HSC Biology most tested topics
Across the three NESA Biology external papers from 2023 to 2025, Genetic Technologies carries 9.0% of the marks against 0.3% for Conducting Investigations, so the paper rewards Genetic Technologies more than any other topic. At dot-point level 9.5.1 carries 6.9% of paper marks, and 21 of the 73 dot points that the board assesses externally have not appeared in one of these papers. Every percentage below covers the 99.7% of marks that map to a syllabus dot point.
Computed from 3 NESA Biology external papers, 2023 to 2025: 104 questions, 134 question parts and 300 marks.
Module, topic and dot-point shares below are of the 299 marks that map to a dot point, so each of those tables adds to 100%. 55 of the 134 parts are assessed against more than one dot point, and their 155 marks are divided evenly between the dot points they cover.
What these papers are
| Year | Exam | Questions | Marks |
|---|---|---|---|
| 2025 | Exam | 34 | 100 |
| 2024 | Exam | 35 | 100 |
| 2023 | Exam | 35 | 100 |
Marks by module
| Module | Share of marks |
|---|---|
| Module 5: Heredity | 24.7% |
| Module 6: Genetic Change | 22.5% |
| Module 7: Infectious Disease | 20.9% |
| Module 8: Non-infectious Disease and Disorders | 18.3% |
| Module 9: Working Scientifically Skills | 13.5% |
Marks by topic
| Topic | Share of marks | Papers it appears in | Years |
|---|---|---|---|
| Genetic Technologies | 9.0% | 3 of 3 | 3 of 3 |
| Mutation | 8.8% | 3 of 3 | 3 of 3 |
| Immunity | 8.7% | 3 of 3 | 3 of 3 |
| Analysing Data and Information | 7.2% | 3 of 3 | 3 of 3 |
| Genetic Variation | 6.9% | 3 of 3 | 3 of 3 |
| Causes of Infectious Disease | 6.7% | 3 of 3 | 3 of 3 |
| Reproduction | 6.5% | 3 of 3 | 3 of 3 |
| DNA and Polypeptide Synthesis | 6.0% | 3 of 3 | 3 of 3 |
| Homeostasis | 6.0% | 3 of 3 | 3 of 3 |
| Technologies and Disorders | 5.8% | 3 of 3 | 3 of 3 |
| Prevention, Treatment and Control | 4.8% | 3 of 3 | 3 of 3 |
| Biotechnology | 4.7% | 3 of 3 | 3 of 3 |
| Epidemiology | 4.5% | 3 of 3 | 3 of 3 |
| Cell Replication | 4.0% | 3 of 3 | 3 of 3 |
| Planning Investigations | 2.5% | 3 of 3 | 3 of 3 |
| Problem Solving | 1.5% | 3 of 3 | 3 of 3 |
| Processing Data and Information | 1.5% | 3 of 3 | 3 of 3 |
| Inheritance Patterns in a Population | 1.3% | 1 of 3 | 1 of 3 |
| Causes and Effects | 1.0% | 2 of 3 | 2 of 3 |
| Prevention | 1.0% | 1 of 3 | 1 of 3 |
| Responses to Pathogens | 0.7% | 2 of 3 | 2 of 3 |
| Communicating | 0.5% | 1 of 3 | 1 of 3 |
| Conducting Investigations | 0.3% | 1 of 3 | 1 of 3 |
Marks by dot point
Dot-point numbers and wording are NESA's own. Where a dot point is written as a list, its items run together here separated by semicolons.
