Which of the following is related with reproductive isolation

Given below some major events in the early history of life

$I.$ First heterotrophic prokaryotes

$II.$ First eukaryotes

$III.$ First autotrophic prokaryotes

$IV.$ First animals

Choose the correct sequence of these evolutionary events

For a long time it was believed that life came out of decaying and rotting matter like straw mud, etc.

This was the theory of

In nature, the occurrence of mutations are