Sexual Reproduction in Flowering Plants Ensures Genetic Diversity
- Flowering plants, or angiosperms, reproduce sexually to ensure genetic variation and adaptability.
- This complex process involves gamete production, pollination, fertilization, and embryo development, even in hermaphroditic plants that have both male and female reproductive organs.
Definition
Hermaphrodite
Any organism that can produce both male and female reproductive organs
Flowers Are Composed of Male And Female Reproductive Parts
Male Reproductive Parts (Stamen)
- Anther: Produces pollen grains containing male gametes.
- Filament: Supports the anther and positions it for effective pollination.
Female Reproductive Parts (Carpel/Pistil)
- Stigma: Receives pollen during pollination.
- Style: A tube connecting the stigma to the ovary.
- Ovary: Contains ovules where female gametes develop.
Gamete Production: Male and Female Contributions
Male Gametes Develop Pollen
- Inside the Anther:
- Diploid cells undergo meiosis, producing haploid cells.
- Each haploid cell develops into a pollen grain, which contains:
- Two male gametes (sperm cells).
- A tube nucleus to guide pollen tube growth.
A pollen grain acts like a delivery package, carrying male gametes securely through transport.
Female Gametes Develop The Ovule
- Inside the Ovary:
- Diploid cells undergo meiosis, producing haploid nuclei.
- One nucleus becomes the egg cell (female gamete), while others assist in fertilization or embryonic development.
The ovule is like a protective chamber, sheltering the egg cell until fertilization, similar to how a bird’s nest protects its egg.
Pollination: Transferring Pollen to the Stigma
Definition
Pollination
Pollination is the transfer of pollen from the anther to the stigma, a critical step preceding fertilization.
- There are two key methods of pollination:
- Wind Pollination: Grasses and conifers rely on lightweight pollen carried by the wind.
- Animal Pollination: Insects, birds, and mammals transfer pollen as they feed on nectar.
