In what countries is it possible to enter a life science PhD program directly after a Bachelor's? I would like to know which countries allow admission to a PhD program directly after finishing a Bachelor's (Life Science), without requiring an intervening Master's degree? 

And if you go directly into a PhD after the B.S., which countries support it? In India(my country), it is nearly impossible other than you join a integrated course.

Is it same everywhere?
In general, applying for a Ph.D. program in life sciences with just a bachelor's degree is possible in at least some of the US universities (I do not know, however, to which extent this affects your chances at acceptance).  

E.g. the Harvard medical school web site says "Minimal requirements include a bachelor’s degree and undergraduate preparation in the sciences."