The USA Biology Olympiad (USABO) is one of the most rigorous science competitions available to high school students in the United States — and it is a direct pathway to the International Biology Olympiad (IBO) for the top performers. The competition tests biology knowledge at the college and university level, far beyond what standard AP Biology covers. Our free printable PDF gives you 2026 practice questions spanning the full USABO content spectrum: cell biology, molecular biology, biochemistry, genetics, plant biology, animal physiology, ecology, evolution, and ethology. Practice with the free USABO - USA Biology Olympiad practice test on PracticeTestGeeks (96 questions with answer explanations).
Whether you are preparing for the 50-minute Open Exam or targeting a top score on the 120-minute Semifinal, this PDF lets you study anywhere — at your desk, in a library, or wherever you do your best thinking. Download it once and use it as many times as you need.
Facts verified Nov 7, 2026 against Center for Excellence in Education. Dates that have passed are removed automatically.
Facts verified Nov 7, 2026 against Center for Excellence in Education. Dates that have passed are removed automatically.
| Item | Detail | Official source |
|---|---|---|
| Number of questions (Open Exam) | Multiple choice, one response per question; no guessing penalty | Center for Excellence in Education |
| Number of questions (Semifinal Exam) | Multiple choice, multiple true/false, and short answer | Center for Excellence in Education |
| Time limit (Open Exam) | 50 minutes | Center for Excellence in Education |
| Time limit (Semifinal Exam) | 120 minutes | Center for Excellence in Education |
| Exam fee (School) | $125 flat fee per school (covers all its students) | Center for Excellence in Education |
| Retake policy | Can take the Open Exam every high school year; IBO attendance limited to twice | Center for Excellence in Education |
| Delivery | Online exam, proctored in person at a registered school or authorized USABO Test Center | Center for Excellence in Education |
| Eligibility (Semifinal Exam) | Top 10% of Open Exam scorers who are U.S. citizens or green-card holders | Center for Excellence in Education |
| Next exam date (National Finals) | June 20–30, 2027 (in person only) | Center for Excellence in Education |
| Registration deadline (School) | November 15, 2026, 11:59 PM ET | cee.org |
| Registration deadline (Student) | November 22, 2026, 11:59 PM ET | cee.org |
| Testing window (Practice Exam) | January 8–22, 2027 | Center for Excellence in Education |
Facts verified Nov 7, 2026 against Center for Excellence in Education. Dates that have passed are removed automatically.
Interactive USABO - USA Biology Olympiad resources on PracticeTestGeeks, free to start:
The USABO Semifinal and IBO exams draw from university-level biology across nine major content areas. The Open Exam tests a broad cross-section of the same material at a slightly lower depth. Here is what you need to master for each domain.
Expect detailed questions on membrane structure and function (fluid mosaic model, membrane proteins, transport mechanisms), signal transduction pathways (receptor tyrosine kinases, G-protein coupled receptors, second messengers), the cell cycle (G1/S/G2/M phases, checkpoints, cyclins and CDKs), mitosis and meiosis in complete mechanistic detail, and organelle function including the detailed machinery of the endomembrane system and mitochondrial structure.
DNA replication (origins, helicases, primase, leading and lagging strand synthesis, Okazaki fragments, proofreading), transcription and translation in both prokaryotes and eukaryotes, gene regulation at every level (operon model for prokaryotes, enhancers, silencers, transcription factors, chromatin remodeling for eukaryotes), and biotechnology methods including PCR, gel electrophoresis, Southern/Northern/Western blotting, CRISPR-Cas9 mechanism, and recombinant DNA techniques are all fair game.
Enzyme kinetics questions require you to interpret Michaelis-Menten curves, calculate Km and Vmax, and understand competitive versus non-competitive inhibition. Metabolic pathway questions cover glycolysis (substrates, products, ATP yield, regulation), the TCA cycle (intermediates, enzyme names, NADH/FADH2 production), the electron transport chain (complexes I–IV, proton gradient, chemiosmosis), oxidative phosphorylation (ATP synthase mechanism), and both the light reactions and the Calvin cycle of photosynthesis in mechanistic detail.
Mendelian and non-Mendelian inheritance patterns, linkage and recombination frequency calculations, population genetics (Hardy-Weinberg equilibrium calculations, genetic drift, bottleneck and founder effects, natural selection mathematics), phylogenetics (reading and constructing cladograms, maximum parsimony), speciation mechanisms (allopatric, sympatric, parapatric), and the mathematical modeling of evolutionary change are all tested at the Semifinal level.
Plant anatomy (root, stem, and leaf structure; vascular tissue types — xylem and phloem), meristem types and their roles, hormone functions (auxin in phototropism and cell elongation, gibberellin in stem elongation and seed germination, cytokinin in cell division, ABA in stomatal closure and dormancy, ethylene in fruit ripening), the mechanistic details of both C3 and C4 photosynthesis, transpiration and water potential, and tropisms are all covered.
The nervous system (action potential generation and propagation, synaptic transmission, neurotransmitter types), the endocrine system (hormone classes, feedback loops, specific glands and their hormones), the adaptive and innate immune system (B cells, T cells, antibody structure, MHC molecules, complement), circulatory system (cardiac cycle, blood pressure regulation, capillary exchange), and renal function (nephron structure, filtration, reabsorption, secretion, countercurrent multiplication) are all high-frequency Semifinal topics.
Population dynamics (logistic and exponential growth, carrying capacity, predator-prey oscillations), community ecology (competition, mutualism, succession), energy flow (trophic levels, ecological efficiency), nutrient cycles (nitrogen, carbon, phosphorus), conservation biology concepts, and animal behavior (classical and operant conditioning, imprinting, kin selection, Hamilton rule for altruism, honest signaling) round out the content coverage.
Many readers pair this guide with the usabo past exams to check their readiness before exam day.
The PDF is a powerful study resource, but the best USABO preparation combines offline review with timed online testing. Our USABO practice test platform offers randomized question sets drawn from all nine content domains, with answer explanations that go beyond the correct answer to build the deep mechanistic understanding the Semifinal demands. Use the PDF to diagnose your weakest areas, then return to the online tests to drill those topics under exam-like time pressure.
| Pros | Cons |
|---|---|
| Validates your knowledge and skills objectively | Study materials can be expensive |
| Increases job market competitiveness | Exam anxiety can affect performance |
| Provides structured learning goals | Requires dedicated preparation time |
| Networking opportunities with other certified professionals | Retake fees apply if you don't pass |
Try these questions from our free USABO - USA Biology Olympiad practice tests. The correct answer and an explanation follow each question.
What is the relationship between theory and practice in USA Biology Olympiad immunology and disease?
Answer: A. Theory provides the foundation and framework that guides effective practical application
Theory and practice are complementary: theoretical knowledge provides the conceptual framework and understanding that guides effective, evidence-based practical application in professional settings.
What is a best practice in USA Biology Olympiad immunology and disease?
Answer: A. A method or technique recognized as superior based on evidence and expert consensus
Best practices are methods, techniques, or approaches that are recognized through evidence, research, and expert consensus as producing superior results and are recommended for adoption.
What is the primary objective of immunology and disease in USA Biology Olympiad?
Answer: A. To ensure competence and proficiency in core immunology and disease concepts
The primary objective of immunology and disease knowledge is to ensure practitioners have the competence and proficiency needed to perform effectively and safely in their professional roles.
Which approach is most effective for mastering immunology and disease in USA Biology Olympiad?
Answer: A. Combining theoretical study with practical application and regular review
The most effective approach combines theoretical understanding with practical application, reinforced by regular review and assessment, enabling deeper comprehension and long-term retention.