I want to know that if the work presented as a poster in a symposium should be a work in progress or could it be a published work or submitted paper? The field I am concerned with is biophysics.
I am not in biophysics - I'm in the health and social sciences, so this may be different for you. However, I would saw that it depends on the situation. Rirwt, some conferences have specific policies against presenting material that has been previously published. So, presenting a paper that has already been published may be frowned upon (thought I've been to many conferences with this policy and have seen presentations that have been previously published papers). The main concern is duplicate publication. So, if your conference fully-publishes the works that are presented (papers, posters), then publishing a finished product in both the conference proceedings and a journal article may be frowned upon by the conference.
Now, if you are presenting a work in progress and it will be different than a future or past published paper or presentation, that is usually acceptable. I have done this and have used the audience comments to help with revisions or with ideas for turning the paper into a second paper with a different focus.