Hey Shivani,
Dont worry for most programs in Biology you dont need MS to join PhD.... Except in Europe, other places (mostly US ) are quite flexible in this requirement.... And first of all, try to generate a small list of universities based on your research interest...Don't just go on the brand name...Look for your interests. Typically Ivy League Schools are a tough nut to crack... try--www.usnews.com, for getting names of various US universities and their respective rankings....However don't select the universities based on the rankings, use them as a starting point....