Answer the following question given this paragraph: 

The evolution of life on Earth wasn’t always smooth and steady—far from it. Living things had to cope with some astounding changes. Giant meteorites struck Earth’s surface. Continents drifted and shifted. Ice ages buried the planet in snow and ice for millions of years at a time. At least five times, many, if not most, of Earth’s living things went extinct. Extinction occurs when a species completely dies out and no members of the species remain. But life on Earth was persistent. Each time, it came back more numerous and diverse than before.


Q: Ice ages, continental drift, and giant meteorites striking earth have caused what phenomenon?


A:
extinction