What are the five major Mass Extinctions known as the Big Five?

The Big Five Mass Extinctions are the End-Ordovician, Late Devonian, Permian-Triassic, Triassic-Jurassic, and Cretaceous-Paleogene events, each wiping out a large percentage of Earth's species.

Which Mass Extinction was the most severe in Earth's history?

The Permian-Triassic extinction, also called the Great Dying, was the most severe, eliminating about 96% of marine species and 70% of terrestrial vertebrates.

How do past Mass Extinctions inform our understanding of the current biodiversity crisis?

Past Mass Extinctions show how rapid climate change, volcanism, and oceanic anoxia can drive massive species loss; today's human-induced changes mirror these triggers, warning of a potential sixth Mass Extinction.