HSC Biology exam (NESA): format, marking and multiple choice

The HSC Biology exam set by NESA is one 100-mark paper with 5 minutes of reading time and 3 hours of working time. Section I is 20 multiple-choice questions for 20 marks (about 35 minutes). Section II is 80 marks of written answers, written straight into an answer booklet (about 2 hours 25 minutes). You need a NESA-approved calculator, and there's no formula sheet or data sheet to bring or be given.

This guide describes the Biology Stage 6 exam (2017 syllabus) as set in the 2023, 2024 and 2025 HSC, and applies to students sitting the Year 12 external exam. For every past paper by year, go to HSC Biology past papers (NESA).

What is the format of the HSC Biology exam?

All three papers we hold (2023, 2024 and 2025) share one skeleton. The instructions on the front page of each say the same thing, and the figures below come straight from them.

Reading time is 5 minutes, and working time is 3 hours on top of that. Section I plus Section II adds to exactly the 3 hours, so there's no spare time hidden anywhere. NESA's rules say reading time is for reading only: no writing, no highlighters and no marking the paper. The printed start time on the timetable is when reading time begins. Rules like that, and the rest of the exam-room routine, are in how to prepare for HSC exams.

Two details change how you handle the booklet:

• The Section II instructions tell you to answer in the spaces provided, and that "these spaces provide guidance for the expected length of response". The ruled lines are a length hint from the examiners.
• Extra writing space is at the back of the booklet. If you use it, you have to say which question you're answering.

Equipment. NESA's equipment list names a NESA-approved calculator for Biology and nothing else, and every paper's front page repeats it. None of the 2023, 2024 or 2025 papers carries a formula sheet, data sheet or Periodic Table.

When is the HSC Biology exam?

Biology is a morning exam. In the 2026 written exam period it sat on Wednesday 21 October, starting at 9.25 am and finishing at 12.30 pm, which is 5 minutes of reading plus 3 hours of working time. The HSC exam preparation guide covers the full 2026 series.

What does the HSC Biology exam cover?

Across the 2023, 2024 and 2025 papers, our mapping of every question to its syllabus dot point places the marks in the Year 12 modules, Module 5 (Heredity), Module 6 (Genetic Change), Module 7 (Infectious Disease) and Module 8 (Non-infectious Disease and Disorders), and in the working scientifically skills:

• Heredity: 24.7%
• Genetic Change: 22.5%
• Infectious Disease: 20.9%
• Non-infectious Disease and Disorders: 18.3%
• Working scientifically skills: 13.5%

These shares are of the 299 marks (of 300) that map to a dot point, and the mapping is ours, not NESA's. The topic-by-topic and dot-point breakdown, and how the balance moved between 2023 and 2025, are in HSC Biology most tested topics. Where students drop marks is in HSC Biology hardest topics.

How are the 80 Section II marks spread across questions?

Section II questions aren't equal in size, and the count of questions changes by paper.

Many questions have parts. In 2025, Question 30 was an 11-mark question: part (a) was 4 marks to describe a process for producing mosquitoes that express a protein, and part (b) was 7 marks to evaluate the statement that genetic technologies are beneficial to society.

Section II works out at about 1.8 minutes a mark (145 minutes for 80 marks). A 7-mark part is about 13 minutes, and a 2-mark part is under 4. Use that to tell when you're overwriting a small question or underwriting a big one.

How is Section II marked?

Each part is marked against a ladder of criteria in NESA's Marking Guidelines. The guidelines are published with the paper, so you can read the exact ladder for any past question. Here are the two ladders for Question 30 on the 2025 paper:

Source: NESA, 2025 HSC Biology Marking Guidelines, Question 30. Criteria wording is NESA's.

Four things show up across the 2025 guidelines, not just in this question.

1. The key word sets the top rung. In Q30(a) a description earns 4 and an outline earns 3. In Q28(c), explaining the role of memory cells earns 3 and outlining it earns 2. In Q29(b), explaining two procedures earns 4, while describing them, or explaining one, earns 3. NESA defines outline as sketching the main features in general terms, describe as giving characteristics and features, and explain as relating cause and effect (why or how). If you only outline when the question says explain, the ladder tops you out a mark early.
2. Judgement is a criterion. In Q30(b) the rungs from 5 marks up require a judgement, and Q25's 3-mark rung asks for an accurate evaluation of a product statement. When the key word is evaluate, finish with a clear call and keep it consistent.
3. Stimulus use is marked. The top three rungs of Q27 (a 6-mark comparison of internal and external fertilisation) each require reference to the data provided, from "limited" at 4 marks up to "incorporates references" at 6. A correct answer that ignores the table or graph can't reach the top.
4. There's nearly always a 1-mark floor. By our count, 23 of the 24 criteria tables in the 2025 guidelines give a mark for "provides some relevant information". Every part is worth attempting.

