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2026 VCE Biology exam: What to learn from last year's mistakes
Hi all, in preparation for the upcoming exam, here's what to learn from last year's mistakes.
2025 median exam grade: C+. VCAA does not publish an exact median mark.
Average: 71.75/120, or 59.8%. VCAA reports 143.5/240; this is converted to the exam's 120-mark scale.
14,700 students assessed. 8.3% received A+. The 2025 A+ cutoff was 208/240, equivalent to 104/120. That is last year's cutoff, not a prediction for 2026.
Figures: VCAA's 2025 grade distribution, written examination on page 3: source.
The 2025 examiner report: source gives multiple-choice percentages but no written-question averages. The written mistakes below are identified in its feedback, not ranked by an unpublished mark. Percentages are rounded. My examples illustrate the fixes; they are not full model answers.
A21: Competitive inhibition
34% chose the correct answer, D. 43% chose A.
Where students went wrong: The most popular option put the active site on the wrong molecule. ATP is the product, not the enzyme.
What they should have done: Identify the enzyme and substrates before deciding what an inhibitor blocks.
ATP synthase has the active site. ADP and inorganic phosphate are used to produce ATP. If a competitive inhibitor prevents ADP binding, less ADP is converted and it can accumulate. Follow the reaction rather than picking the molecule whose name looks familiar.
A29: Reading the antibody graph
27% chose the correct answer, A. 69% chose B.
Where students went wrong: They treated the rise in antibody concentration as the day of first exposure.
What they should have done: Allow for the delay in the primary immune response.
Antibodies only began increasing on day 13. That does not mean exposure happened on day 13. Activation and expansion of the relevant lymphocytes take time. Of the options given, day 2 was the exposure date consistent with that delay.
B3b: Photorespiration and temperature
Where students went wrong: They wrote about enzyme denaturation or said the plant binds oxygen without identifying Rubisco.
What they should have done: Explain which molecule binds to Rubisco and why that changes under the conditions given.
At higher temperatures, stomatal closure can reduce carbon dioxide availability. Oxygen is then more likely to bind to Rubisco, increasing photorespiration in C3 plants. Denaturation is a different explanation: a permanently altered active site would prevent normal binding of either gas.
B3c(i): Saying a variable is controlled
Where students went wrong: They wrote that all plants received the same light or water. The question asked how to control both.
What they should have done: Describe an action the students could actually carry out.
Place every plant the same distance from the lamp and expose them for the same duration. Measure an equal volume of water for each plant and give it at the same time. That describes the control method. Saying to keep the amount equal does not.
B5b: Extracellular does not mean outside the body
Where students went wrong: They confused extracellular pathogens with pathogens outside the body, then compared lines of defence. Others gave similarities when asked to contrast.
What they should have done: Compare the adaptive responses to pathogens outside cells and pathogens inside cells.
Plasma cells produce antibodies that bind antigens on extracellular pathogens. Cytotoxic T cells target infected body cells and induce apoptosis. Compare those mechanisms directly. Both pathogens can be inside the body; the relevant difference is whether they are inside its cells.
B6b: Why vaccinate the mother again?
Where students went wrong: They claimed memory cells pass from mother to baby, or gave a generic booster explanation without mentioning either person.
What they should have done: Connect the mother's renewed antibody response to the protection the baby receives.
Antibody levels can fall between pregnancies. A booster can increase the mother's antibody levels so sufficient antibodies can pass to the next baby, providing passive protection against RSV. The baby receives antibodies, not the mother's memory cells.
B7b: What creates the DNA differences?
Where students went wrong: They identified natural selection or genetic drift as the process producing new DNA differences. Others skipped the identification entirely.
What they should have done: Name mutation first, then explain how selection can affect the new alleles.
A mutation changes a bee's DNA sequence and can produce a new allele. If that allele improves survival and reproduction in the new environment, carriers may leave more offspring. Over generations, the allele can become more common. Selection changes which variants spread; it does not create the original mutation.
Try B3c(i), B5b and B7b before reading their report sections. Check whether you explained the mechanism asked for, or just named the topic.
Use the VCE Biology hub and past papers and examiner reports alongside this.
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