BIOL 102/3.0 and BIOL 103/3.0 (Biology: see What BIOL course should I take?)
CHEM 112/6.0 (see first year Chemistry)
MATH 121/6.0 or MATH 120/6.0 (calculus: see What MATH course should I take?)
PHYS 117/6.0 or PHYS 106/6.0 or PHYS 104/6.0 (Physics: see What PHYS course should I take?)
For a list of electives see here