| Dot point | Content | Topic | Share of marks | Papers |
|---|---|---|---|---|
| 9.5.1 | ● derive trends, patterns and relationships in data and information | Analysing Data and Information | 6.9% | 3 of 3 |
| 5.1.1 | ● explain the mechanisms of reproduction that ensure the continuity of a species, by analysing sexual and asexual methods of reproduction in a variety of organisms, including but not limited to: – animals: advantages of external and internal fertilisation – plants: asexual and sexual reproduction – fungi: budding, spores – bacteria: binary fission (ACSBL075) – protists: binary fission, budding | Reproduction | 5.9% | 3 of 3 |
| 5.3.2 | ● model the process of polypeptide synthesis, including: (ACSBL079) – transcription and translation – assessing the importance of mRNA and tRNA in transcription and translation (ACSBL079) – analysing the function and importance of polypeptide synthesis (ACSBL080) – assessing how genes and environment affect phenotypic expression (ACSBL081) | DNA and Polypeptide Synthesis | 5.7% | 3 of 3 |
| 7.3.2 | ● explain how the immune system responds after primary exposure to a pathogen, including innate and acquired immunity | Immunity | 5.2% | 3 of 3 |
| 8.1.2 | ● investigate the various mechanisms used by organisms to maintain their internal environment within tolerance limits, including: – trends and patterns in behavioural, structural and physiological adaptations in endotherms that assist in maintaining homeostasis (ACSBL099, ACSBL114) – internal coordination systems that allow homeostasis to be maintained, including hormones and neural pathways (ACSBL112, ACSBL113, ACSBL114) – mechanisms in plants that allow water balance to be maintained (ACSBL115) | Homeostasis | 5.2% | 3 of 3 |
| 5.4.2 | ● model the formation of new combinations of genotypes produced during meiosis, including but not limited to: – interpreting examples of autosomal, sex-linkage, co-dominance, incomplete dominance and multiple alleles (ACSBL085) – constructing and interpreting information and data from pedigrees and Punnett squares | Genetic Variation | 5.0% | 3 of 3 |
| 6.2.1 | ● investigate the uses and applications of biotechnology (past, present and future), including: (ACSBL087) – analysing the social implications and ethical uses of biotechnology, including plant and animal examples – researching future directions of the use of biotechnology – evaluating the potential benefits for society of research using genetic technologies – evaluating the changes to the Earth’s biodiversity due to genetic techniques | Biotechnology | 4.7% | 3 of 3 |
| 5.2.1 | ● model the processes involved in cell replication, including but not limited to: – mitosis and meiosis (ACSBL075) – DNA replication using the Watson and Crick DNA model, including nucleotide composition, pairing and bonding (ACSBL076, ACSBL077) | Cell Replication | 4.0% | 3 of 3 |
| 8.5.2 | ● investigate technologies that are used to assist with the effects of a disorder, including but not limited to: (ACSBL100) – hearing loss: cochlear implants, bone conduction implants, hearing aids – visual disorders: spectacles, laser surgery – loss of kidney function: dialysis | Technologies and Disorders | 3.6% | 3 of 3 |
| 7.3.1 | ● investigate and model the innate and adaptive immune systems in the human body (ACSBL119) | Immunity | 3.5% | 3 of 3 |
| 8.3.3 | ● evaluate the method used in an example of an epidemiological study | Epidemiology | 3.5% | 2 of 3 |
| 7.1.1 | ● describe a variety of infectious diseases caused by pathogens, including microorganisms, macroorganisms and non-cellular pathogens, and collect primary and secondary-sourced data and information relating to disease transmission, including: (ACSBL097, ACSBL098, ACSBL116, ACSBL117) – classifying different pathogens that cause disease in plants and animals (ACSBL117) – investigating the transmission of a disease during an epidemic – design and conduct a practical investigation relating to the microbial testing of water or food samples – investigate modes of transmission of infectious diseases, including direct contact, indirect contact and vector transmission | Causes of Infectious Disease | 3.2% | 3 of 3 |
| 6.1.2 | ● compare the causes, processes and effects of different types of mutation, including but not limited to: – point mutation – chromosomal mutation | Mutation | 2.8% | 3 of 3 |
| 6.3.3 | ● investigate and assess the effectiveness of cloning, including but not limited to: – whole organism cloning – gene cloning | Genetic Technologies | 2.5% | 3 of 3 |
These 14 dot points carry 61.7% of the paper marks between them. Another 38 assessed dot points share the rest, and 21 of the 73 externally assessable dot points have not been assessed in any of these 3 papers. Content that has not appeared is still examinable.
