Hi Kateryna -- I am neither a UM alum, nor a bio major, nor did I march at a Div 1 school, but I'm the parent of a son who marched at Pitt for 4 years while studying engineering. And I don't know a lot about the flag section.
So here's what I know. UM is rigorous. It has an excellent academic reputation and please expect that you will have as difficult a course load as you wish. Marching in a Div 1 band is almost like a full-time job. I see that you are interested in flags, I don't know how much that will be different from what the instrumentalists schedule is -- the instrumentalists have daily rehearsals. The UM Flag site says there are 32 members with 24 block spots. So it's really important to them to have all 24 spots filled on the field -- so even if you make the squad, you'll be competing to be one of the 24 on game day.
On home game days, your entire day will be taken up with pre-game, game and post-game activities with the band. So your fall semesters will be very busy. But it's possible. After all, if it weren't, there wouldn't be anyone marching flags, would there?
So go ahead and tryout for flags, and take that first step. The director and section leader is there to help, and it's a great way to make new friends. Best of luck! Lisa