BIOL360 Lecture Notes - Lecture 3: Stromatolite, Siberian Traps, Types Of Volcanic Eruptions
26 Mar 2018
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Document Summary
Extinctions and biodiversity loss: happen all the time because species have natural duration of existence (1000s to millions of years) Mass extinction times when 20-90% of a species is wiped out (5-6 times in history of earth) Extinction event smaller-scale extinctions; usually in certain regions or certain species. Background extinction normal or natural extinction (5-10% of species; happens approximately every 1 million years) Stepped pattern of decline: gradual or catastrophic change every m years. Common cause of extinction regular cause (astronomical, orbital changes, impact debris) every 26 m years: paleontologists disagreed with this. End of permian: 250mya; biggest extinction, pangaea was formed. Cretaceous-tertiary (k-t: 65mya, oceans filled gaps between continents, but oceans were 100-200m higher and 1/3 land submerged, meteorite killed plants, no food for reptiles went extinct; ammonites extinct, end of dinosaurs. Recovery is proportional to magnitude of event (10m years); p-t event took 100m years.
