GEOL 1020 Lecture Notes - Lecture 18: Milankovitch Cycles, Impact Crater, Lava Field
7 Dec 2017
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Mass extinction: temporal interval when extinction levels are significantly above those of adjacent intervals (i. e. large numbers of species go extinct) There are about 5 or 6 mass extinctions in the phanerozoic. A species disappears because it has evolved to the point of being called a new species. Local extinction a species (or genus, family, etc. ) disappears in the chosen area of study, but still exists elsewhere. Extinction total disappearance of a species or higher taxon. Groups of organisms that are well represented in the fossil record and have experienced high extinction rates (ex: mammal species). Over 80 hypotheses to explain dinosaur extinction, ranging from meteorite to alien hunting. Forams, particularly planktonic forms (floating in the water), suffered huge extinction. On land, vertebrate clades were among the greatest casualties of the k-pg extinction. Most of what we know comes from north america. The k-pg extinction was selective, affecting only certain groups such as dinosaurs, marsupial mammals, lizards, and sharks.
