TCE Biology (BIO315124) deep dive: criteria 3, 5, 6, 7 and 8 for the 2026 exam

How this deep dive is organised

The TASC Biology exam gives one rating for each of criteria 3, 5, 6, 7 and 8, and TASC's exemplar paper has one section per criterion. This guide follows that structure and the content listed in the BIO315124 course document. Each section links the matching dot-point pages, and the TCE Biology hub maps every page to its module and criterion. For the exam format and award rules, see the exam strategy guide.

Criterion 3: biological inquiry

Dot point: designing and evaluating biological investigations.

Every investigation answer should cover:

• a testable hypothesis linking the independent and dependent variables;
• the independent variable and its values, and the dependent variable with exactly how it is measured;
• controlled variables relevant to the organism or reaction;
• a control where appropriate, and repeat trials;
• data processing: means, rates, percentage change, and a graph with a title, labelled axes and units;
• evaluation: sources of error, their effect on the data, and specific improvements.

Criterion 5: regulation of cells and systems

Dot points: enzymes, photosynthesis, cellular respiration, DNA structure and replication, protein synthesis, the lac operon, mutations, biotechnology.

Enzymes are globular proteins with an active site. Temperature, pH, enzyme and substrate concentration, inhibitors, and coenzymes and cofactors all affect the rate.

Photosynthesis (chloroplasts) and respiration (mitochondria for the aerobic stages) are required as balanced net equations:

Know the stages by name (light and light-independent reactions; glycolysis, the Krebs cycle and the electron transport chain) and the factors affecting each rate.

DNA replication uses helicase (unwinds and separates strands), primase (adds a primer), DNA polymerase (adds complementary nucleotides) and ligase (joins fragments); it is semi-conservative. Protein synthesis is transcription of a gene to mRNA in the nucleus, then translation at the ribosome using tRNA anticodons. In prokaryotes, the lac operon switches lactose-digesting genes on only when lactose is present.

Mutations include substitutions, deletions, additions and inversions, plus chromosomal changes during cell division, and can be caused by UV and ionising radiation, heat and chemicals. A deletion or addition in a coding region shifts the reading frame; a substitution may change one amino acid or none.

Criterion 6: homeostasis

Dot points: negative feedback, nerve impulses, hormones, thermoregulation, glucose regulation, osmoregulation, transpiration, arid environments.

Homeostasis uses a stimulus-response model with negative feedback. Receptors and effectors are linked by a control centre through nervous pathways, hormonal pathways, or both.

• Nerve impulses travel as action potentials along axons; at synapses, neurotransmitters carry the signal across the gap.
• Hormones from endocrine glands travel in the blood to target cells and increase or decrease their activity.

Plants move water from roots to leaves through the xylem by root pressure, cohesion and transpiration. Transpiration increases with light intensity, temperature and wind, and decreases with humidity. Xerophytes (and desert animals) survive arid conditions through structural features (thick waxy cuticles, sunken stomata, reduced leaves), behaviour (nocturnal activity, burrowing) and physiology (concentrated urine, stomata that close in the heat).

Criterion 7: pathogens and the immune response

Dot points: pathogens and transmission, innate immune response, adaptive immune response, active and passive immunity.

• Pathogens: prions, viruses, bacteria, fungi, protists and parasites, transmitted by direct contact, body fluids, contaminated food or water, or vectors.
• First line (innate): physical and chemical barriers such as skin, mucus and stomach acid.
• Second line (innate): inflammation, fever and phagocytes (neutrophils and macrophages), with mast cells releasing histamine.
• Third line (adaptive): antigen-presenting cells (dendritic cells, macrophages) activate helper T cells; B lymphocytes produce antibodies (humoral immunity); cytotoxic T cells destroy infected cells (cell-mediated immunity); regulatory T cells switch the response down; memory B and T cells give long-term immunity.

Criterion 8: cell division, genetics and evolution

Dot points: cell division: mitosis and meiosis, inheritance and variation, natural selection and adaptation, population genetics, speciation, pedigree analysis.

• Cell cycle: G1, S (DNA replication), G2, M (prophase, metaphase, anaphase, telophase) and cytokinesis.
• Meiosis creates variation through crossing over between non-sister chromatids of homologous chromosomes and independent assortment; random fertilisation adds more.
• Inheritance patterns to model with Punnett squares: autosomal dominant and recessive, sex-linked dominant and recessive, incomplete dominance, codominance, and ABO blood groups ($I^A$, $I^B$, $i$). Use pedigrees to identify the pattern.

Evolution: mutation is the ultimate source of new alleles; natural selection, gene flow and genetic drift change allele frequencies. Geographically isolated populations under different selection pressures can diverge into new species. Bottlenecks reduce genetic diversity and raise extinction risk; Tasmanian devils, for example, have low genetic diversity, which is thought to have left them more vulnerable to devil facial tumour disease.

Common mistakes

Check your knowledge

1. Which enzyme joins DNA fragments? (Answer: ligase.)
2. Which hormone increases water reabsorption in the collecting duct? (Answer: ADH.)
3. Which immune cells make antibodies? (Answer: plasma cells derived from B lymphocytes.)

Then try the criteria quiz.