Sexual Reproduction in Flowering Plants

Definition: Sexual reproduction involves the fusion of male and female gametes, leading to the formation of seeds.
Key Structures:
- Flower: The reproductive structure, typically consisting of petals, sepals, stamens, and carpels.
- Stamen: Male reproductive organ, made up of:
  - Anther: Produces pollen (male gametes).
  - Filament: Supports the anther.
- Carpel (Pistil): Female reproductive organ, made up of:
  - Stigma: Receives pollen.
  - Style: Connects stigma to ovary.
  - Ovary: Contains ovules (female gametes).
Pollination:
- Transfer of pollen from anther to stigma.
- Types:
  - Self-pollination: Pollen fertilizes the same flower (or another flower on the same plant).
  - Cross-pollination: Pollen from one plant fertilizes another; often involves agents like wind, insects, or animals.
Fertilization:
- Occurs when pollen reaches the ovule, leading to the formation of a zygote.
- Involves sperm cells traveling through the pollen tube to the ovule.
Development of Seeds:
- After fertilization, the fertilized ovule develops into a seed.
- The ovary develops into a fruit, which protects the seeds and aids in their dispersal.
Diversity in Flowering Plants:
- Over 250,000 species exhibit varying methods and structures for reproduction.
- Factors like flower shape, color, and scent can attract different pollinators, enhancing genetic diversity.
Importance of Sexual Reproduction:
- Promotes genetic variation.
- Increases adaptability to changing environments.
- Essential for the continuation of species.
Examples:
- Daisy: Composite flower structure with diverse pollination strategies.
- Orchids: Highly specialized flowers evolved to attract specific pollinators.

Sexual Reproduction in Flowering Plants

Sexual reproduction involves the fusion of male and female gametes, resulting in seed formation.
The key structures in sexual reproduction are the flower, stamen, and carpel.
The stamen is the male reproductive organ, composed of the anther, which produces pollen, and the filament, which supports the anther.
The carpel, or pistil, is the female reproductive organ, comprised of the stigma, which receives pollen; the style, which connects the stigma to the ovary; and the ovary, which contains ovules (female gametes).
Pollination is the transfer of pollen from the anther to the stigma.
There are two types of pollination: self-pollination and cross-pollination.
- Self-pollination occurs when pollen fertilizes the same flower or another flower on the same plant.
- Cross-pollination involves pollen from one plant fertilizing another plant; this often involves agents like wind, insects, or animals.
Fertilization happens when pollen reaches the ovule, leading to the formation of a zygote.
- This involves sperm cells traveling through the pollen tube to the ovule.
Seeds develop after fertilization, with the fertilized ovule becoming a seed.
- The ovary develops into a fruit, which protects the seeds and aids in their dispersal.
There are over 250,000 species of flowering plants with varying methods and structures for reproduction.
- Factors like flower shape, colour, and scent can attract different pollinators, enhancing genetic diversity.
Sexual reproduction promotes genetic variation, increasing adaptability to changing environments.
It is essential for the continuation of plant species.
Examples of flowering plants with diverse pollination strategies include daisies, with their composite flower structure, and orchids, which have highly specialized flowers evolved to attract specific pollinators.

Sexual Reproduction in Flowering Plants

Sexual reproduction: Involves fusion of male and female gametes forming seeds and the next generation of plants.

Key Structures

Flowers: are the reproductive structures of flowering plants (angiosperms).
Stamens: Male reproductive parts, comprising anthers and filaments.
Anthers: Produce pollen, which contains male gametes.
Pistils: Female reproductive parts, consisting of stigma, style, and ovary.
Ovary: Contains ovules, which house female gametes.
Stigma: Receives the pollen during fertilization.

Pollination

Transfer of pollen from anthers to stigmas.
Self-pollination: Pollen fertilizes the ovules of the same flower or plant.
Cross-pollination: Pollen is transferred from one flower to another, leading to increased genetic diversity.
Mechanisms: Wind, animals (including insects and birds), water, and artificial means facilitate pollen transfer.

Fertilization

Fusion of a male gamete from pollen with a female gamete from the ovule.
Results in a zygote that develops into a seed.

Seed Development

Occurs within the ovary post-fertilization.
Seed composition:
- Embryo: Develops into the new plant.
- Endosperm: Provides nourishment to the embryo.
- Seed coat: Protects the seed.

Fruit Formation

After fertilization, the ovary develops into a fruit, aiding in seed dispersal.
Fruit types:
- Fleshy fruits: Attract animals for consumption, facilitating seed dispersal.
- Dry fruits: Release seeds upon maturity.

Advantages of Sexual Reproduction

Enhances genetic variation, promoting adaptation and resilience in plants.
Drives evolution and species formation through gene recombination.

Life Cycle

Alternates between two generations:
- Diploid generation: Sporophyte uses meiosis to produce spores.
- Haploid generation: Gametophytes use mitosis to produce gametes.