Is IGETC required for a biology major?

The schools that I’m shooting for are UCLA, UCI, and UCSD. I hear from one counselor that IGETC is required/recommended and then another counselor says that I just need to focus on the major preparatory courses. The UC site says to just focus on the major preparatory classes for STEM majors so should I just follow that? Will the UC’s accept partial IGETC?