Unity is: all life requires DNA, all like requires a source of energy whether it be autotrophic or heterotrophic, all life must must be able to reproduce. all living things consist of one or more cells
Diversity: many many many different forms of DNA, many different types or organisms divided in kingdoms, phylums and so forth. the are mammals the are insects their are clams all with very different anatonomys. Their are different habits an organism can survive in, some organisms live in the ocean some on land, the list gots on and on
I hope that helps