Why is ocean climate (and the entire earth for that matter) divided into latitude parallel zones that become progressively colder from equator to pole?

Can someone me? i need to have this done as soon as possible! i'm putting 20 points on this!

Acivilization exists for several hundred yeaars, developing its own language. such a civilization probably has been: a. farming corn b. suffering from a lack of contact with the outside world. c. isolated by mountains or some other physical barriers. d. starving from lack of trade.

After world war 2, many people moved from the cities to?