What has moved between papers
Comparing the 2023 papers with the 2025 papers, six topics have moved by more than 3.0 percentage points.
| Topic | 2023 share | 2025 share | Movement |
|---|---|---|---|
| Mutation | 5.9% | 12.5% | up 6.6 points |
| Immunity | 7.1% | 12.0% | up 4.9 points |
| DNA and Polypeptide Synthesis | 7.1% | 1.5% | down 5.6 points |
| Epidemiology | 7.6% | 4.5% | down 3.1 points |
| Cell Replication | 1.5% | 6.0% | up 4.5 points |
| Inheritance Patterns in a Population | 3.9% | 0.0% | down 3.9 points |
How the papers are built
Short answer carries 80.0% of the marks across these 3 papers.
| Question type | Share of marks | Marks | Parts |
|---|---|---|---|
| Short answer | 80.0% | 240 | 74 |
| Multiple choice | 20.0% | 60 | 60 |
| Verb | Share of marks | Marks | Parts |
|---|---|---|---|
| explain | 19.3% | 58 | 17 |
| describe | 14.0% | 42 | 12 |
| evaluate | 11.0% | 33 | 6 |
| justify | 7.0% | 21 | 6 |
| compare | 6.3% | 19 | 5 |
| outline | 6.0% | 18 | 9 |
| design | 2.3% | 7 | 1 |
| discuss | 2.3% | 7 | 1 |
What these percentages do not tell you
Where to practise
Every topic above links to its own page of real NESA questions with marking criteria and average scores attached: Genetic Technologies, Mutation, Immunity, Analysing Data and Information, Genetic Variation, Causes of Infectious Disease, Reproduction, DNA and Polypeptide Synthesis, Homeostasis, Technologies and Disorders, Prevention, Treatment and Control, Biotechnology, Epidemiology, Cell Replication, Planning Investigations, Problem Solving, Processing Data and Information, Inheritance Patterns in a Population, Causes and Effects, Prevention, Responses to Pathogens, Communicating and Conducting Investigations. For how students actually score on this content, read HSC Biology hardest topics, and for the full question bank start at HSC Biology.
Frequently asked questions
Which topic carries the most marks in the HSC Biology external exam?
Genetic Technologies carries 9.0% of the marks across the 3 NESA papers from 2023 to 2025, ahead of Mutation on 8.8%.
How are marks split between question types in the HSC Biology exam?
Short answer carries 80.0% of the marks and multiple choice carries 20.0% of the marks, measured across 3 papers and 300 marks from 2023 to 2025.
Has the topic balance changed in recent HSC Biology papers?
Yes. Mutation moved up 6.6 percentage points, Immunity moved up 4.9 percentage points, DNA and Polypeptide Synthesis moved down 5.6 percentage points, Epidemiology moved down 3.1 percentage points, Cell Replication moved up 4.5 percentage points and Inheritance Patterns in a Population moved down 3.9 percentage points between the 2023 and 2025 papers.
How many past papers is this HSC Biology analysis based on?
3 NESA external papers from 2023 to 2025, covering 104 questions and 300 marks. 0.3% of those marks carry no dot-point mapping and sit outside the percentages.
Sources
- HSC Biology Examination, NESA, 2025. 3 papers, 2023 to 2025, covering 104 questions and 300 marks. Listed individually in the table at the top of this guide. Dot-point numbering follows the current NESA Biology syllabus.
Syllabus and assessment material referenced in this guide is used under licence, © Copyright NSW Education Standards Authority. See our NESA licensing notice. The NSW Education Standards Authority (NESA) does not endorse this product or service. NESA takes no responsibility for any errors in the reproduction of NESA Materials. Any sample examination papers or model answers accompanying the NESA Materials are not part of the NESA Materials and are in no way endorsed or authorised by NESA.
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