The first question to ask is 'what exactly is a mass extinction'? A mass extinction (also known as an extinction event) is a time when levels of extinction are much higher than normal background levels for a large number of groups, and is not limited to one group or one environment. Mass extinctions are widespread: the have global affects, and they result in a large decrease in diversity and abundance in microscopic and macroscopic life.
No organism is immune to extinction, but there are characters that can help one survive a mass extinction. Organisms that are widespread are more likely to survive, as they are often more flexible and able to live in different environments. For example, if an animal is found only in a specific environment and a certain area of the world, and that area has a massive fire, then that animal will most likely die. Another thing that helps is numbers. If there are many of the animal, they are more likely to survive. For more details on what helps an animal survive a mass extinction, check out UK palaeontologist Dave Hone's post "How to survive mass extinction.
In the past, there have been several mass extinctions. In palaeontology, we refer to the "Big Five" mass extinctions. This week, we will talk about the first 3:
|Graph showing number of families of animals over time, indicating the 5 major mass extinctions. Image from UMass.|
|Diorama of typical Ordovician life before the extinction. Image from Wikimedia Commons|
|Typical Devonian ocean life. Image credit: University of Michigan University of Paleontology|
|Trilobite fossil from the Permian of Russia. Image from the Carnegie Institute for Science|
For more information, check out the BBC Nature website on mass extinctions!