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