Q. What is aquatic biodiversity?

Biodiversity found on Earth today is the result of 3.5 billion years of evolution. Until the emergence of humans, the Earth supported more biodiversity than in any other period in geological history. Since the advent of humans, however, biodiversity has begun a rapid decline, with one species after another suffering extinction. Estimates of global species diversity vary from 2 million to 100 million species, with a best estimate to somewhere near 12.5 million.

New species are regularly discovered (on an average about three new species of birds each year) and many, though discovered, are not yet classified (an estimate gives that about 40% of freshwater fishes from South America are not classified yet). Most of the diversity is found in tropical forests.