The 3 Main Criteria for determining if an organism is a plant: Multicellular (have many cells) Autotrophic (make their own food) Eukaryotic (have membrane bound organelles & nucleus) In addition, all plants have an alternation of generation life cycle (more on this later)

 Follow a similar path as Animals:  Microscopic Macroscopic  UnicellularMulticellular  SimpleComplex  WaterLand  DiffusionVascular System(transp/supprt)  No seedsSeeds

 The first plants appeared 600 mya - Proterozoic era  Probably arose from photosynthetic protists  Algae are still the most abundant/widespread plants  Algae provide 90% of earth’s biomass and oxygen  Green algae are the likely ancestors of land plants  First land plants arose during the Devonian-200mya  Gymnosperms arose in Pennsylvannian  Angiosperms arose in the Jurassic

 Algae: strictly aquatic;  Bryophytes (mosses and liverworts): first land plants; small and tied to water for reproduction  Ferns: 1 st land plants to have vascular tissue & thus can grow tall; tied to moisture for reproduction  Gymnosperms (conifers): have sophisticated vascular tissue; inhabits all habitats; seeds are naked  Angiosperms (flowering plants): same as G; seeds are enclosed & store food; great dispersal ability

A type of life cycle found in plants that alternates between 2 different versions of adult plants – the sporophyte and the gametophyte plant

 The lifecycle repeats, with sporophyte plants reproducing gametophyte plants and visa versa The Sporophyte plant produces spores, which after released, will germinate and each spore will grow into a new plant (the gametophyte)  The Gametophyte plant produces gametes, (eggs and sperm). After an egg and sperm unite (fertilization), the zygote will germinate and grow into a new plant (the sporophyte)

Sporophyte spores gametophyte gametes

Sporophytes & Gametophytes (attached)

Gametophytes Sporophytes rhizoids