Lecture 2: Evolution Of Plants Flashcards
Geological time scale
- Present
- Holocene: the current warm period. 11, 700 yr to present.
- Quaternary: ice ages
- Hominids
- Extinction of the dinosaurs: 65 Ma
- Flowering Plants: 145 Ma
- Early Mammals: 208Ma
- Gymnosperms (seed-producing plants) and amphibians: 362Ma
- Land Plants: 420 Ma
Origin of plants
Precambrian (Earliest forms of plant life)
900 million years ago = ‘Supercontinent’
Algae
Cambrian and Ordovician periods (540 - 440 Ma)
Silurian period (440-410 Ma)
1st land plants
Soil begin develop
Plants move out of water onto land
Cooksonia
Extinct group of primitive land plants
Plant adaptations to survive on land
- surface to prevent drying out (cuticle)
- pores for gas exchange & regulate H2O loss (stomata)
- vascular system to distribute H2O, minerals & food (xylem & phloem)
- support to give structure to plant body (vascular tissue, lignin). Grow taller to reach light
- an anchoring system (roots)
……..
The first forests
- 395-286 Ma. Devonian and Carboniferous
- terrestrial fauna evolved from one composed of small vascular & non-vascular plants to a vegetation that included trees towering…..
Lepidodendron ‘scale tree’
- extinct genus of primitive tree related to the club mosses (not a moss)
Lepidodendron ‘scale tree’
Calamites: extinct genus of arborescent (trees) horsetails
Coal formation
350-300 Ma - Carboniferous Swamp Forests
% of CO2 & O2
CO2 removed by plant growth and limestone rock formation in Carboniferous
Evolution of Gymnosperms (seed-producing plants)
- originated in early Carboniferous …
Gymnosperms
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Extant Gymnosperms
- Conifers
- Cycads
- Ginkgo biloba (maidenhair tree)
- Gnetales: Ephedra (arid areas), Gnetum (tropical evergreens), Welwitschia mirabilis
.
Evolution of the Angiosperms
(Flowering Plants)
- 1st flowering plants appeared in the fossil record from ~140Ma (Cretaceous Peirod)
Angiosperms
Evolution of grasses: Eocene Epoch (Tertiary) (65 - 50 Ma)
- appearance of grasses mark one of most important evolutionary events for humankind.
- presently, there more than 10,000 species of grasses on the planet
- ## grass-dominated ecosystems (tropical & subtropical savannah, temperate grasslands, and steppes) cover more than 30% of earths land surface
Changing earth
Plate tectonics: why plant evolution related to periods of increased continental plate movement?
- amount of available land area (as compared to around of ocean)
….