HSC Biology infectious and non-infectious disease (Modules 7 and 8): The 2026 guide

Study guide18 min readUpdated 25 May 2026

Quick answer

HSC Biology Modules 7 and 8 are typically the largest combined share of marks in recent papers (NESA does not publish fixed module weightings) and reward systematic factual mastery of pathogens, the immune response, named diseases, and homeostatic feedback loops, combined with the ability to evaluate disease management strategies. Memorise the named examples; draw the immune response and feedback loop diagrams; practise the extended-response patterns.

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What the two modules ask
Module 7: Infectious Disease
Module 8: Non-infectious Disease and Disorders
Common HSC Modules 7-8 traps
How Modules 7 and 8 are examined
Practice strategy
Check your knowledge

What the two modules ask

HSC Biology Modules 7 (Infectious Disease) and 8 (Non-infectious Disease and Disorders) are heavily examined and typically the largest share of marks combined in recent papers, though NESA does not publish fixed module weightings. They are among the most-marked modules in HSC Biology and the most heavily tested in extended-response questions.

The modules are about how the human body is affected by, defends against, and adapts to disease. Module 7 focuses on threats from outside the body (pathogens); Module 8 on threats that arise within (homeostatic failure, genetic disorders) and on the body's self-regulation.

Module 7: Infectious Disease

Pathogens

A pathogen is any agent that causes disease. The five main types:

Bacteria: Prokaryotic single-celled organisms with a cell wall. Reproduce by binary fission. Cause disease through toxins (e.g. tetanus from Clostridium tetani) or by physically damaging host cells (e.g. tuberculosis from Mycobacterium tuberculosis colonising the lungs). Treated with antibiotics targeting bacterial-specific structures (cell wall, ribosomes).
Viruses: Acellular particles consisting of genetic material (DNA or RNA) enclosed in a protein coat. Cannot replicate independently; must hijack host cell machinery. Examples: influenza (RNA virus), HIV (retrovirus, integrates into host DNA), SARS-CoV-2. Treatable with specific antivirals but generally not antibiotics.
Prions: Misfolded proteins that induce other proteins to misfold. No genetic material. Example: bovine spongiform encephalopathy (BSE, "mad cow disease"). Extremely resistant to denaturation.
Fungi: Eukaryotic multicellular or unicellular organisms. Often opportunistic (cause disease in immunocompromised hosts). Examples: tinea (athlete's foot, ringworm), Candida (thrush).
Parasites and protozoans: Multicellular (parasitic worms) or single-celled eukaryotic organisms. Example: malaria caused by Plasmodium (transmitted by Anopheles mosquito; multiple life cycle stages).

Memorise at least one specific named example per pathogen type, with the disease and the entry/transmission method.

Transmission and entry

Direct transmission. Person-to-person via touch, droplet, sexual contact.
Indirect transmission. Vectors (mosquitoes for malaria), contaminated water (cholera), contaminated food (Salmonella), airborne particles.

Portals of entry. Respiratory tract (most respiratory infections), digestive tract (food poisoning), urogenital tract, broken skin, blood (mosquito bites, needles).

Immune response

The body's response to pathogens has two integrated arms.

Innate (non-specific) response. First line of defence.

Physical barriers: skin, mucous membranes.
Chemical barriers: stomach acid (pH ~2), lysozyme in tears and saliva, antimicrobial peptides.
Inflammation: histamine release, vasodilation, neutrophil recruitment, swelling.
Phagocytosis: macrophages engulf and digest pathogens.
Natural killer cells: destroy infected cells.

Adaptive (specific) response. Second line, develops over days.

B lymphocytes produce antibodies that bind specific antigens. Antibodies neutralise pathogens or mark them for destruction.
T lymphocytes include cytotoxic T cells (destroy infected cells) and helper T cells (coordinate response via cytokines).
Memory B and T cells persist after infection, providing long-term immunity.

Vaccination triggers the adaptive response by exposing the immune system to a weakened, killed, or component form of the pathogen. The body produces memory cells without experiencing severe disease.

Clonal selection: only the B-cell whose surface receptor matches the antigen (B2) is selected; the clone differentiates into antibody-secreting plasma cells and long-lived memory B-cells.

