Final answer:
The leading hypothesis for the Permian extinction includes massive volcanic activity causing global warming and anoxic conditions, with further speculations on asteroid impacts and climate changes due to glaciation and warming.
Step-by-step explanation:
The Permian extinction, occurring at the end of the Paleozoic Period, was the largest mass extinction on Earth, with drastic biodiversity losses both in the oceans and on land. Leading hypotheses for this cataclysmic event suggest that extended volcanic activity, which may have led to a runaway global-warming event, played a key role. This volcanic activity spewed enough basaltic lava, particularly in Siberia, to potentially induce severe warming, anoxic oceans, and a subsequent collapse of marine and terrestrial ecosystems.
Additionally, other speculations include asteroid impacts, similar to the one at the end of the Cretaceous period, and rapid climate changes caused by oscillations between glaciation and warming phases. These tumultuous conditions not only obliterated an estimated 96 percent of marine species and 70 percent of terrestrial species but also set the stage for the rise of new life forms in the Mesozoic Era, including the dinosaur's evolutionary lineage.