QCE Biology was completed by almost 14,000 Queensland students in 2025, and its external assessment is worth 50% of your final result. The 2025 exam tested classification, evolution, genetic drift, non-disjunction, transcription factors and population growth, and QCAA's subject report shows exactly where students gained and lost marks.
This guide breaks down the external assessment section of QCAA's 2025 Biology subject report. It covers how every multiple-choice question was answered across the state, the short-response questions QCAA singled out, what effective responses did and QCAA's advice for future students. For the school-based side of the subject, see our companion breakdown of the 2025 QCE Biology internal assessments.
Key Takeaways
- 13,961 students completed Units 3 and 4 in 2025, and 99.53% received a C or higher.
- An A required a final mark of 87 or more out of 100. 31.98% of students achieved an A and 47.99% a B.
- The multiple-choice section was hard: students averaged only 55.9%, and 9 of the 20 questions were answered correctly by fewer than half the cohort.
- Question 5 was the hardest question: only 10.03% of students chose the correct answer.
- QCAA wants students to practise describing and explaining concepts under exam conditions, use terminology precisely and build confidence with numeracy, such as rearranging equations and calculating percentages.
The 2025 Cohort at a Glance
| Statistic | 2025 |
|---|---|
| Schools offering Biology | 449 |
| Students who completed Unit 1 | 16,888 |
| Students who completed Unit 2 | 15,664 |
| Students who completed Units 3 and 4 | 13,961 |
| Students who completed all 4 units | 82.67% |
| Students who received a C or higher | 99.53% |
Source: QCAA Biology subject report, 2025 cohort.
Only 65 students received a D and none received an E, so almost every student who finishes Biology passes. The real competition is between a B and an A.
QCE Biology External Exam Structure
| Feature | Paper 1 | Paper 2 |
|---|---|---|
| Section 1 | 20 multiple-choice questions (20 marks) | Short-response questions (52 marks) |
| Section 2 | Short-response questions (29 marks) | – |
| Total | 49 marks | 52 marks |
The exam is worth 101 marks in total, which is converted to a mark out of 50 and makes up 50% of your final result. The other 50% comes from your three internal assessments: the data test (IA1, 10%), the student experiment (IA2, 20%) and the research investigation (IA3, 20%).
More than half the exam marks sit in Paper 2's short-response questions, so the ability to write clear explanations matters as much as content knowledge.
The most common external assessment results in 2025 fell between the mid 30s and mid 40s out of 50, peaking at about 37–40. Very few students scored 49 or 50.
💡 Get ready for the exam with our step-by-step guide on how to prepare for QCE external exams.
2025 Grade Boundaries and Results
| Grade | Final Mark (out of 100) | Number of Students | Percentage of Students |
|---|---|---|---|
| A | 87–100 | 4,465 | 31.98% |
| B | 71–86 | 6,700 | 47.99% |
| C | 50–70 | 2,731 | 19.56% |
| D | 20–49 | 65 | 0.47% |
| E | 0–19 | 0 | 0.00% |
Source: QCAA Biology subject report, 2025 cohort.
Your final mark is your internal assessment total (out of 50) plus your external assessment mark (out of 50). Final marks peaked between about 75 and 90, right around the A cut-off of 87.
Paper 1: Multiple-Choice Results
| Question | Correct Answer | % Correct | Most Common Wrong Answer |
|---|---|---|---|
| 1 | C | 81.83% | A (12.20%) |
| 2 | B | 57.91% | A (27.11%) |
| 3 | C | 45.98% | D (44.15%) |
| 4 | B | 52.97% | C (32.38%) |
| 5 | D | 10.03% | C (34.76%) |
| 6 | D | 47.52% | B (35.69%) |
| 7 | A | 41.30% | C (36.95%) |
| 8 | C | 39.00% | D (27.72%) |
| 9 | B | 58.99% | C (31.79%) |
| 10 | C | 42.08% | B (26.53%) |
| 11 | C | 76.67% | D (9.50%) |
| 12 | A | 56.93% | B (31.07%) |
| 13 | C | 83.54% | B (6.71%) |
| 14 | C | 55.52% | A (21.71%) |
| 15 | B | 74.93% | A (12.52%) |
| 16 | A | 42.50% | D (27.91%) |
| 17 | A | 65.45% | B (17.25%) |
| 18 | C | 49.44% | D (27.06%) |
| 19 | D | 48.13% | B (28.27%) |
| 20 | A | 86.72% | B (9.53%) |
Source: QCAA Biology subject report, 2025 cohort. Some students did not answer every question.
