery" where the new plant begins its life.
Exam Tip: When describing the transformation of parts, use the specific term "fruit wall" for the ovarian wall.