Innate immunity peaks within hours; adaptive immunity rises from day 4 and produces the antibody titre plus a memory population for faster secondary responses.

Epidemiology and public health

Epidemiology is the study of disease distribution and determinants in populations. Key terms:

Incidence: new cases per unit time.
Prevalence: total cases at a point in time.
Mortality rate: deaths per population per unit time.
R0 (basic reproductive number): average number of secondary cases generated by one primary case in a fully susceptible population.

Public health responses: vaccination programs, antibiotic stewardship, quarantine and isolation, contact tracing, vector control, sanitation, public education.

Antibiotic resistance is a major modern concern. Resistance evolves when bacteria with random resistance mutations survive antibiotic exposure and pass the gene on. Strategies to slow resistance: prescribing only when necessary, completing the full course, developing new antibiotics, reducing agricultural antibiotic use.

Effective R falls linearly with vaccinated fraction. Marked thresholds (R = 1): influenza (R₀ = 2) at 50%, SARS-CoV-2 Omicron (R₀ = 8) at 87.5%, measles (R₀ = 15) at 93.3%. Formula: v_c = 1 − 1/R₀.

Module 8: Non-infectious Disease and Disorders

Homeostasis

Homeostasis is the maintenance of stable internal conditions despite changing external environments. The body uses negative feedback loops: a deviation from the set point triggers responses that restore the set point.

The four components of a feedback loop:

Stimulus (deviation from the set point)
Receptor (detects the stimulus)
Control centre (processes the signal, often in the brain or via hormones)
Effector (executes the response, restoring the set point)

Thermoregulation

The hypothalamus is the control centre. Normal core temperature: ~37°C.

If too cold: vasoconstriction (skin blood vessels narrow, reducing heat loss), shivering (muscle contraction generates heat), piloerection (in furred mammals; humans have residual goosebumps), increased metabolic rate.

If too hot: vasodilation (skin vessels widen, allowing heat loss to environment), sweating (evaporative cooling), decreased metabolic rate.

Blood glucose regulation

Pancreatic alpha and beta cells detect blood glucose.

If blood glucose rises (after a meal): beta cells release insulin. Cells take up glucose. Liver converts glucose to glycogen for storage. Blood glucose falls.

If blood glucose falls (between meals): alpha cells release glucagon. Liver breaks down glycogen into glucose. Blood glucose rises.

Diabetes mellitus is a failure of this system. Type 1: immune destruction of beta cells (no insulin produced). Type 2: cellular insulin resistance (insulin produced but cells don't respond). Both require management (Type 1 with insulin injections; Type 2 typically with diet, exercise, and oral medications).

Osmoregulation

Kidneys regulate water and salt balance. Antidiuretic hormone (ADH) increases water reabsorption when the body is dehydrated. Aldosterone increases sodium reabsorption. The kidney's nephron is the functional unit.

Non-infectious disease

Caused by factors other than pathogens:

Genetic disease: specific gene mutations. Examples: cystic fibrosis (CFTR gene, autosomal recessive), Huntington's disease (HTT gene, autosomal dominant), sickle cell anaemia (HBB gene, codominance).
Environmental disease: exposure to harmful agents. Examples: asbestos-induced mesothelioma, UV-induced melanoma, lead poisoning.
Nutritional disease: scurvy (vitamin C deficiency), beriberi (thiamine deficiency), iodine deficiency goitre, marasmus/kwashiorkor (protein-energy malnutrition).
Lifestyle/non-communicable disease: cardiovascular disease, Type 2 diabetes, many cancers. Linked to diet, exercise, smoking, alcohol use.

Disorders of the senses (hearing and vision)

Hearing: sound waves are detected by hair cells in the cochlea. Disorders include conductive hearing loss (problem in outer/middle ear), sensorineural hearing loss (cochlear or auditory nerve damage). Technologies: hearing aids, cochlear implants.

Vision: light is focused by the lens onto the retina; signals travel via the optic nerve. Disorders: myopia (short-sightedness, eye too long), hyperopia (long-sightedness, eye too short), cataracts (lens clouding), glaucoma (optic nerve damage from elevated pressure). Technologies: corrective lenses, LASIK surgery, intraocular lens implants.

