Write some examples of recent extinctions of species.

Give some examples of force of friction.

Name two recently extinct animal species.

Write two examples of carcinogens.

Write two examples of true fruits?

Write some examples of crustose lichens stage.

Write one example of periodic motion.

Write five examples of echinoderms.

List some causes of extinction of wildlife.

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