What the Multiple-Choice Results Show
- Question 5 was by far the hardest. Only 10.03% chose the correct answer, D. Options A, B and C were each chosen by more students than D, with C the most popular at 34.76%.
- Question 3 was a near coin toss between the correct answer, C (45.98%), and D (44.15%).
- Questions 6 and 7 each had a wrong option chosen by more than a third of students.
- Questions 1, 13 and 20 were answered correctly by more than 80% of students. These are marks you cannot afford to drop.
- Across the paper, students averaged 55.9%, so the typical student lost about 9 of the 20 multiple-choice marks. In several questions, a single wrong option drew a third of the cohort, which usually points to a common misconception rather than a careless slip.
💡 Check out why past papers are the best way to study for exams.
Short-Response Questions QCAA Highlighted
QCAA's report gave feedback and sample responses for nine short-response questions from the 2025 exam.
Paper 1, Question 21(a): Features of the Linnaean System
Students had to describe two key features of the Linnaean system of biological classification.
Effective responses gave an account of two features, for example:
- it is a hierarchy of taxonomic levels from broad to specific: kingdom, phylum, class, order, family, genus and species
- it was originally based on morphological (physical) features, with more closely related organisms sharing more features.
Paper 1, Question 21(b): Inferring Similarities Between Species
Students had to explain how the Linnaean system lets researchers infer similarities between species, using an example.
Effective responses explained that species classified in the same taxonomic group share certain traits, then gave an example. One sample noted that humans and dogs are both in class Mammalia, so researchers can infer that both have fur and are warm-blooded.
Key lesson: When a question says "using an example", the example is worth marks. Leaving it out caps your score.
Paper 1, Question 25(c): Molecular vs Anatomical Data
Students used their knowledge of convergent and divergent evolution to explain why molecular sequence data is often more accurate than anatomical data for working out how closely species are related.
Effective responses:
- distinguished between divergent evolution (related species with a common ancestor) and convergent evolution (unrelated species evolving similar features)
- explained that analogous structures produced by convergent evolution can make unrelated species look related, so anatomical data can be misleading, while molecular data reflects actual genetic relatedness.
Paper 1, Question 26(c): Natural Selection Over Geological Time
Using a graph of body length and ocean temperature, students used the principles of natural selection to explain the trend in body length of marine organisms.
Effective responses referred to all three of:
- phenotypic variation in body length within the population
- differential survival and reproduction: when ocean temperature fell, longer bodies gave a selective advantage, so those organisms survived and passed the trait on
- change over time, linked to the data (from about 5–15 cm to 20–30 cm).
Key lesson: Natural selection answers need every principle, linked to the context and data in the question.
Paper 2, Question 1: Genetic Drift After a Bottleneck
Students explained why genetic drift is usually high in populations affected by bottlenecks.
Effective responses recognised that a bottleneck sharply reduces population size, so the gene pool is smaller, some alleles are at very low frequency, and those alleles can easily be lost by chance if the few individuals carrying them do not reproduce.
Paper 2, Question 2(b): Non-Disjunction and Turner Syndrome
Students explained how an error in meiosis could have caused the condition shown in a karyotype.
Effective responses:
- identified the error as non-disjunction
- described non-disjunction: chromosomes or sister chromatids failing to separate, producing gametes with an extra or missing chromosome
- explained how a gamete with no sex chromosome fertilising a normal gamete produces a zygote with a single X: Turner syndrome (monosomy X).
Key lesson: QCAA praised responses that referred directly to the karyotype, not generalised statements about aneuploidy.