Depth of study

Module 8 includes a depth-of-study component your school chooses. Common options:

Epidemiology: statistical analysis of disease patterns (e.g. lung cancer epidemiology).
Prevention: intervention programs (e.g. national HPV vaccination program).
Diagnosis: technologies for detecting disease (e.g. MRI for brain disorders, biopsies for cancer).
Genetic disorders: specific named conditions, their genetic basis, and current management.

Memorise the specifics for your school's chosen depth.

Common HSC Modules 7-8 traps

Conflating innate and adaptive immunity: Innate is non-specific and immediate. Adaptive is specific and develops over days. Memorise the players in each.
Forgetting the feedback loop structure: When asked about homeostasis, name all four components: stimulus, receptor, control centre, effector. Markers reward this structure.
Mixing up Type 1 and Type 2 diabetes: Type 1 = no insulin (autoimmune destruction of beta cells). Type 2 = insulin resistance.

Generic answers about "disease." Markers reward specific named examples. Always cite at least one named pathogen, disease, technology, or treatment in extended responses.

Ignoring evaluation in disease management questions. Many extended responses ask you to compare or evaluate. Pure description scores lower than evaluation that weighs effectiveness, accessibility, ethics, and side effects.

How Modules 7 and 8 are examined

In the HSC Biology exam:

Multiple choice. 6-8 questions across these modules.
Section II short questions (3-5 marks). Identify pathogen types. Describe immune response steps. Trace a feedback loop.
Section II extended response (6-9 marks). Multi-part integrated questions. Common patterns: describe the immune response to a specific pathogen AND evaluate vaccination's role; explain homeostasis in a specific scenario AND link to a disorder when it fails; compare two named disease management strategies.

Practice strategy

For HSC Biology Modules 7 and 8:

Term 2-3 of Year 12. Build the immune response diagram from memory. Master the feedback loop structure.
Term 3. Memorise named examples (at least 20 across the two modules).
Term 4. Past papers, focused on extended responses. Most exam years have a major question on infectious disease OR immunity AND a homeostasis question.

See our HSC Biology practice questions for prompts modelled on NESA past papers.

Check your knowledge

A mix of definitional, calculation/explanation, and exam-style multi-part questions covering this topic. Aim to answer all under exam conditions, then check against the solutions block.

Define antigen and antibody, and explain how their interaction underpins both the adaptive immune response and the principle of vaccination. (3 marks)
Mycobacterium tuberculosis causes tuberculosis (TB), a re-emerging concern in some remote Aboriginal communities in the Northern Territory. (a) Identify the pathogen group. (b) Outline the typical mode of transmission and the portal of entry. (c) Describe two innate-immune and two adaptive-immune responses mounted against this pathogen. (5 marks)
The graph (described in words) shows the antibody titre in blood over time after a hypothetical influenza vaccine: a small peak of about 100 units around day 14 (primary response), declining to 20 units by day 60; a second dose at day 90 produces a rapid peak of 900 units by day 100. (a) Identify which curve represents the primary versus secondary response. (b) Explain the difference in magnitude and timing in terms of memory cells. (c) Predict the response if a person with no prior exposure to influenza were given the second dose only. (5 marks)
(a, 3) Compare innate and adaptive immunity on three points: specificity, timing of response, and memory. (b, 3) Describe the role of helper T cells, cytotoxic T cells and B cells in the coordinated response to a viral infection such as SARS-CoV-2. (c, 2) Discuss one limitation of adaptive immunity that is exploited by influenza viruses. (8 marks)
(a, 2) Define $R_0$ and state the threshold value for an outbreak to be self-sustaining. (b, 3) For measles, $R_0 \approx 15$ . Calculate the herd-immunity threshold using $1 - 1/R_0$ . (c, 3) Compare this with COVID-19 ( $R_0 \approx 3$ for the original strain) and explain why even a 70 percent vaccinated population in Australia did not eliminate community transmission during the 2022 Omicron wave (which had a higher effective $R_0$ ). (8 marks)
A NSW research laboratory tracks insulin and blood-glucose levels in a healthy adult before and after a meal: at $t = 0$ min, glucose = 5.0 mmol L $^{-1}$ , insulin = 60 pmol L $^{-1}$ ; at $t = 30$ min, glucose = 9.5 mmol L $^{-1}$ , insulin = 380 pmol L $^{-1}$ ; at $t = 90$ min, glucose = 6.8 mmol L $^{-1}$ , insulin = 200 pmol L $^{-1}$ ; at $t = 180$ min, glucose = 5.2 mmol L $^{-1}$ , insulin = 70 pmol L $^{-1}$ . (a) Describe the feedback loop responsible. (b) Calculate the percentage change in glucose and in insulin from $t = 0$ to $t = 30$ min. (c) State whether this is positive or negative feedback and predict how the curves would change in a person with untreated Type 2 diabetes. (6 marks)
Compare antibiotic resistance and vaccine evasion as mechanisms by which pathogens escape current control measures. Address (a) the molecular mechanism (gene mutation versus antigenic drift/shift), (b) the rate at which each typically evolves, and (c) an Australian public health response to each. (6 marks)
The HPV vaccine has been administered to NSW students through a school-based program since 2007. (a, 2) Identify the pathogen and the disease it causes. (b, 3) Explain mechanistically how the vaccine produces immunity, including the role of antigen, B cells, and memory cells. (c, 3) Discuss two pieces of epidemiological evidence that the program has been effective. (d, 2) Evaluate one ethical or accessibility consideration of compulsory school-based vaccination programs in a multicultural society. (10 marks)

