Question

what will happen if the earth were moving rotational motion only?

Answer 1

if that happens then we will not have Seasons Seasons will not occur

Answer 2

Answer:

If the earth were moving with rotational motion there would be the same season forever.  Hot areas might get even hotter and cold areas might get even colder.

There would be an imbalance in the nature and it may lead to  

a. Destruction of crops

b. Extinction of some animals

c. Melting of polar ice caps which may result in massive flood in coastal areas.