Patterns in frequency Extinction event

phanerozoic biodiversity shown fossil record

mass extinctions thought result when long-term stress compounded short term shock. on course of phanerozoic, individual taxa appear less become extinct @ time, may reflect more robust food webs less extinction-prone species , other factors such continental distribution. however, after accounting sampling bias, there appear gradual decrease in extinction , origination rates during phanerozoic. may represent fact groups higher turnover rates more become extinct chance; or may artefact of taxonomy: families tend become more speciose, therefore less prone extinction, on time; , larger taxonomic groups (by definition) appear earlier in geological time.

it has been suggested oceans have gradually become more hospitable life on last 500 million years, , less vulnerable mass extinctions, susceptibility extinction @ taxonomic level not appear make mass extinctions more or less probable.

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