Solutions

Q1: An antigen is any molecule (typically a protein or polysaccharide) that the immune system recognises as foreign and that triggers a specific immune response. An antibody is a Y-shaped immunoglobulin protein produced by B lymphocytes (plasma cells) that binds specifically to a matching antigen, neutralising the pathogen or marking it for destruction. The specificity of antibody-antigen binding is the basis of adaptive immunity: each B cell produces antibodies targeting one antigenic shape. Vaccination introduces an antigen (weakened pathogen, killed pathogen, subunit, or mRNA encoding the antigen) so that the immune system mounts a primary response, generating memory B and T cells that produce a rapid, large secondary response on subsequent exposure to the real pathogen.
Q2: (a) Bacterium (prokaryote with peptidoglycan cell wall). (b) Transmission is airborne via respiratory droplets and aerosols (a contagious person can produce infectious aerosols on coughing); portal of entry is the lower respiratory tract. (c) Innate: alveolar macrophages phagocytose inhaled bacilli; ciliated epithelium in the airways traps and moves pathogens upward. Adaptive: cytotoxic T cells recognise infected macrophages presenting bacterial antigens on MHC class I and kill them; B cells produce IgG antibodies against mycobacterial surface antigens (although cell-mediated immunity dominates because TB is intracellular). Granuloma formation walls off the infection.
Q3: (a) The day-14 peak of 100 units is the primary response (slow, modest); the day-100 peak of 900 units is the secondary response (rapid, large). (b) During the primary response, naive B cells take 7 to 14 days to recognise antigen, proliferate, and differentiate into plasma cells producing antibodies; the response is modest because the number of antigen-specific cells is small. The primary response also generates long-lived memory B cells. On second exposure, memory B cells respond immediately, proliferate rapidly, and produce an order-of-magnitude larger antibody titre. (c) A naive person given only the "second" dose would mount a primary-like response: slow and modest, peaking around day 14 at about 100 units, with no rapid secondary spike, because no memory cells exist.
Q4: (a) Specificity: innate responses recognise broad pathogen-associated molecular patterns (PAMPs); adaptive responses recognise unique antigens. Timing: innate is immediate (minutes to hours); adaptive develops over days. Memory: innate has no memory; adaptive produces memory cells lasting years to lifetime. (b) On SARS-CoV-2 infection, dendritic cells engulf virus and present spike-protein fragments on MHC class II to helper T cells, activating them. Helper T cells release cytokines that stimulate B cells (which produce anti-spike antibodies) and cytotoxic T cells (which kill infected cells displaying viral antigens on MHC class I). Memory B and T cells persist after infection. (c) Limitation: adaptive immunity is antigen-specific, so antigenic variation defeats it. Influenza A undergoes both antigenic drift (gradual mutation of haemagglutinin and neuraminidase) and antigenic shift (re-assortment of segmented RNA in animal reservoirs producing pandemic strains), requiring annual reformulation of the vaccine.
Q5: (a) $R_0$ (basic reproductive number) is the average number of secondary cases produced by one primary case in a fully susceptible population. An outbreak is self-sustaining when $R_0 > 1$ ; it dies out when $R_0 < 1$ . (b) Herd immunity threshold $H = 1 - 1/R_0 = 1 - 1/15 = 0.933 = 93.3$ percent. (c) For COVID-19 with $R_0 \approx 3$ , $H = 1 - 1/3 = 66.7$ percent. Australia's 2022 vaccination rate of about 70 percent would, in principle, just exceed this for the original strain. However, the Omicron variant had an effective $R_0$ estimated at 8 to 10 due to immune escape and increased transmissibility, raising the herd-immunity threshold to 87 to 90 percent. Vaccine efficacy against transmission was also reduced, the 70 percent figure included partial vaccination, and waning immunity over 6 months further reduced effective protection. Combined, these factors meant community transmission was not eliminated.
