List the reasons that account for the greater biological diversity in tropics.

Dear student,

Here are some reasons for why the tropical area has greater biological diversity - 

Almost constant environmental conditions which harbours the growth of various species.
Average annual temperature is greater then that of temperate areas.
Tropical areas receives much solar energy than that of temperate areas, having dense forest.
Dense forest supports the more complexity in the forest ecosystem, hence more the diversity.

Regards.