WACE Biology: Continuity of species and Surviving in a changing environment

The WACE Biology exam

SCSA's design brief for Year 12 Biology gives three sections, and the last one lets you choose: you answer one of two questions from each unit.

Multiple-choice questions can use stimulus such as diagrams, tables and graphs. In Section Two the parts of each question usually get harder as you go and can ask you to respond to second-hand data or recent research. Extended answers can include labelled diagrams with notes, lists of points joined by linking sentences, tables, graphs or annotated flow diagrams, so the format is yours to choose. Up to three calculators that cannot store programs or text are allowed. Unlike Chemistry and Physics, the brief lists no data booklet.

Unit 3 and Unit 4 in the syllabus

Unit 3: Continuity of species

The unit starts with heredity: DNA structure and replication, transcription and translation, mutation, and how meiosis, crossing over and random assortment create variation. You predict genotype and phenotype frequencies with Punnett squares, including co-dominance, incomplete dominance, sex-linked alleles, multiple alleles and polygenes, and you read pedigree charts. It then moves to evolution: the evidence (genomes, protein sequences, fossils, anatomy and embryology), phylogenetic trees, natural selection, and changes in allele frequency through mutation, genetic drift (including the founder effect) and gene flow. Selective breeding and allopatric speciation are named too.

Unit 4: Surviving in a changing environment

This unit covers homeostasis as a stimulus-response model with negative feedback, thermoregulation in endotherms and ectotherms, nitrogenous waste and water balance, and the adaptations of xerophytes and halophytes. The infectious disease content groups pathogens into bacteria, fungi, protists and viruses, and uses Western Australian examples such as jarrah dieback and the amphibian chytrid fungus. It asks why a disease spreads (pathogen growth, host density, mode of transmission) and how it is controlled by quarantine, herd immunity, breaking the life cycle, antibiotics and antivirals.

The Genetics and DNA course is a good foundation for the heredity half of Unit 3, and the Human Physiology course introduces homeostasis.

Worked examples

A sex-linked cross

Red-green colour blindness is carried on the X chromosome as a recessive allele. A woman who is a carrier (X^(N)Xⁿ) has children with a man with normal vision (X^(N)Y). The Punnett square gives four equally likely children: X^(N)X^(N) (daughter, normal), X^(N)Xⁿ (daughter, carrier), X^(N)Y (son, normal) and XⁿY (son, colour blind).

The chance that a child is a colour-blind son is 1 in 4, or 25%. The chance that a son is colour blind is 1 in 2. Reading which of the two is being asked is where marks go, and no daughter can be colour blind in this cross because she always receives X^(N) from her father.

Why a disease spreads

A short-answer question might give a graph of cases in a school and ask why the curve rose quickly in week 3. Link the cause to the factors in the syllabus: a pathogen population that grew once it was in a dense host population, a mode of transmission that works at close range, and no immunity in the group. Then name one control that targets that factor, such as isolating infected students or immunisation to build herd immunity.

Check your inheritance reasoning in the Genetics and DNA course, then press Mark:

School marks and the ATAR

For Year 12 Biology, SCSA fixes the school-based weightings: a science inquiry investigation 20%, extended response 10%, tests 20% and examinations 50%. Schools report an A to E grade and a school mark out of 100. Statistical moderation then places school marks on the same scale as the exam, the two are averaged into the combined mark, and TISC calculates the ATAR from your ATAR courses. WACE also has a separate Human Biology ATAR course with its own exam, held on Thursday 5 November in 2026, so check which one you are enrolled in.

Dates

Use the daily paper as a trial

Your school sets its own trial exam, and SCSA does not publish one. The free daily paper on the Year 12 Biology track is a short timed trial: 8 questions, 25 to 35 marks, marked as you go. It is not a three-hour WACE paper.

• It matches: inheritance, gene expression, evolution and speciation, populations and gene technology appear in its rotation and line up with Unit 3.
• It mostly does not match Unit 4: its rotation leans on respiration, photosynthesis, nervous coordination, muscle contraction and the kidney, none of which is named in the WACE Year 12 content. Homeostasis days will help, but infectious disease and Western Australian case studies you will need to revise from your notes.
• Year 11: the Year 11 Biology paper is useful for cell structure and transport that Unit 3 assumes.

Exam answers

The answers and worked mark scheme come with each daily paper once it has been marked. They are Uni-Sine's own, never official SCSA answers or past paper solutions.

Mistakes that cost marks

• Answering "probability the child is affected" when the question asks "probability a son is affected".
• Describing natural selection as individuals changing. Allele frequencies in the population change.
• Using "adapt" for a single organism's response when the question asks about evolution over generations.
• Writing a long extended answer with no labels. Examiners accept diagrams and tables, and they are quicker.

Read next

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