Do I need to know now what I'm majoring in?

You don't need to formally declare your major until you reach 30 credit hours, but there are some majors that will take very careful planning to fit into your Nine Semesters in Residence.  These typically include the sciences.  If you are seriously considering majoring in Biology or Biochemistry then you will want to declare this major as soon as possible and begin with Biology for Science Majors (BIOL 112) as soon as possible.  Be aware that an appeal is possible, if needed, once you have completed a MAP with an advisor after you arrive on campus.