If they are not working on precisely your desired topic, they probably would know some others on campus with an interest closer to yours. Other departments in the Biological Sciences also have lists of their faculty research interests. Location of departmental offices may be found under Timetable Department listings. With a quick library search, you can locate most recent papers of possible research mentors. This will give you a good picture of precisely the sort of questions and work an individual is pursuing.
Many researchers have home pages on the web.
You may introduce yourself through a short letter, email or phone call requesting a meeting with the researcher. A research mentor is most interested in students who want to work in their area and are committed to follow through on a project. This initial request for a meeting might include times you are available to meet B Monday morning, Tuesday and Thursday afternoons. Be sure to include your email address, telephone number, etc. Have several prospective research mentors in mind.