Evolution of Plants

Important events in Plant Evolution

1. Origin of Life
2. Origin of Land Plants
3. Origin of Seed habit
4. Origin of Flowering Plants

First "Plants" = Autotrophs

1. Cyanobacteria
2. Chrysophyta
3. Phaeophyta - Brown algae
4. Rhodophyta - Red algae
5. Chlorophyta - green algae
   • Receptaculids

Land Plants

Characteristics

1. Chlorophylls A and B
2. Accumulate starch
3. Oogamous - egg producing
4. Alternation of Generation

Factors to overcome - Water to Land

1. Salt water to Freshwater
2. Buoyancy and Support
3. Anchorage
4. Acquisition of water
5. Prevention of Desiccation
6. Reproduction

Evolution of Land Plants

1. . Chlorophytes
2. Bryophytes -
   • liverworts,
   • mosses
3. Psilophytes = Psilopsids (Late Silurian - Recent)
   1. Cooksonia - Silurian
   2. Zosterophyllum - Devonian
   3. Psilophyton - Devonian
4. Lycopsids - (Silurian - Recent)
   1. Lepidodendron
   2. Sigillaria
5. Sphenopsids (Devonian - Recent)
   1. Horsetail = scouring rush
   2. Calamites
   3. Annularia
6. Pteropsids (Devonian - Recent)
   • True Ferns
7. Progymnosperms (Devonian - Mississippian)
   • Homospores or
   • Heterospores
8. Gymnosperms = naked seed (Devonian? - Recent)
   1. Seed Ferns
      1. Neropteris
      2. Glossopteris
   2. Pinopsids = Conifers
      • Cordaites
   3. Ginkgoes (Permian - Recent)
   4. Cycads (Triassic - Recent)
9. Angiosperms = Flowering Plants (Lower Cretaceous - Recent)
   1. Monocots
   2. Dicots

Evolution of Leaves

1. Small, simple leaves
2. Larger, divided leaves

Evolution of Seeds

1. Gametophyte stage attached to Sporophyte stage.
2. Sex cells fertilized and encased in protective coat
3. Cones

Effects of Plants on the Land Surface

1. Chemical and Physical Weathering
2. Soils - organics
3. Weather and Climate
   • Transpiration
     1. 40 trees - 16 tons of H2O
     2. 100 gals/day/tree

History of Paleozoic Forests

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