The normal workload for freshmen students is 13-15 units per quarter. After freshman year, 15 units per quarter is considered normal for a UCD student studying any kind of biology.
Of those 15 units, 2-3 courses are in their major and at least one course is a non-science course (see sample schedules). There is never a need to take over the 15 units per quarter and no more than about 10 or those units should be for your major.
A GE class in addition to your major courses with a freshmen seminar, PHE classes, or 1-2 units electives can get you to 15 units without overloading academically.
Graduate in Four
This workload represents the level required to graduate in 4 years. Many students like a slightly lighter workload their first quarter and registering in 13-15 units is acceptable. However, we do expect students to complete 45 units by the end of the first year. In subsequent years, students are expected to complete 15 units per quarter on average (but minimally averaging 13 units/quarter per academic year – i.e. at the Minimum Progress requirement pace). Please see the UC Davis General Catalog, page 72, or the Office of the University Registrar web site for additional information about minimum progress requirements
Doing Well Takes Time and Effort
The UCD academic experience is very different from your high school academic experience. To do well, you should plan to spend at least 40 hours a week attending classes and studying, i.e., a full-time job! With a balanced schedule established as outlined above you will be able to effectively transition to UCD and graduate in 4.