Question

Write the main difference between self-pollination and cross-pollination.

Answer 1

Self-Pollination: The movement of pollen from an anther to the stigma of the same flower, or another flower on the same plant.
Cross-Pollination: The transfer of pollen from the anther of one flower to the stigma of a flower on a different plant of the same species.

Self-Pollination	Cross-Pollination
Pollination occurs within the same flower or between flowers on the same plant.	Pollination occurs between flowers on two different plants of the same species.
Does not require external agents such as wind, water, or insects for pollination.	Requires external agents such as wind, wa- ter, or insects for pollination.
Ensures genetic uniformity as no new genetic material is introduced.	Promotes genetic diversity as genetic material is exchanged between different plants.
Less adaptive to environmental changes due to a lack of variation.	More adaptive to environmental changes due to increased genetic variation.
Produces fewer seeds due to limited pollination opportunities.	Produces more seeds as cross- pollination increases fertilization chances.

Answer 2

Step 1: Insect Attraction Mechanism:
- Flower petals serve as the primary attractant for insects involved in pollination.
- Their vibrant colors and occasional fragrances are designed to entice insects like bees and butterflies.

Step 2: Pollination Process:
- Insect visits, prompted by petal attraction, result in contact with pollen.
- Insect movement between flowers facilitates pollen transfer from anthers to stigmas, achieving pollination.

Step 3: Post-Fertilization Changes:
- Completion of fertilization marks the end of the reproductive phase.
- With their attraction role fulfilled, petals typically senesce and detach.
- Plant resources are then redirected towards seed and fruit development.

Step 4: Summary:

Petals are the floral component responsible for attracting insects for pollination, often employing bright colors and scents.
Following fertilization, these petals generally wither and detach.

Answer 3

Step 1: Fertilisation Defined:
- Fertilisation is the union of the male gamete (pollen) and the female gamete (ovum) to create a zygote.
- This fusion takes place within the flower's ovary, specifically inside the ovule.

Step 2: Fertilisation Process in Flowers:
1. Pollen from the anther lands on the stigma.
2. A pollen tube grows from the pollen, travels down the style, and reaches the ovary.
3. The male gamete moves through the pollen tube and merges with the female gamete in the ovule.
4. This fusion results in the zygote.

Step 3: Post-Fertilisation Ovule Development:
- Ovules develop into seeds.
- Each fertilised ovule contains a zygote that grows into an embryo, protected by a casing to form a seed.

Step 4: Post-Fertilisation Ovary Development:
- The ovary develops into the fruit.
- The ovary wall becomes the fruit wall (pericarp), enclosing the seeds.

Step 5: Summary:

Fertilisation: The male gamete (pollen) fuses with the female gamete (ovum) to form a zygote.

Post-Fertilisation Outcomes:
Ovules: Transform into seeds.
Ovary: Develops into the fruit.

Answer 4

Seed Anatomy:
A seed contains an embryo destined to become a new plant. The embryo comprises:
- Plumule
- Radicle
- Cotyledon

Shoot Development:
- The plumule develops into the plant's shoot system (stem and leaves).
- It emerges upwards during germination to form the future shoot.

Root Development:
- The radicle develops into the plant's root system.
- It is the initial part of the seedling to emerge during germination, growing downwards into the soil.

Cotyledon Function:
- The cotyledon serves as a food reserve within the seed.
- It nourishes the embryo during germination until the seedling can photosynthesize.

Summary:
- Plumule → Future shoot
- Radicle → Future root
- Cotyledon → Embryo nourishment during germination