Natural disorders can cause extinction of species. Sudden, abrupt and group extinctions have occurred in nature due to
a) Over population of predators or competition from advanced descendents.
b) Genetic degeneration.
c) Changes in environment like excessive cooling or warming, drought or rains.
d) Natural calamities like floods, earthquakes, volcanoes, tsunamis, epidemics, etc.
Example : one theory of extinction of dinosaurs is the origin of giant crocodiles which devoured the dinosaurs and thereafter died down themselves due to absence of proper food.