bio 2/14

Seed and Generations

  • Sporophyte Generation

    • Zygotes formed through fertilization are diploid, signifying the sporophyte generation.

    • Sporophyte grows inside the seed, nourished by gametophyte tissue, which provides essential nutrients.

    • Example: Pine cones house seeds where each fertilized ovule develops into a seed.

Gymnosperms & Clades

  • Gymnosperms

    • Four major clades:

      • Ginkgo (single member)

    • The embryo present in seeds is diploid, marking it as part of the sporophyte generation.

    • Structure includes the seed coat, food supply from the mom (endosperm), and the embryo.

Plant Phylogeny

  • Seed Plants:

    • Both gymnosperms and angiosperms are seed plants.

    • Angiosperms (flowering plants) include flowers and fruits, differentiating them from gymnosperms.

Functions of Flowers

  • Role of Flowers

    • Specialized structures for reproduction that facilitate pollination.

    • Flowers create adaptations to promote relationships with pollinators (e.g., color, shape, scent).

    • Pollination mechanisms differ in gymnosperms (mainly wind) compared to flowers (which attract various pollinators).

Understanding Pollinators

  • Umwelt Concept:

    • Flowers exploit the unique sensory perceptions of animals.

    • Adaptation examples:

      • Different scents attract specific pollinators based on their senses.

      • Animals perceive colors and shapes distinctively.

Floral Structure

  • Components of a Flower

    • A flower is a modified stem with specialized leaves organized in whorls.

    • Whorls Description:

      • Outer: Sepals (protective structure for the bud)

      • Second: Stamens (male reproductive part, contains anther)

      • Third: Petals (attractive, often colorful part)

      • Innermost: Carpel (female part, houses ovules)

The Carpel's Role

  • Carpel Structure:

    • Contains stigma (pollen landing site), style (tube for pollen), and ovary (where ovules develop).

    • Additional structures:

      • Pistol: Older term for the carpel, not commonly used today.

Reproductive Processes

  • Double Fertilization:

    • Occurs when one sperm fertilizes the egg (forming diploid zygote) and another sperm fuses with polar nuclei (forming triploid endosperm).

    • Endosperm's Function:

      • Supplies nutrients to the developing embryo.

      • Important in human consumption (e.g., flour from wheat, which is endosperm tissue).

Life Cycle Phases

  • Seed Germination:

    • Seeds can remain dormant for extended periods until suitable conditions are present.

    • Upon germination:

      • Roots penetrate the soil, and shoots emerge towards the light, initiating plant development.

Summary of Key Terms

  • Complete Flower: A flower with all four modified structures (sepals, petals, stamens, carpel).

  • Incomplete Flower: A flower missing one or more structures (may still function for reproduction).

  • Sporophyte: Dominant generation in seed plants, responsible for structure and seed formation.

  • Gametophyte: Temporary structure primarily serving to produce the next sporophyte generation.