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

What the two modules ask

HSC Biology Modules 7 (Infectious Disease) and 8 (Non-infectious Disease and Disorders) together form about 60% of the exam. They are 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.

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.

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:

1. Stimulus (deviation from the set point)
2. Receptor (detects the stimulus)
3. Control centre (processes the signal, often in the brain or via hormones)
4. 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.

In one sentence

HSC Biology Modules 7 and 8 form 60% of the exam 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.