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WACE Biology: complete 2026 guide to Year 12 ATAR Units 3 and 4

A complete 2026 guide to WACE Year 12 ATAR Biology (Units 3 and 4). How the 50 percent school assessment and 50 percent external written examination combine, what Unit 3 (continuity of species) and Unit 4 (surviving in a changing environment) cover, and links to every dot-point answer we have written.

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WACE ATAR Biology is the Year 12 sequence made of Unit 3 (Continuity of Species) and Unit 4 (Surviving in a Changing Environment), set by the School Curriculum and Standards Authority (SCSA). Both units are examinable in the single external written examination at the end of the year.

This page is the index. Below you will find how the course is assessed, what each unit covers, and links to every dot-point answer we have written for WACE Year 12 Biology.

How WACE Biology is assessed in 2026

The ATAR Biology course result is built from two equally weighted halves.

School assessment: 50 percent. Set and marked by your school against the SCSA assessment table for Biology. It combines science inquiry skills (practical investigations, fieldwork, data analysis and evaluation), topic tests, and school examinations across Units 3 and 4. School marks are statistically moderated against the external examination so that schools are compared fairly.

External examination: 50 percent. A single written paper set and marked by SCSA, sat at the end of Year 12. It covers both Unit 3 and Unit 4 and usually has three sections: multiple choice, short answer, and extended answer. Expect data interpretation, diagrams and extended written responses.

Your two halves are combined after moderation to produce the final course mark that TISC then scales into your ATAR.

Unit 3: Continuity of Species

Unit 3 develops the molecular and population biology of inheritance and change.

DNA, genes and chromosomes
Nucleotide structure, the genetic code, transcription and translation, and how DNA is packaged into chromosomes.
Mitosis and meiosis
The stages of each division, their roles, and how meiosis generates variation through crossing over, independent assortment and random fertilisation.
Genetic variation and inheritance
Mendelian patterns, alleles and genotypes, and the sources of variation in populations.
Evolution and speciation
Natural selection, allele frequency change, genetic drift, gene flow, and how reproductive isolation produces new species.
Biotechnology and its applications
Restriction enzymes, recombinant DNA, PCR, gel electrophoresis, transgenic organisms and cloning, with their benefits and implications.

Unit 4: Surviving in a Changing Environment

Unit 4 builds the physiology of staying stable and the biology of disease.

Homeostasis in animals
Negative feedback, thermoregulation, osmoregulation and blood glucose control coordinated by the nervous and endocrine systems.
Homeostasis in plants
Stomatal control of water balance, the role of guard cells and abscisic acid, and tropisms.
Pathogens and disease
Types of pathogen, how they cause harm, and the modes of transmission of infectious disease.
The immune response
The three lines of defence, the humoral and cell-mediated specific responses, memory cells and types of immunity.
Epidemiology and disease control
Epidemics and pandemics, transmission, herd immunity, and the strategies used to control the spread of disease.

Our 2026 WACE Biology dot-point answers

Every link below is a focused answer to one SCSA Biology dot point. Each page identifies the dot point, gives the worked answer with diagrams and a worked example, and flags the most common mistakes.

Unit 3: Continuity of Species

Unit 4: Surviving in a Changing Environment

How to use this hub

If you are starting Unit 3 this term: read the DNA, genes and chromosomes dot point first, then mitosis and meiosis. They underpin inheritance, evolution and biotechnology later in the unit.

If you are revising for a genetics test: work through genetic variation and inheritance, then practise Punnett squares and pedigree analysis until they are automatic.

If you are starting Unit 4: read homeostasis in animals first, because the negative feedback model recurs in plant homeostasis and again when you study fever and immune regulation.

If you are weeks from the external examination: revise the full Unit 3 set, because half the paper draws on it, then consolidate Unit 4. Practise past SCSA papers under timed conditions, focusing on extended-response and data-interpretation questions.

The system around WACE Biology

WACE Biology sits inside the wider WACE ATAR system administered by SCSA. For the official syllabus, assessment outline and past ATAR examination papers, refer to scsa.wa.edu.au.

Every guide on this hub was written by ExamExplained (an initiative of Better Tuition Academy and XLev) and is independent of SCSA.

The WACE system, explained

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Common questions about Biology

How is WACE Year 12 ATAR Biology assessed in 2026?
The ATAR Biology course is assessed 50 percent school assessment and 50 percent external written examination set and marked by SCSA. The school assessment combines science inquiry (practical and investigative work), tests, and examinations across the year. The external examination is a single written paper at the end of Year 12 covering both Unit 3 and Unit 4. Your final mark is the average of your school mark and your examination mark after statistical moderation.
What does WACE Biology Unit 3 cover?
Unit 3 is "Continuity of Species". It covers the structure of DNA, genes and chromosomes, mitosis and meiosis and how meiosis generates variation, patterns of inheritance and genetic variation, the mechanisms of evolution and how new species form (speciation), and biotechnology techniques such as PCR, gel electrophoresis and recombinant DNA along with their applications and implications.
What does WACE Biology Unit 4 cover?
Unit 4 is "Surviving in a Changing Environment". It covers homeostasis in animals (thermoregulation, osmoregulation and blood glucose control through negative feedback), homeostasis in plants (stomatal control of water balance and tropisms), the types and transmission of pathogens, the immune response and immunity, and epidemiology and the strategies used to control the spread of disease.
How is the WACE Biology external examination structured?
The external ATAR examination is a single written paper of about three hours plus reading time. It typically has three sections: multiple choice, short answer, and extended answer. It draws on both Unit 3 and Unit 4, so genetics and evolution content from earlier in the year remains examinable alongside homeostasis and disease. Diagrams, data interpretation and extended written responses are all assessed.
Is WACE Biology required for university courses?
Biology is a prerequisite or strongly recommended for many WA university courses including nursing, health sciences, biomedical science, environmental science, agriculture, and pathways into medicine and allied health at UWA, Curtin, Murdoch and ECU. Always check current course prerequisites with TISC and the individual universities.
How does WACE Biology scale for the ATAR?
SCSA scaling adjusts Biology marks relative to the achievement of the cohort across all their courses. Biology is a large, popular course and historically scales close to the middle of the science subjects. Final scaling varies each year and is applied by TISC when calculating the ATAR, so the most reliable strategy is to maximise your raw achievement.
What's the difference between mitosis and meiosis?
Mitosis produces two identical diploid cells (for growth and repair). Meiosis produces four genetically distinct haploid cells (for sexual reproduction).
How does protein synthesis work?
Transcription (DNA → mRNA in the nucleus) then translation (mRNA → polypeptide at the ribosome). tRNA brings amino acids that the ribosome links into the protein sequence the mRNA codes for.
What's homeostasis?
The maintenance of a stable internal environment (temperature, blood glucose, pH) despite external change — usually via negative feedback loops involving receptors, control centres, and effectors.
How does evolution by natural selection work?
Variation exists in a population → some variants survive and reproduce better in a given environment → those traits become more common over generations. Requires heritable variation, differential reproductive success, and time.
What's the difference between an antibody and an antigen?
Antigen: a molecule (often on a pathogen) that triggers an immune response. Antibody: a Y-shaped protein the immune system makes to bind specifically to that antigen.