GSCI 1052 Lecture Notes - Lecture 14: Osteichthyes, Igneous Rock, Paleozoic
23 Jan 2018
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Lecture 14: extinctions and the rise of the dinosaurs. Extinction: the death of the last individual of a species: species approach extinction when birth rates drop lower than death rates. Types of extinction: background extinctions- extinctions of individual species. They occur all the time due to a wide variety of causes: mass extinction: the extinction of many species in a geologically short time. The extinctions are the result of one or a few causes. Factors affecting background extinctions: competition from other (often invasive) species, depletion of resources, climate change, change in geography (ex. Weathering of mountains: volcanic eruptions, drying of aquatic habitats, flooding of terrestrial habitats, recently, humans have played a major role. Five major mass extinctions: late ordovician, late devonian, permo-triassic, triassic-jurassic, and cretaceous-tertiary (ends age of dinosaurs). Late ordovician: an extinction at the end of the cambrian was followed by a pulse of rapid evolution in the. Ordovician: tiering became common as crinoids grew to different heights.
