I am a graduate student planning to apply in Australia for a PHd very soon. I have observed that most of the universities require the applicant to provide a 100-words summary of the research they propose to undertake. Now my graduate training was fairly general (MS doesn't really help you specialize). I am very clear on the field in which I want to pursue PHd (Mathematical Biology), However the field is very wide in scope and I have not really narrowed down to a specific problem to which I want to dedicate the next four years of my life. So my question is: what level of detail is being expected on such a "100-words summary"? Are recent graduate students really expected to have a project in mind they want to work on? (Am I finding this incredible only because I dont have one?) Should I may be give an example of the kind of problems that excite me, while indicating my flexibility to be engaged in something new? I vaguely understand that I should consider the area of work of the person I am writing to while preparing such an application, but more than that, I am not sure I understand.
Possibly related question http://mathoverflow.net/questions/27001/research-statement-in-phd-applications-how-much-is-too-much
But I believe I am asking a different question. Also, as further clarification to one of the answers given below, my MS did not involve writing a thesis. (If it did, that would certainly serve as a good starting point.)