Extinction is the total cessation of a species or higher taxon level, reducing biodiversity
- It can result gradually, as one population of organisms progressively evolve into something else (phyletic extinction)
- Alternatively, a species may not leave any identifiable descendents and simply cease to exist (abrupt extinction)
Extinction can be caused by a range of factors, including habitat degradation, predation, disease or natural disaster
- Over 99% of species that have ever existed on Earth are now extinct
Mass extinction events are categorised by an unusually high number of species dying out in a relatively short period
- There have been five commonly recognised mass extinction events in the history of the Earth
Mass Extinction Events
1. Ordovician–Silurian mass extinction (~450 million years ago): Approximately 60 – 70% of all species wiped out
2. Late Devonian mass extinction (~370 million years ago): Over 75% of all species wiped out
3. Permian mass extinction (~250 million years ago): Roughly 96% of all species were wiped out
4. Triassic mass extinction (~200 million years ago): Over 50% of all species were wiped out
5. Cretaceous mass extinction (~65 million years ago): Approximately 80% of all species wiped out
Timeline of Mass Extinction Events
