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: 60
Time: 120 min
Authority: QCAA
Updated: 2026-05-29

Open the official PDF ->Official marking notes

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

60 marks in 120 minutes (about 2 min/mark), with perusal time before writing. The paper has two parts:

Section 1 - Multiple choice: about 20 marks. Budget roughly 30 minutes (~1.5 min each), flagging and returning to hard items.
Section 2 - Short response: about 40 marks, mixing short-answer calculations/explanations with longer extended-response items. Budget roughly 85 minutes, leaving ~5 minutes to check.

Use perusal time to scan Section 2 and identify the highest-mark extended responses so you can pace them. For a multi-mark explain item, plan three or four linked points so each marking criterion is addressed.

Worked practice questions (exam-style)

Worked example

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 $a$ for the recessive allele, both parents are heterozygous carriers $Aa \times Aa$ (1 mark). A Punnett square gives a $\tfrac{1}{4}$ ( $25\%$ ) chance of an affected child each pregnancy, and the affected son is $aa$ (1 mark).

Worked example

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).

Worked example

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, $\text{CO}_2$ 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

Sit Section 1 in 30 minutes, then Section 2 in ~85 minutes under exam conditions. Mark strictly against the official QCAA marking guide and the marker report (linked in the frontmatter above) - 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.

Use this paper well

Sit the paper under exam conditions (120 minutes, 60 marks).
Mark yourself against the official QCAA marking notes.
Compare against the Biology hub to find the syllabus dot points this paper tested.

What this paper assessed

Structure and timing

Worked practice questions (exam-style)

Common errors students made

How to use this paper

Use this paper well

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