Question

which was a main force driving extensive speciation when the environment became hospitable to life after the

increase in interbreeding between organisms of different species

increase in genetic diversity among surviving organisms

increase in available ecological niches

increase of atmospheric oxygen to present levels

Explanation:

• Interbreeding between different species would not drive speciation (it would rather mix gene pools).
• An increase in genetic diversity among surviving organisms can lead to more variation, which is a raw material for speciation as different genetic variants may adapt to different niches.
• An increase in available ecological niches provides opportunities for organisms to adapt to different environments, driving speciation as different populations adapt to different niches.
• The increase of atmospheric oxygen to present - levels is more of a general environmental change that may support life but is not as directly a main force for extensive speciation as the availability of ecological niches.

Answer:

increase in available ecological niches