Final answer:
The End-Permian Mass Extinction event, the largest in Earth's history, took place at the end of the Permian Period and resulted in the loss of about 96% of marine species and 70% of terrestrial species, with major changes in the environment suggested as the leading causes.
Step-by-step explanation:
The End-Permian Mass Extinction occurred at the conclusion of the Permian Period, approximately 290 to 245 million years ago. During this event, Earth's diversity was severely diminished, with estimates indicating that around 96 percent of all marine species and 70 percent of terrestrial species were lost. Notable is the extinction of the trilobites, which were among the organisms that did not survive this mass extinction.
The causes of the End-Permian Mass Extinction are not entirely clear, but the main hypotheses point to a cataclysmic change in the environment due to massive, extended volcanic activity leading to global warming. This warming might have caused a significant reduction in oxygen levels in the oceans, creating anoxic conditions deadly to marine life. In addition, the formation of the supercontinent Pangaea reduced shallow coastal habitats, impacting marine diversity. The recovery from the mass extinction event was slow, taking up to 30 million years for terrestrial tetrapod diversity to rebound and significantly altering the course of evolution.