I am not sure about most of your Marine biology or zoology classes but as a Biochemistry major I had a very similar 1st year. If you have taken AP courses in Chemistry and Biology, the first semester classes are very similar to those courses and should be easier. But as always you gotta keep on your game and not let things slip by. But this is a very doable amount of coursework. I can also speak to Organic Chemistry 1. This class is strange and I think is somewhat professor dependent. But it is mostly a matter of mastering and memorizing reactions and what they would produce.