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Are there rules to mass extinctions? Mass extinction events have been identified

Are there rules to mass extinctions?
Mass extinction events have been identified periodically through the history of life, with five major extinctions occurring since the Cambrian period each of which eliminated over 20% of extant life, and with lesser mass extinctions being even more frequent. The point of this discussion is to consider, based on what we know about the causes of mass extinction, what the commonalities and differences are between each event. To begin, watch the TED Talk by Peter Ward on his research into the cause of the end-Permian extinction, the most severe event known. Then, look at Table 14.2 in the Zimmer & Emlen text. Choose one of the four remaining mass extinctions (besides the Permian) and dig a little deeper into what is known about it. For your first post, prepare a short paragraph identifying your extinction event, the prevalent theory as to its cause, and any plausible alternative explanations you found.
In your second post, initiate a discussion with a group member that posted on a different extinction. Together, compare and contrast key similarities and differences that are well-established between your event and theirs.
Prior to composing your third post, read the Ceballos et al. article. This study quantifies the rate of well-documented species loss due to human activities. In a third post, discuss ways in which the current extinction event resembles the Big 5, based on your readings, videos, and research. How does it differ? You might consider, for example, the different mechanisms by which species are lost, or which species are disproportionately affected. Finally, consider how the loss of biodiversity is likely to affect you, or your descendants.