Upper Block Cycles - Reproduction in Plants

Fundamental Principles of Reproduction

  • Purpose of Reproduction: Living things reproduce to ensure continuity of their own kind.

  • Inheritance of Traits: Many characteristics of organisms are passed on from parents to their offspring/young.

  • Cellular Basis of Inheritance: The nucleus in the cell contains genetic information responsible for transferring characteristics to offspring.

Processes of Sexual Reproduction in Flowering Plants

  • Four Main Stages: Sexual reproduction of flowering plants involves the following sequential processes:

  • Pollination: The transfer of pollen grains from the anther of one flower to the stigma of another, which is crucial for fertilization to occur. 1

    • Fertilisation (seed production)

    • Seed dispersal

    • Germination

Anatomy and Functions of Flower Structures

  • Anther: Produces pollen grains and stores them in pollen sacs.

  • Filament: Supports and holds the anther up.

  • Stigma: Receives pollen grains. The stigma is sticky and can trap pollen grains.

  • Style: Connects the stigma to the ovary.

  • Ovary: Protects the ovule and becomes the fruit after fertilisation has taken place. The fruit protects the seeds.

  • Ovule: Contains the female reproductive/sex cell and becomes the seed after fertilisation has taken place.

  • Petal: Attracts pollinators such as birds and insects to the flower.

Pollination Mechanisms and Agents

  • Definition of Pollination: Pollination involves the pollen grain (male sex cell) landing on the stigma of the flower. Specifically, pollination is the transfer of pollen grain from the anther to the stigma of the same flower or a different flower of the same kind.

  • Agents of Pollination (Pollinators):

    • Wind: Adapted with feathery stigmas and anthers that hang outside the petals to catch and release airborne pollen.

    • Insects: Adapted with colourful petals and nice scented-nectar to attract insect pollinators.

Fertilisation in Flowering Plants

  • Definition: Fertilisation is the process whereby the male reproductive cell fuses with the female reproductive cell.

  • Post-Fertilisation Changes: Fertilisation results in seed production within the flower, where the ovule becomes the seed and the surrounding ovary becomes the protective fruit.

Seed Dispersal Methods and Adaptations

  • Definition of Seed Dispersal: Seed Dispersal is the process whereby seeds are dispersed by wind, animals, water, or explosive action/splitting.

  • Characteristics and Structural Adaptations:

    • Wind Dispersal:

    • Wing-like structure: Helps the seed/fruit float in the air for a longer time.

    • Physical properties: Light and small, enabling them to grow in the direction of the wind.

    • Animal Dispersal:

    • External attachment: Hooks and stiff hair that catch onto animal fur or bodies.

    • Nutritional attraction: Juicy and fleshy fruits that entice animals to consume them.

    • Seed structural types (Hard / Indigestible Seeds):

      • Large seeds: Spat out by animals after eating the fruits.

      • Small indigestible seeds: Swallowed and passed out intact by animals in their droppings, allowing them to grow anywhere.