The basic eligiblity criteria is that you should have passed your 10+2 in science subjects. Few Institutiins conduct Entrance Examination for admission while few Institutions conduct admissions based on merit of the marks scored in your 10+2. Few Institutions require you to score only pass marks in any of the subjects on your 10+2. So, with your 10+2 in Biology, you can pursue B.Sc Computer Sciences.