GEOS 170A1 Lecture Notes - Lecture 19: Carbon Cycle, Chordate, Shortwave Radio
7 Aug 2018
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Document Summary
Gills, internal support, nerve cord: all life originates from the ocean. Mass extinctions - the rule not the exception: definition: events in which large numbers of species die, these are rapid events, by some estimate, for every species alive today, over 1000 have gone extinct! Mass extinctions - five mass extinction events in earth history: 430 ma - 60% of all species gone, 360 ma - 70% aquatic invertebrates gone, 250 ma - 80 - 95% marine species gone. 10 million years for reefs to reappear (reef gap): 204 ma - 1/2 marine invertebrates gone, and 80% of all land animals gone, 65 ma - all large land animals gone! Important extinction for us: biodiversity = number of various genera on the planet. The carbon cycle: carbon naturally moves between oceans, atmosphere, & lithosphere, humans are changing the cycle by returning carbon from fossil fuels to the atmosphere and oceans faster than it is removed from atmosphere.
