KEY TAKEAWAYS •
Extinction is a natural part of the evolutionary process.
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Often extinctions don’t happen in isolation but involve disruptions in the food chain and competition changes in the environment that result in other extinctions.
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It is sometimes difficult to gauge extinction because it involves identifying species, which is also difficult to do.
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Background extinction rates vary throughout geological time but happen in the absence of a mass extinction event.
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There are multiple factors that contribute to mass extinction, which usually involves long-term pressures on the ecosystem and a short-term shock to the environment.
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There have been five major extinction events and numerous minor extinction events in geologic time.
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