Question

Mass extinctions occurred 250 million years ago and 65 million years ago. According to some scientists, which of the following reasons caused both mass extinctions? The Earth’s oceans changed a few degrees in temperature. The diversity in the gene pool decreased dramatically. A new species was introduced into an established ecosystem. A large comet or asteroid hit the Earth.

Answer 1

A large comet or asteroid hit the Earth

Answer 2

Depending on which scientists you are talking about the best answer for this question could be: A large comet or asteroid hit the Earth thereby causing mass extinction of organisms millions of years ago. Scientists are studying the possibility of this theory through carbon-dating bones or remains of organisms that they have dug from the ground.