What would happen to an organism is
mitosis did not occur

If there is no mitosis, there would be no cell growth and cell reproduction. Most importantly, genetic information cannot be passed on. All cell functions would be hugely affected.

It might. it might because if you think about if they discovered if we came from (lets say something funny like aliens) and thy found cells that matched and they would have t do more research about it but would most probably change their theory.