Extinction events are significant occurrences in Earth's history when a large number of species die out in a relatively short period. These events can be caused by various factors, including drastic climate changes, volcanic eruptions, or asteroid impacts. One of the most famous extinction events is the Cretaceous-Paleogene extinction, which led to the demise of the dinosaurs around 66 million years ago. There have been five major extinction events, often referred to as the "Big Five." Each of these events drastically altered the course of evolution and the diversity of life on Earth. Understanding these events helps scientists learn about the resilience of ecosystems and the potential impacts of current environmental changes.