PLANTS & THEIR EVOLUTION

The General Plant Life Cycle: Alternation of Generations Sporophytes are the diploid stage that grow by mitosis from a fertilized egg and produce spores Gametophyes are the haploid stage that develop from by meiosis from spores and produce gametes (egg and sperm)

Evolution in General As plants have become more adapted to land the sporophyte generation has become the dominant stage of the life cycle

Algae Simple filamentous non-vascular plants adapted to aquatic habitats

Moss (P. Bryophytes) 18,600 species Non-vascular gametophyte dominant plants that are adapted (limited) to moist habitats The sporophyte live off the gametophyte and requires water for sperm transport

Mosses Life Cycle

Fern (P. Pterophyta) >12,000 species Seedless vascular sporophyte dominant plants adapted (limited) to moist habitats Both generations can photosynthesize and water is required for sperm transport

Fern Life Cycle

Conifers or Cone Bearing Plants (Gymnosperms or P. Coniferophyta) >700 species Sporophyte dominant naked seed bearing (cones) vascular plants adapted to dry and cool habitats (needles) The gametophyte is reduced to a few cells in the spore that produce the sperm or eggs

Pollen The male spore/gametophyte is transported in pollen grains Pollen grains are transported by the wind

Conifer Life Cycle

Flowering Plants (Angiosperms or Anthophyta) >260,000 species Sporophtye dominant seed bearing (flowers) vascular plant adapted to most habitats The gameophyte as in conifers

Flowering Plant Life Cycle

Flowers & Fruit Many flowering plants have coevolved with pollinators to transfer their pollen Fruits are secondary flower structures that develop to promote seed dispersal