AST 248 Lecture 15: Lecture 15

• School: Stony Brook University
• Department: Astronomy
• Course: AST 248
• Professor: James Lattimer

Document Summary

Extinction was established as a fact by georges cuvier in 1796, and was critical for the spread of uniformitarianism in spite of the fact that cuvier viewed extinctions as evidence in favor of catastrophism and opposed lamarckian evolution theories. Over 99% of all species that have ever existed are now extinct. There have been 6 major and many minor (up to 20) extinctions observed in the fossil record. Nearly all divisions among geological eras, eons and periods are marked by extinctions and originations. A series of extinctions that eliminated many brachiopods and tribolites. A series of extinctions near the devonian-carboniferous transition, lasted 20 myr with several pulses. Ea(cid:396)th"s la(cid:396)gest e(cid:454)ti(cid:374)ctio(cid:374) killed 96% of all (cid:373)a(cid:396)i(cid:374)e species a(cid:374)d (cid:1011)(cid:1004)% of la(cid:374)d species (plants, insects, vertebrates). Ended dominance of mammal-like reptiles and led to dinosaur dominance. Cretaceous-tertiary extinction 65 myr about 50% of all species, including dinosaurs, were extinguished.