How Many Mass Extinctions Have There Been?

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Want to learn more about the topic in this week’s video? Here are some keywords/phrases to get your googling started:
– Mass Extinction Event: a significant, global decrease in the diversity of life
– "Big 5": The five biggest mass extinction events since the Cambrian explosion of Life 550 million years ago
– Biodiversity Crisis: Like a mass extinction, a biodiversity crisis is a marked depletion in diversity in the fossil record. Some scientists prefer to call the late-Devonian extinction a "biodiversity crisis" because a lack of speciation contributed to the loss in diversity just as much as extinction did.
– Diversity curve: A line chart that shows the diversity of life (usually by genera, but sometimes by species or family) over time
– Lagerstatte: a deposit of sedimentary rock that contains a profound number of fossils, often with excellent preservation
– Shareholder Quorum Subsampling: A statistical method that corrects for some of the biases in the fossil record, allowing scientists to generate more accurate diversity curves
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Credits:
Script Writer: Emily Elert (twitter:@eelert)
Script Editor: Kate Yoshida (twitter:@KateYoshida)
Video Illustrator: Ever Salazar (twitter:@eversalazar)
Video Director: Emily Elert (twitter:@eelert)
With Contributions From: Henry Reich (twitter:@minutephysics), Alex Reich (twitter:@alexhreich), Peter Reich
Music by: Nathaniel Schroeder: http://www.soundcloud.com/drschroeder
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References:

Alroy, J. (2015). Personal Communication.

Alroy, J. (2008). Dynamics of origination and extinction in the marine fossil record. Proceedings of the National Academy of Sciences, 11536-11542. Retrieved April 8, 2015, from http://www.ncbi.nlm.nih.gov/pmc/artic...

Alroy, J. (n.d.). Accurate and precise estimates of origination and extinction rates. Paleobiology, 40(3), 374-397. Retrieved September 20, 2015, from https://www.nceas.ucsb.edu/~alroy/pdf...

Benton, M. (2003). When life nearly died: The greatest mass extinction of all time. New York: Thames & Hudson.

Barrett, Paul M. (2015). Personal Communication.

Fossilworks: Gateway to the Paleobiology Database.
http://fossilworks.org/?page=paleodb

Lloyd, GT, Smith, AB and Young, JR, (2011). Quantifying the deep-sea rock and fossil record bias using coccolithophores. Geological Society Special Publication, 358 (1), 167-177.

Mcghee, G., Clapham, M., Sheehan, P., Bottjer, D., & Droser, M. (2013). A new ecological-severity ranking of major Phanerozoic biodiversity crises. Palaeogeography, Palaeoclimatology, Palaeoecology, 370, 260-270.

Raup, D. (1979). Biases in the fossil record of species and genera. Bulletin of the Carnegie Museum of Natural History 13: 85–91.

Raup, D., & Sepkoski, J. (1982). Mass Extinctions in the Marine Fossil Record. Science, 215(4539), 1501-1503.

Vermeij, GJ. (2015). Personal Communication.