Q6: (a) After a meal, blood glucose rises (stimulus); beta cells in pancreatic islets detect this (receptor); they secrete insulin (control centre signal); muscle, liver and adipose cells take up glucose and the liver converts excess glucose to glycogen (effectors); blood glucose returns to baseline. (b) Glucose change: $(9.5 - 5.0)/5.0 \times 100 = +90$ percent. Insulin change: $(380 - 60)/60 \times 100 = +533$ percent. (c) This is negative feedback: the response (insulin secretion) opposes the change (rising glucose) and restores the baseline. In untreated Type 2 diabetes, target cells show insulin resistance: insulin levels rise normally or even higher, but glucose stays elevated for much longer (peak persists past 90 min, slower return toward baseline). With progression, beta-cell exhaustion eventually reduces the insulin peak too.
Q7: (a) Antibiotic resistance arises by mutation (point mutations altering antibiotic targets, plasmid acquisition of resistance genes via horizontal transfer, mutations in efflux pump genes). Vaccine evasion arises by antigenic variation: drift (small mutations in surface antigens) and shift (large recombinations between strains in animal reservoirs, as with influenza). (b) Antibiotic resistance can emerge within years (MRSA in the 1960s) or even months in a hospital under heavy antibiotic use; antigenic drift produces vaccine-evading influenza annually, antigenic shift causes pandemics every 20 to 40 years. (c) Australia's response to antibiotic resistance includes the National Antimicrobial Resistance Strategy (stewardship guidelines for prescribers, surveillance via AGAR). Australia's response to vaccine evasion includes the annual Australian Influenza Vaccination Program (formulated each year to match circulating strains) and continuous surveillance through the National Notifiable Diseases Surveillance System.
Q8: (a) Human papillomavirus (HPV) - a small DNA virus that infects epithelial cells of the cervix and other mucosa. High-risk strains 16 and 18 cause approximately 70 percent of cervical cancers; the quadrivalent and nine-valent vaccines also target genital warts. (b) The HPV vaccine contains virus-like particles (VLPs) of the L1 capsid protein - empty shells with no genetic material, so they are non-infectious. Dendritic cells present L1 epitopes to helper T cells; B cells specific to L1 proliferate and produce anti-L1 antibodies (plasma cells), and a memory B-cell population is established. On subsequent exposure to live HPV, antibodies neutralise the virus before it infects epithelial cells, preventing the persistent infection that progresses to cancer over years to decades. (c) Epidemiological evidence: (i) The 2018 Lancet study and 2023 updated data show a 90 percent reduction in high-grade cervical lesions among vaccinated cohorts in Australia, with cervical cancer incidence projected to fall below 4 per 100,000 by 2028 (the WHO elimination target). (ii) Genital wart prevalence in young women fell from 11.5 percent in 2006 to less than 1 percent by 2015. (d) Ethical/accessibility consideration: school-based vaccination ensures high coverage and equitable access but can conflict with cultural or religious beliefs. Some Australian families decline based on perceived encouragement of sexual activity in young adolescents. Public-health responses include strong communication of vaccine safety, opt-in consent, and culturally tailored outreach in CALD (culturally and linguistically diverse) communities. The program's voluntary nature and parental consent process preserve autonomy while maximising population coverage.

Sources & how we know this

Biology Stage 6 Syllabus (2017) — NESA
Biology HSC exam papers — NESA