The scientist believe that evolution is gradual. But extinction, part of evolutinary story, are ' sudden ' and 'abrupt' and also group-specific. Comment whether a natural disaster can be the cause for extinction of species.

Explanation

Yes, a natural disaster can be the cause for extinction of species. As new sepecies evolve to fit ever changing ecological niches, older species fade away. But, the rate of extinction is far from constant.
In last 500 million years, 50-90% or more of all species on earth have disappeared in a geological blink of the eye. Many times, these mass extinctions had been the consequence of a natural disaster.
The most studied mass extinction between the Cretaceous and Palaeocene periods about 65 million year ago, killed off the dinosaurs and made room for mammals to rapidly diversify and evolve. The cause is suspected to be volcanic eruption and impact of large asteroids or comets striking the earth.