3 years of science vs 4 years of science?

I am not applying to any Ivy League schools but I am looking at some selective schools like Rice, Vanderbilt, and Emory? Is it really necessary to take 4 years of sciences. I am planning on doubling up an taking Physics Honors and Chemistry II Honors to give me a total of 4 years of science (biology and chemistry are the other two). Would it be better if I switched Chem II Honors with something like AP Psych (which I want to take and it has more credits?)

If you take 3 years of science, will it include all of biology, chemistry, and physics?

Not sure how valuable chemistry 2 honors would be if it is not a course that can lead to advanced placement in college chemistry courses, or if you do not intend to study anything in college that requires chemistry.

Check each school you plan to apply to and be certain to meet the required and/or recommended classes for applicants.

yes it would include all of biology, chemistry, and physics.