Geologic Timeline Key Points
Key points along the geologic timeline. Data from Douglas Henderson Geologic Time Scale.Geologic Timeline Key Points I
| Timespan (memorize) | Key Points (memorize) |
|---|---|
| Archeozoic | (1) Earth's crust forms (2) 700 million year span of heavy asteroid and comet bombardment |
| Precambrian | (1) Archaean - single celled organisms (2) Proterozoic - earliest fossil animals & plants |
| Cambrian | (1) extinction of first great expansion of marine life (2) first animals with hard skeletons (mollusks, corals) (3) first chordates evolve (give rise to vertebrates) (4) first traces of vascular plants |
| Ordovician | (1) first land-based plants (2) second great expansion & diversity of marine life (jawless fish) |
| Silurian | (1) jawed fish (2) first land animals (arthropods) (3) widespread distribution of plants on land |
| Devonian | (1) amphibians appear (2) fish groups develop (3) insects appear (4) first forests (5) advanced plants evolve |
| Carboniferous | (1) mammal-like reptiles begin to dominate land (2) first reptiles develop & colonize land (3) amphibians evolve (4) trees dominate, club mosses, horsetails, ferns (5) gymnosperms (seed-bearing plants) first appear |
Geologic Timeline Key Points II
| Timespan (memorize) | Key Points (memorize) |
|---|---|
| Permian | (1) trilobites & other types of marine life disappear (2) mammal-like reptiles & archosaurs dominate land |
| Triassic | (1) primitive true mammals evolve (2) mammal-like reptiles disappear (3) dinosaurs appear (4) reptis diversify & dominate (5) gymnosperms evolve |
| Jurassic | (1) first birds evolve (2) dinosaurs reach gigantic forms (3) dinosaurs dominate animals (4) cycads, conifers |
| Cretaceous | (1) extinction of dinasaurs & marine reptiles angiosperms (flowering plants) evolve, modern plant type begins to appear (3) modern mammal begin to evolve (4) bird groups continue to evolve |
| Tertiary | (1) upright hominids appear (2) first apes appear (3) bird groups continue to evolve (4) mammal groups evolve & become dominant life on Earth |
| Pleistocene | (1) formation of agriculture & permanent communities (2) cro-magnon man, neanderthal man (3) ice age mammals, mammoths prominent |
| Quaternary | (1) growth of civilization (2) early civilization (3) modern man |
Memorize both together
Pages
♦ Geologic Timeline - geologic timeline with dates
♦ Geologic Timeline 2 - geologic timeline with key points
this section is inserted from the Geologic Timeline page
Pages
♦ Geologic Timeline - geologic time periods with dates
♦ Geologic Timeline 2 - geologic time periods with key points
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