Campbel12.Chapter301

Adaptations of Seed Plants

  • Seed plants make up a vast majority of plant biodiversity due to several adaptations:

    • Reduced gametophytes:

      • Gametophytes develop in cones (gymnosperms) or flowers (angiosperms).

    • Heterospory:

      • Production of two types of spores (male and female).

    • Ovules and pollen:

      • Pollen allows for fertilization without water, as it can be dispersed by wind or animals.

  • Seed structure includes:

    • Embryo

    • Seed coat (protects the embryo)

    • Food supply (nourishes the embryo)

Life Cycle of Seed Plants

  • Sporophyte-dominated life cycles:

    • Gametophytes are microscopic and dependent on the sporophyte for nutrition.

    • Sporophyte is the dominant structure (2n).

Key Features of Seed Plants

  • Gametophyte Dependency:

    • Reduced gametophytes provide protection and nutrients from the parent plant.

  • Adaptation to Land:

    • Water is not required for fertilization, advantageous for survival in diverse habitats.

Overview of Gymnosperms and Angiosperms

  • Gymnosperms:

    • Bear protected "naked seeds" on cones.

    • Most common group: Conifers (pines, firs).

  • Angiosperms:

    • Reproductive structures include flowers and fruits, making them the most diverse group of plants.

Flower Structure and Function

  • Flowers consist of various organs:

    • Stamens (male reproductive) produce pollen.

    • Carpels (female reproductive) house ovules.

  • Pollination can occur through animals or wind.

Fruit Development

  • Fruits develop from the ovary and aid in seed dispersal.

  • Types of fruits include fleshy (e.g., tomatoes) and dry (e.g., nuts).

Seed Dispersal Mechanisms

  • Various adaptations ensure effective dispersal:

    • Parachute-like structures for wind dispersal.

    • Buoyant structures for water dispersal.

    • Burrs that cling to animals.

Importance of Seed Plants

  • Seed plants are critical for human welfare:

    • Major food sources, including crops like wheat and rice.

    • Provide raw materials like wood and medicines.

  • Preservation of plant diversity is essential due to habitat destruction and extinction risks.