NESA's own note on the page that publishes these guidelines says the sample answers are not intended to be exemplary or even complete answers. They show the expected nature and scope of a response. Treat them as a calibration of length and content, not as a script.

How often each key word is asked is in the same three papers. Parts carrying explain account for 19.3% of the marks, describe 14.0% and evaluate 11.0%. Parts with more than one key word count under each, so the shares overlap. HSC Biology hardest topics shows how AusGrader users score on each verb.

Multiple choice

Section I is 20 questions, 1 mark each, with four options. At about 35 minutes it works out to 1.75 minutes a question.

NESA's Marking Feedback covers Section II only. It says nothing on any Section I question in 2024 or 2025, so there's no board commentary on multiple choice to lean on. What the papers do show is a mix of three question styles:

• Straight recall. 2024 Question 1 asks which of four groups of pathogens is non-cellular. You know it or you don't.
• Classify from a description. 2025 Question 6 describes a person given an injection of antibodies after a bite and asks what type of immunity results.
• Read the stimulus. 2023 Question 3 gives a Punnett square with numbered cells, Question 5 an experimental table for binary fission in E. coli, and 2025 Question 7 a table of an animal's body temperature against air temperature before asking you to pick the type of animal and the reason. Some of these have options in two columns (a type and a reason, or blood before and after dialysis in 2025 Question 9), so both halves of the row have to be right.

Working through them:

• Bank time on recall questions. If you know it, answer and move on. The minutes you save go to the table and diagram questions.
• Answer from the stimulus first. On a table, graph or diagram question, work out what the data shows before you read the options, so the options don't steer you.
• Check both halves of a two-column option. Cover the reason column, decide on the type, then check the reason supports it.
• Answer every question. An unanswered question can't score.

On AusGrader, across 55,432 marked multiple-choice attempts on HSC Biology questions from board papers, users average 73.0%, against 68.4% across 11,018 short-answer attempts. These are self-selected users practising without exam timing, so treat the gap as a pointer to where practice is easiest, not as a NESA result. The full breakdown is in HSC Biology hardest topics.

What do markers say costs marks in Section II?

NESA's general feedback for 2024 and 2025 was identical, and it fits every question on the paper: read the question for all its parts, understand the key word and its requirements, plan the response, use scientific terms, engage with the stimulus, show working with units in calculations, be logical and succinct, and review the answer against the question. The question-by-question feedback adds specifics. These are the patterns that repeat, in our words.

Confusing near-neighbours. Markers flagged the same confusions across two years: external fertilisation versus asexual reproduction, self-pollination versus asexual reproduction, reliability versus validity versus accuracy, somatic versus germline mutations, and a disease caused by environmental exposure versus one caused by a pathogen or by genetics.

Imprecise terms and notation. In 2025 Question 31, answers used "recessive" where the pedigree needed "autosomal recessive", and used allele letters (such as S and s) that look alike on the page. In 2024 Question 28, answers gave a probability two ways that contradict each other, such as a quarter and 33%.

Calculations and graphs. In 2024 Question 29, working was missing on the graph and the percentage calculation, and graph type, plotting and scale reading cost marks.

What do weak and strong answers look like?

Pairs drawn from the NESA feedback, rewritten in our words.

How should I practise for the HSC Biology exam?

Do the papers under timing, and mark them against the guidelines, not against memory. A sensible routine:

1. Sit Section I in about 35 minutes, then check against the answer key.
2. For Section II, give each part the time its marks imply (about 1.8 minutes a mark), and write inside the lines.
3. Mark each part against its ladder. Note which rung you landed on and which criterion you missed: a missing judgement, a missing data reference, or the wrong key word.
4. Redo the weakest part from a different year on the same topic.

AusGrader's HSC Biology page holds the questions from these papers by year and by topic, with the marking criteria attached, so you can practise a single part and see the ladder straight away. HSC Biology most tested topics shows which dot points to start with.