key term - Mass extinction

Definition

A mass extinction is a rapid and widespread decrease in the biodiversity on Earth, where a significant percentage of species die out in a relatively short period of geological time. Such events are often caused by catastrophic events or significant environmental changes.

5 Must Know Facts For Your Next Test

1. The Cretaceous-Paleogene (K-Pg) extinction event around 66 million years ago wiped out the dinosaurs and many other species.
2. Mass extinctions can be triggered by cosmic influences such as asteroid impacts, volcanic activity, and nearby supernovae.
3. The Permian-Triassic extinction event, occurring about 252 million years ago, is considered the most severe, eliminating approximately 96% of marine species.
4. Evidence of past mass extinctions can be found in the fossil record and through studying layers of sedimentary rock.
5. Mass extinctions have been pivotal in shaping Earth's evolutionary history by allowing new species to emerge and dominate.

Review Questions

Related terms

Biodiversity: The variety and variability of life forms within a given ecosystem, biome, or planet.

Asteroid Impact: A collision between an asteroid and a celestial body that can cause significant environmental changes.

Fossil Record: The totality of fossilized remains that provides evidence about the history of life on Earth.