Department of Biological Sciences
Asked Questions About Biology from GS students & Transfer Students
Last update 08/24/2021


Q1: What should I take first, biology or chemistry?

Take general chemistry first. See Q3 for the rationale.

Q2: I am premed, and never took college level bio before. What biology class should I take?

If you are a postbaccalaureate student, or a student in SPS, you should take Bio. UN2401-UN2402. If you need to fulfill the lab requirement for medical school, you should take the lab Bio UN2501. You can take the lab either term; we advise taking it after you complete UN2401.

If you are a CC or GS undergraduate, you should take Bio UN2005-2006 instead of UN2401-UN2402. You do NOT have to take UN2501. There are many other ways to fulfill the lab requirement for the major -- see the major requirements page for details.

Note that chemistry is a prerequisite for Bio UN2005 or UN2401, so you should take general chemistry first. (See Q3 for the rationale behind this.)

See Q5 for details of UN2005 vs. UN2401. If you have a problem with the number of points, and need to take the 'other class' for more or less points (4 for UN2005 vs 3 for UN2401) please contact the DUS, Dr.  Mowshowitz, dbm2 at

Q3: Why do I have to take chemistry before biology?

A3: There is a big difference between most college science courses and most high school science courses. In high school, you are usually expected to memorize the basic facts and principles. In college, you are expected to learn the facts in much more detail and you are also expected to understand the principles in much greater depth (this is usually the hard part). This means (in practical terms) that on exams you are asked to apply the principles that you have learned to solve problems and to explain totally new situations. This is just as true of biology as it is of physics and chemistry -- college biology is an experimental science, not a descriptive science. If you jump straight into Biology UN2005/UN2401 without a year of college chemistry to help you "rev up" you are likely to find the biology overwhelming. You may review this exam from a past year of UN2005 and review your answers with the exam key. This will give you an idea of what makes UN2005/6 a unique Intro Bio sequence.
It also pays to take chemistry first for another reason. Most students who take biology need to take chemistry (eventually). If you are going to take chemistry anyway, you might as well take it first so that the molecular parts of bio will make more sense. Biologists use chemistry as language, the way physicists use math. You can explain physics without math, but it takes a lot longer and the explanations are not as satisfying, or you have to teach the math as you go along. So it is simpler to just do the math first and the physics after. Similarly, it makes more sense to do the chemistry first and the biology second.

Q4: I took introductory biology somewhere else. Should I start with UN2005/UN2401or should I skip UN2005 and start with a higher level (3000 level) course?

A4: Transfer students are required to start with UN2005/UN2401.  (For the difference between the two courses see Q5.)   Intro bio here is required because most students in the past who skipped it found themselves struggling in upper level (3000 level) courses. If you repeat a year of intro bio, you should still receive transfer credit toward graduation for the year of intro you took elsewhere.  However, the previous intro will not count toward your bio or bio related major at CU.  There are exceptions, but they must be approved in advance by an advisor from the biology department. If and only if your intro course was at a rigorous institution, and included a heavy dose of genetics and biochemistry, AND you did well (& remember it), you may be able to skip UN2005. If you learned a lot of cell biology & physiology, you may be able to skip UN2006. However, in virtually all cases, you will need to take intro bio here. Why? Because UN2005/UN2006 goes deeper and demands more thought and application of knowledge than the usual introductory college bio course (or AP course). The course covers less topics than usual, but each topic is covered in great detail. There is more stress on problem solving and less on memorization. You may review this exam from a past year of UN2005 and review your answers with the exam key. This will give you an idea of what makes UN2005/6 a unique Intro Bio sequence. Additionally, a recent edition of the Learner's Manual (aka Problem Book) should be available in the science library. If you look at all the available material, and still believe you should be able to skip UN2005/6, you need to get written permission from an advisor in the biology department.  Only students who have taken an unusually rigorous intro course elsewhere will be granted exceptions. If you plan to ask for an exception, we suggest you register for either UN2005/UN2401 or a 3000 level course and attend both courses for the first week of class. Once you decide which course is the right level, you can drop or add courses as necessary.

Q5: What is the difference between Bio UN2005 and Bio UN2401?

A5: Short answer: Not much -- there is a single CW web site for both classes.

Long answer:
The lectures in Bio UN2005 and UN2401 are identical and the overall work load in the two courses is the same. However the amount of time a student is required to spend in class (or on Zoom)  is different. This is because UN2005 has required recitations (with weekly quizzes) and UN2401 has optional recitations (no quizzes). Because of the required recitation, Bio UN2005 is 4 points while Bio UN2401 is 3 points. The same similarities and differences apply to Bio C2006 vs. UN2402.
UN2401 has optional recitations because it is assumed that many adult students:
    (1) have less time available to 'attend' recitations because of jobs and family responsibilities,
    (2) do not want to pay for the extra point, and
    (3) have had more practice at pacing themselves and are less likely to allow themselves to fall behind.

The exams in the two courses and the grading scales for the exams are the same - the scale is set using the scores of the UN2005 (undergraduate) students. Therefore the exam scores needed to earn an A are exactly the same in each class. However the percentage of A's in each class is often different because the composition of the two classes is not the same. 
Undergraduates in GS &CC should take UN2005, and postbacs and special students must register for UN2401.
* (Note that all exams in both classes, except the final, will be given in the late afternoon or at night.) Students from either class may attend either set of lectures; students can switch back and forth as their schedules change (or they oversleep) or even go twice a day if they want. However, UN2005 students must attend UN2005 recitations and UN2401 students may attend only UN2401 recitations. The recitation sections for UN2005 are listed separately on the directory of classes -- Students in UN2005 must sign up for a section (called UN2015, no points) with the registrar. UN2401 students do not sign up; times and rooms for the optional UN2401 sections will be posted after school starts. All recitations start the second week of classes.

If you need additional information,  contact the instructors and/or see the UN2005/UN2401 CW web site which includes notes from last year's lectures, a sample exam, contact info for the instructors, etc.

*If you have a problem with the number of points, and need to take the 'other class' for more or less points (4 for UN2005 or UN2006 vs 3 for UN2401 or UN2402) please contact the DUS, Dr.  Mowshowitz, dbm2 at

For additional information for undergraduates, go to the Biology Department Undergraduate Page.

For FAQs for First Year Students and Prospective Students, go to