Paper 2, Question 4: Transcription Factors and Cell Differentiation
Students explained how transcription factors allow cells to differentiate, using an example.
Effective responses:
- recognised that transcription factors bind to specific DNA sequences to increase or decrease transcription
- explained that this allows different genes to be expressed in different cell types
- gave an example, such as the SRY transcription factor directing the development of male reproductive organs.
Paper 2, Question 9: Inferring Allopatric Speciation
Using graphs of gene flow and genetic difference over time, students inferred which populations underwent allopatric speciation.
Effective responses inferred populations A and B and justified it with evidence: gene flow suddenly dropped to zero and genetic difference then rose rapidly, consistent with a physical barrier separating the populations. The gradual decline in gene flow between the other populations did not fit allopatric speciation.
Key lesson: An infer answer needs a conclusion plus reasoning and evidence from the stimulus.
Paper 2, Question 10(e): Average Annual Population Growth Rate
Students used capture–recapture data to find the average annual growth rate of a fur seal population.
Effective responses showed full working:
- used the Lincoln index to estimate the 2025 population: N = (230 × 250) ÷ 2 = 28,750
- calculated the growth since 2000: (28,750 − 15,000) ÷ 15,000 × 100 = 91.67%
- divided by the number of years to get an average annual growth rate of about 3.67%.
Paper 2, Question 11(c): Mass Extinctions and Evolutionary Radiation
Students used the competitive exclusion principle to explain why mass extinctions are often followed by evolutionary radiation.
Effective responses stated that no two species can occupy the same niche at the same time, then explained that mass extinctions leave many niches unoccupied, so surviving groups diversify rapidly to fill them.
What Students Did Well
QCAA said the 2025 cohort responded well when they:
- identified unknown values from graphs
- interpreted data from graphs and tables, such as inferring species relatedness from molecular data, identifying genetic conditions from a karyotype, interpreting ecological field data and deciding whether a population had reached carrying capacity
- made simple calculations, such as using the Lincoln index or predicting population size from quadrat data
- showed knowledge of the enzymes involved in DNA replication
- showed understanding of species interactions.
Areas QCAA Wants Students to Improve
1. Describing and Explaining Under Exam Conditions
QCAA wants more practice writing descriptions and explanations, for example:
- describing key features of the Linnaean system
- describing how climax communities differ from pioneer communities
- describing the structure of plasmids and their role in making recombinant DNA.
2. Integrating Knowledge to Explain Phenomena
The best answers combine several ideas. QCAA listed examples such as molecular vs anatomical data, natural selection, genetic drift after bottlenecks and transcription factors in cell differentiation.
3. Using Terminology Precisely
QCAA flagged commonly confused pairs:
- sex chromosome vs sex cell
- population growth vs population growth rate
- negative feedback vs homeostasis.
4. Numeracy
Practise rearranging equations, calculating percentages and working out ratios. Show full working for multi-step calculations.
💡 Not sure what "describe", "explain" or "infer" are asking for? Read our complete guide to QCE cognitive verbs.
How to Prepare for the QCE Biology External Exam
- Practise multiple choice with stimulus. With an average of 55.9%, this is where many students lose easy marks. Read every option and check it against the data.
- Write timed short answers for describe, explain and infer questions, and check that each part of the question is answered.
- Use the mark value as a guide. A 3-mark explanation usually needs three linked ideas.
- Learn terminology pairs that are easily confused, and use them precisely.
- Practise calculations such as the Lincoln index, percentage change, growth rates and Simpson's diversity index.
- Link every answer to the stimulus provided, rather than writing general statements.
- Sit full past papers under timed conditions.
For more preparation:
- read our guide to getting an A in QCE Biology
- see our breakdown of the 2025 QCE Biology internal assessments
- check the QCE exam timetable 2026 for this year's exam dates
- learn how QCE subject scaling works.
Need Help With QCE Biology?
Our QCE Biology tutors work one-on-one with students to master the content, interpret data with confidence and write the precise, well-structured explanations QCAA markers look for.
Source: Queensland Curriculum & Assessment Authority, Biology subject report, 2025 cohort (January 2026).
