The most diverse kingdom is likely Animalia.
Using the US (six kingdom) model, the order would be Bacteria Archaea Protista Fungi Plantae Animalia *(protists are arguably a diverse and polyphyletic group, which will likely be phased out in any new hierarchy of living things)
in the kingdoms
Rain Forest (: (Novanet)
There are more classes of organisms, since it is the most specific of the three.
Water is the most abundant compound in living organisms.
Structures and Features
Diverse organisms in a large region.
Where are you most likely to find the largest number of living organisms?
No. Most hydrocarbons are not found in living organisms.