how many species of frogs is there? and are any dangerous, if so could they kill us?

Question: how many species of frogs is there? and are any dangerous, if so could they kill us?
- Keywords:
  animal,
  frog
Asked by c4bb4ge to Emma, Jimmy, Janet, Niall, Simon on 14 Mar 2013.
- Niall Crawford answered on 14 Mar 2013:
  
  So far, over 5000 species have been classified. But they hare finding new species all the time, especially in the rainforest.
  
  Some of the poison arrow tree frogs produce poisons strong enough to kill us, but these animals aren’t out to kills us, they only want to hunt small insects.

Question: how many species of frogs is there? and are any dangerous, if so could they kill us?