QCE Biology 2022
Walkthrough of the 2022 QCE biology exam: what it assessed, strategy tips, and the common errors flagged in the official marker report.
- Marks
- 87
- Time
- 180 min
- Authority
- QCAA
- Updated
This paper was set on the 2019 QCAA syllabus. From the 2026 external assessments the 2025 syllabus applies, so some content and the exam format have changed. It is still useful practice, but check the current QCAA Biology syllabus and QCAA's 2026 key changes before relying on it. The total marks at the top of this page are QCAA's published total for this year's papers (check the marking guide), and the time shown is two papers of 90 minutes working time. Marks and question types vary, so use QCAA's own paper.
What this paper assessed
The QCAA Biology external assessment (Paper 2 of the course, worth 50% of the subject) covers Units 3 and 4. The 2022 paper assessed:
- Unit 3 - Biodiversity and the interconnectedness of life: describing and classifying biodiversity, ecosystem dynamics, population ecology, and the effects of environmental change.
- Unit 4 - Heredity and continuity of life: DNA structure and replication, gene expression (transcription and translation), inheritance and pedigree analysis, mutation and biotechnology, natural selection and speciation, and the evidence for evolution.
Items spanned the QCAA cognitions - recall, applying understanding to unfamiliar scenarios, and analysing/interpreting data. Several questions presented a novel diagram, graph or experimental table and asked students to apply known principles, and the paper rewarded precise terminology and explicit cause-and-effect reasoning.
Structure and timing
QCAA sets the external assessment as more than one paper, and the number of marks, the sections and the question types differ from year to year. Open the official paper for the exact structure of this year; the marks and time shown at the top of this page are a guide only.
- Pace by marks. Share your working time in proportion to the marks on offer, so a 6-mark item gets about three times the time of a 2-mark item. Flag any multiple choice item that runs long and return to it.
- Use perusal time. Scan for the data-heavy items and the longest calculations or extended responses so you can plan them early.
- Subject habits. For a multi-mark explain or evaluate item, plan three or four linked points so each marking criterion is addressed, and keep a few minutes at the end to check that every explain or justify answer gives a reason, not just a description.
Worked practice questions (exam-style)
Question 1 (4 marks): Pedigree analysis
A pedigree shows two unaffected parents with an affected son and an unaffected daughter. Determine the most likely mode of inheritance, justify it, and state the parents' genotypes.
Solution. Two unaffected parents producing an affected child means the allele is recessive (the parents are carriers) - 1 mark. To decide autosomal vs X-linked recessive: an affected son could arise either way, but the simplest consistent explanation with an unaffected father is autosomal recessive (an X-linked recessive son inherits the allele only from a carrier mother, which is still possible, so examine the rest of the pedigree; absence of a clear sex-bias here favours autosomal) - 1 mark for autosomal with reasoning. Using for the recessive allele, both parents are heterozygous carriers (1 mark). A Punnett square gives a () chance of an affected child each pregnancy, and the affected son is (1 mark).
Question 2 (6 marks): Natural selection
A population of insects is exposed to a new pesticide. Initially most insects die, but over several generations the population recovers and the pesticide becomes ineffective. Explain this change using the theory of natural selection.
Solution.
- Variation: within the original insect population there is genetic variation, including rare alleles conferring some resistance to the pesticide (1 mark).
- Selection pressure: the pesticide acts as a selective agent, killing susceptible individuals while resistant individuals are more likely to survive (1 mark).
- Differential reproduction: surviving resistant insects reproduce and pass the resistance alleles to offspring (1 mark).
- Change in allele frequency: over successive generations the frequency of the resistance allele increases in the population (1 mark).
- Outcome: the population becomes predominantly resistant, so the pesticide is no longer effective (1 mark).
- The key point: the pesticide did not create resistance - it selected for pre-existing variation; resistance was not acquired in response to exposure (1 mark).
Question 3 (5 marks): Experimental design and data
A student investigates whether light intensity affects the rate of photosynthesis by counting oxygen bubbles from pondweed at several distances from a lamp. Identify the variables and explain two improvements to the validity and reliability of the investigation.
Solution. The independent variable is light intensity (distance from the lamp); the dependent variable is the rate of oxygen bubble production; controlled variables include water temperature, availability, the species and mass of pondweed, and time interval (2 marks). To improve validity, control temperature with a water bath/heat sink between lamp and plant, so any change is attributable to light intensity and not heating (1 mark). To improve reliability, repeat the count at each distance multiple times and average, reducing the effect of random error (1 mark). A valid conclusion must describe only the trend in the data (e.g. "rate increased as intensity increased, then plateaued") rather than overreaching beyond what was measured (1 mark).
Common errors students made
The 2022 QCAA marker report flagged that students frequently confused antigen and antibody, mixed up the steps of transcription and translation, gave conclusion statements that ignored the data shown, and often failed to identify the independent and dependent variables in experimental questions. Add these recurring traps:
- "Need/want" language in natural selection - saying organisms adapted because they needed to rather than describing selection of pre-existing variation.
- Transcription/translation muddle - placing translation in the nucleus, or confusing the roles of mRNA, tRNA and codon/anticodon.
- Vague terms - writing "things" or "stuff" instead of named molecules, structures and processes.
- Conclusions beyond the data - inferring causation from a single trial or stating a general claim instead of the specific measured trend.
How to use this paper
The 2022 sitting was two papers of 90 minutes working time each, with 10 minutes of perusal in the booklets. QCAA's 2026 timetable has two papers, each with 5 minutes of perusal and 90 minutes of working time (check the current QCAA syllabus for your sitting). Sit one paper at a time under timed conditions, pacing each by marks. Mark strictly against the official QCAA marking guide and the marker report (linked at the top of this page) - these state the exact language and criteria markers rewarded. Rework one extended response per week, re-planning it as four linked points each addressing a criterion. Keep a running glossary of paired terms you confuse (antigen/antibody, transcription/translation, variation/adaptation) and self-test it before each practice sitting.