Mass extinctions

Definition

Mass extinctions are events in which a significant percentage of all life forms on Earth become extinct in a relatively short geological period. These events drastically reduce biodiversity and can be triggered by natural disasters, climate changes, or human activities.

5 Must Know Facts For Your Next Test

1. There have been five major mass extinction events in Earth's history, the most well-known being the Cretaceous-Paleogene extinction that wiped out the dinosaurs.
2. The Permian-Triassic extinction event, also known as 'The Great Dying,' was the most severe, eliminating about 96% of marine species and 70% of terrestrial vertebrate species.
3. Mass extinctions can lead to adaptive radiations where surviving species diversify rapidly to fill ecological niches left vacant by extinct organisms.
4. Human activities, such as habitat destruction and pollution, are contributing to what many scientists consider the sixth mass extinction currently underway.
5. Fossil records provide critical evidence for studying past mass extinctions and understanding their causes and effects on global biodiversity.

Review Questions

• What are some of the primary causes that trigger mass extinctions?
• How do mass extinctions impact biodiversity and ecological niches?
• Why do scientists believe we may be experiencing a sixth mass extinction?

Related terms

Biodiversity: The variety of life forms within a given ecosystem, biome, or for the entire Earth.

Adaptive Radiation: The rapid evolution of diverse species from a common ancestor following an environmental change or mass extinction.

Fossil Record: The total number of fossils discovered and the information they provide about past life forms on Earth.