Subject: Individuals average weight and species population

I'm interested in knowing about if there exists a relation between the 
average size of a living being and the abundance of its species (i.e. are 
there billions of ants as ants are rather small and only thousands of 
whales which are some bigger than ants?).

I would like to know about a database (or so) where all (or almost all) 
known species are listed with their average individual weight and 
population. I guess (and have heard of) there could exist a kind "power 
law" relation between size and population (population of a species 
inversely proportional to some power of the average weight of its 
individuals).

And, by the way, how many living species have been classified up to now?

Thanks in advance and congratulations for the pretty job you do.

Re: Individuals average weight and species population