As a Biology student, you likely spend lots of time on the second floor of the Walker Science Building. There are LOTS of opportunities on the bulletin boards that line the hallways. Plan to arrive to class early or hang out for a bit after class to browse all the fliers posted.
You may learn of opportunities through announcements in your classes. Be sure to prick up your ears to catch any and all announcements made at the start of class!
When the time comes for you to look for an internship position, talk to your professors and/or your advisor. Many times, they can point you to certain sources for internship opportunities that may be of interest to you. Other times, they may have personal contacts or "inside information" that can help you find a position in a certain sub-field of biology or a certain location. You may have contacts yourself that you haven't considered. Learning how to use the resources available to you is an important stepping stone in your career. Talk to your professors. They can help you learn how to use the tools you have!