What happen if there was no moon?

Answer 1

That depends if the Moon formed and then 'went' or if there never had been one...

As the oceans tides on Earth are caused by a combination of the Suns and Moons gravity then the Moon disappeared from orbit for some reason would obviously have an effect on this (and probably the Earths weather systems too). Exactly what this would mean though I'm not sure.

if Earth had never had a Moon then that would be quite different! A lot of current thinking is that the tides on the early Earth were mainly responsible for washing nutrients and the chemicals necessary for life from the land masses into the oceans. The Moon, when it was formed, was much closer to the Earth and so the tides were much bigger, often going far inland. Without these tides it is entirely possible that the chemicals for the 'primordial soup' (where the thinking is that life got started) might never have happened! So it's quite possible that No Moon = No Life!