Seeded plants(class)

• all plants share:   * autotrophs   * cell walls
• all land plants:   * multicellular embryos   * alteration of generations   * apical meristems   * multicellular gametangia
• ferns onwards:   * vascular system   * sporophyte dominant
• gymnosperm + angiosperms   * dependent embryo   * seeds     * multicellular     * protected by seed coat     * can remain dormant for long time till conditions are right     * can be dispersed away from parents via wind, water, animals     * contain own food supply
• Charophytes = basal taxon
• Key adaptations:   * reduced gametophyte stage (within the seed)     * better for reproduction (protected from environment, gain nutrient from parent)   * heterospory     * two types of spores (megaspore → female gametophyte; microspore → male gametophyte)     * adds extra structures (megasporangia, microsporangia)     * beneficial for genetic variation, in case of inbreeding   * ovules (mature into seeds)     * integument → megasporangium → meiosis → megaspore(n)→ female gametophyte (n) → archegonium (n) → egg(n)     * integument→ seed coat; female gametophyte → food supply; egg (+sperm) → zygote (2n)     * integument: diploid structure protecting seed   * pollen     * microsporangium (2n), microsporocyte (2n) →meiosis → microspore (n) → mature pollen grain (n) → pollination → growth of pollen tube → discharge of nonmobile sperm into female → fertilization → zygote → embryo
• sporophyte → sporophyll →sporangia
• Gymnosperms
• most are conifers
• “naked-seed” plants
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