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
  • \