The Earth has undergone constant change in its 4.54 billion year history with life evolving in response to those changes – in particular to the changing atmospheric compositions of carbon dioxide and oxygen. Species extinction has been a natural part of the evolutionary process of the planet however there are now thought to have been at least 8 mass extinction events in the history of the Earth – each of major consequence to life on the planet and of import to our modern understandings of climate change.
