Biological science is a demanding major, but not in the way most people expect. The coursework itself starts deceptively simple, leaning heavily on memorization in introductory classes, then ramps up sharply as you move into upper-level courses that require chemistry, calculus, and lab work on top of biology content. About 20% of students who start as biology majors switch to a non-STEM field by their second year, the highest switch rate among STEM disciplines at universities that have tracked this data closely.
Whether biology feels “hard” depends a lot on what kind of hard you’re prepared for. Here’s what actually makes the major challenging and what you can realistically expect.
The Memorization Problem in Early Courses
Introductory biology has a reputation for being a memorization marathon, and the data backs that up. A study published in CBE Life Sciences Education analyzed nearly 10,000 exam questions from 50 introductory biology instructors across different institutions. A striking 93% of those questions tested only the two lowest levels of thinking: recall and basic comprehension. Less than 1% required anything above straightforward application.
This means your first year of biology rewards a very specific skill: absorbing and retaining large volumes of terminology, processes, and classification systems. If you’re someone who does well with flashcards and repetition, introductory biology may feel manageable. If you’re someone who thrives on problem-solving and struggles with pure memorization, those early courses can feel like a grind. Many faculty argue students need this factual foundation before tackling harder thinking, but there’s little evidence that front-loading memorization actually prepares students for higher-level work.
The shift hits in upper-level courses, where you’re suddenly expected to interpret data, design experiments, and connect concepts across disciplines. Students who coasted on memorization in introductory courses often struggle when the thinking demands change.
It’s Not Just Biology You Have to Learn
The biggest surprise for many biology students is how much chemistry, math, and physics the degree requires. A typical biology major includes two semesters of general chemistry with labs, one or two semesters of organic chemistry with labs, a semester of biochemistry, one to two semesters of calculus or statistics, and at least one semester of physics with a lab. Students on a pre-med or research track often take the longer sequence in each of these, meaning two full semesters of organic chemistry and calculus-based physics.
At Iowa State University, for example, biology majors complete a minimum of 12 credits of chemistry alone. That’s four courses before you even count the labs. For many students, organic chemistry or calculus becomes the bottleneck that slows their progress or pushes them to reconsider the major entirely. The difficulty of a biology degree isn’t just the biology; it’s carrying a full course load where half your classes are in adjacent STEM fields that each have their own steep learning curves.
Lab Work Adds Significant Hours
Lab courses are a core part of any biology degree, and they demand more time than the credit hours suggest. A standard rule of thumb is that one credit of lab work requires 3 to 4 hours per week in the lab itself. A 3-credit research course, then, means 9 to 12 hours weekly of hands-on work, not counting time spent writing up results or preparing for the next session.
This is on top of your lecture courses, problem sets, and studying. During semesters heavy in lab courses, biology students can easily hit 25 to 30 hours per week of class and lab time before any independent studying begins. Time management becomes just as important as intellectual ability. Students who work part-time jobs or carry other commitments often find the lab schedule especially difficult to navigate, since labs run at fixed times and can’t be rescheduled.
How Many Students Switch Out
Attrition data from the University of Delaware, tracking cohorts from 2007 to 2012, found that biological science majors had the highest dropout rate among all STEM categories. By the start of their second year, 20.1% of biology students had switched to a non-STEM major, compared to 13.3% across STEM fields overall. Another 6.9% had left the university entirely. Only about 73% were still persisting in a STEM major by that point.
These numbers reflect decisions made after just one year. The students who leave aren’t necessarily failing; many switch because the workload or subject matter didn’t match their expectations, or because the prerequisite chemistry and math courses proved more demanding than anticipated. The gap between what students imagine biology will be (animals, ecosystems, human health) and what the first year actually involves (cell chemistry, molecular structures, statistical methods) drives a lot of early departures.
What This Means for Pre-Med Students
A large number of biology majors choose the degree because they plan to apply to medical school. Biological science is by far the most common major among med school applicants, accounting for 57% of all applications. But here’s a counterintuitive finding: biology majors don’t have the highest acceptance rate. Their acceptance rate sits at 43.4%, while humanities majors get in at 51.8%, math and statistics majors at 52.3%, and physical science majors at 49.5%.
This doesn’t mean biology is a bad pre-med major. The lower acceptance rate likely reflects the sheer volume of applicants (over 30,000 biology majors applied in one recent cycle) and the fact that biology attracts many students who are less certain about medicine but default to the major anyway. Still, it’s worth knowing that a biology degree doesn’t give you a competitive edge in medical school admissions over other majors. If you’re choosing biology purely as a pre-med strategy rather than genuine interest, you may find the workload harder to sustain.
What Makes Biology Different From Other Hard Majors
Compared to engineering or physics, biology requires less advanced math but more breadth. You won’t take differential equations or linear algebra, but you’ll need working fluency in chemistry, physics, statistics, and biology simultaneously. Compared to humanities majors, biology demands far more scheduled class time (labs lock you into fixed blocks), more cumulative knowledge (each course builds directly on prerequisites), and less flexibility in course sequencing.
The type of difficulty also shifts throughout the degree. Early courses test your ability to memorize at volume. Mid-level courses, especially organic chemistry and biochemistry, test your ability to understand three-dimensional molecular interactions and reaction mechanisms. Upper-level biology courses test your ability to read primary research literature, design experiments, and think critically about data. Students who find one phase easy may hit a wall at another.
Biology is not the hardest STEM major by most metrics, but it’s consistently underestimated. Students who come in expecting it to be “easier than engineering” are often caught off guard by the chemistry requirements, the lab time commitment, and the sheer volume of material. The students who do well tend to be consistent studiers rather than crammers, comfortable with both memorization and analytical thinking, and realistic about the time the degree actually demands each week.