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2026 QCE 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 exam median and average: not stated in QCAA's report.
13,961 students completed Units 3 and 4 across the General and alternative sequences. The General exam was worth 101 raw marks and contributed 50% of the subject result.
Only 10.03% got the meiosis question right. I've gone through last year's report and marking guide. These are the questions I'd redo.
The percentages are published results. QCAA doesn't give written-question averages, so those sections explain where an answer misses the marking criteria, not how many students made each mistake. This covers the General paper.
Paper 1, Q5: Meiosis
1 mark. 10.03% correct.
Where students went wrong: 34.76% chose 46 chromosomes and two gene copies. Another 31.84% chose 23 chromosomes and two copies.
What they should have done: Choose 46 chromosomes and four copies. At metaphase I, DNA has replicated but homologous chromosomes haven't separated. Each chromosome has two sister chromatids. For an autosomal gene, the two homologous chromosomes carry four copies between them. DNA replication doesn't halve the chromosome count.
Paper 1, Q25c: Molecular evidence versus appearance
2 marks.
Where an answer loses marks: Saying DNA is more accurate without explaining why similar-looking species might not be closely related.
What you needed: Distinguish convergent and divergent evolution. Related species can share inherited structures, but unrelated species can evolve similar features under similar selection pressures. That makes appearance alone an unreliable guide to relatedness.
Paper 1, Q26c: Natural selection
3 marks.
Where an answer loses marks: Repeating the graph or saying the organisms adapted, without explaining how.
What you needed: Explain variation in body length, differential survival and reproduction, and change across generations. Larger organisms had an advantage in the conditions shown, survived and reproduced more successfully, and passed on the relevant alleles. Those alleles became more common over generations. Individuals didn't grow bigger because they needed to.
Paper 2, Q1b: Bottlenecks and genetic drift
2 marks.
Where an answer loses marks: Defining a bottleneck without explaining the effect on allele frequencies.
What you needed: A bottleneck sharply reduces population size. The small surviving sample can have very different allele frequencies by chance. Don't turn a question about genetic drift into survival of the fittest.
Paper 2, Q4: Transcription factors
3 marks.
Where an answer loses marks: Saying different genes are switched on without explaining how, or leaving out the example.
What you needed: Transcription factors bind to specific DNA sequences and regulate gene expression. Different expression patterns allow cells to specialise. An example is the SRY-encoded protein regulating genes involved in testis development. The example had its own mark.
For 2026, perusal time is five minutes instead of ten. You also need to explain how isolation affects gene flow and can lead to speciation, rather than just name the types.
Use the 2025 report alongside the official marking guide. 2026 syllabus changes.
Figures and criteria: QCAA. Explanations paraphrased from its materials, © State of Queensland (QCAA) 2025–2026, CC BY 4.0.
Use the Biology hub and past papers and marking guides alongside this.
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