Re: How many types frogs are in the whole world?

There are approximately 4,000 species of frogs and toads, with more species 
being discovered each year. 
(http://www.rainforest-alliance.org/kids&teachers/kids/frog-pond/)

The United States has about 90 species. http://www.frogweb.gov/


 Unfortunately, many species are dying out,due to pollution and habitat 
destruction.  Frogs, like all amphibians, have a porous skin.  This means 
that water can "leak" out of their skin, and pollutants can "leak" in.  
Because of this, amphibians are very sensitive to climate changes and any 
toxins in their environments.  Scientists use frogs and toads to tell the 
health of a particular environment: if the frogs are healthy, then the 
habitat probably is, too!

Sincerely,
S. Kohler
Your mad scientist