Extinction is the rule, and survival the exception. 99.5% of species that have ever existed on Earth are now extinct. Extinction is a combination of bad genes and bad luck.

Types of extinction

Pseudoextinction, or phyletic extinction - One species evolves into another and there is no loss of species. An example of this would be the missing link between humans and apes.
True extinction, or terminal extinction - A species lineage becomes extinct, resulting in a loss of species.

Modes of extinction

Field of Bullets
Field of Bullets is one possible extinction scenario, where the removal of an organism is caused by an accident that has no connection to a species' adaptability or adjustment to its environment, or the fitness of individuals. It is a random and purposeless process, like standing in a field of bullets.

All species are effected by the same probability of extinction, regardless of classification, habitat, size of population, etc. This is the type of extinction expected after a large meteorite strike, which is one theory for the mass extinction of the dinosaurs 65 million years ago.

A Field of Bullets extinction opens up scope for new life to flourish, as demonstrated by the rise of mammals after the death of the dinosaurs.

Fair game extinction
This is Darwins's survival of the fittest. Extinction occurs as a response to the normal conditions a species may face, and that species' ability to adapt to those conditions.

Wanton extinction
Wanton extinction selects species for extinction through some method other than natural selection, which is based on the fitness of the species. For instance, geological events may wipe out all of the living members of a species because their habitat was located at the point of that event.