HSC Biology: what actually gets examined

Better responses

• Building Punnett squares with a key, turning the resulting genotypes into a ratio of phenotypes and expressing any probability in one consistent form.
• Explaining variation through what meiosis actually does, such as allele exchange during crossing over, and connecting that variation to a population's survival.
• Setting out polypeptide synthesis in order: transcription with uracil pairing to adenine, tRNA anticodons matching mRNA codons and carrying specific amino acids, then folding.
• Pointing to named individuals on a pedigree and their possible genotypes when justifying an inheritance pattern or a particular genotype.
• Comparing reproductive strategies with specific organisms rather than broad groups, and drawing the similarities and differences from the data supplied.

Where marks were lost — and how to keep them

• Keeping DNA replication separate from transcription and translation, while knowing which features the two processes share when a comparison is asked for.
• Choosing allele letters whose upper and lower cases look clearly different, and naming the inheritance pattern precisely, such as autosomal recessive rather than recessive.
• Recognising that external fertilisation is still sexual reproduction, and that self-pollination involves gametes so is not asexual.
• Telling chromosomes from chromatids, drawing the gametes that meiosis produces, and comparing mitosis and meiosis by their features rather than by their outcomes.
• Reading a codon chart against the mRNA sequence given, without transcribing it again first, and remembering that several codons can specify one amino acid.

Better responses

• Following a mutation through each stage: an altered base sequence changes the amino acid sequence, which changes the protein's shape and therefore its function.
• Naming the specific technique, whether recombinant DNA or somatic cell nuclear transfer, and describing every step in sequence with terms like restriction enzyme, ligase, vector and micro-injection.
• Explaining changes in a gene pool with the right terms, genetic drift or bottleneck and gene flow, in cause-and-effect statements tied to the figures in the stimulus.
• Reaching a judgement about a biotechnology's effect on biodiversity or on society that draws on the examples in the table or graph provided and addresses ethical concerns.
• Distinguishing germline from somatic mutations and explaining why only a change in gamete or germline DNA is passed to offspring.

Where marks were lost — and how to keep them

• Separating gene flow from genetic drift, and seeing that gene flow acts on the gene pool while population size governs how far allele frequencies swing.
• Keeping how a transgenic organism is made distinct from selective breeding or cloning, and keeping artificial insemination distinct from IVF.
• Linking a biotechnology to its consequences for biodiversity or for sections of society, rather than stopping at its effect on the individual organism.
• Working out exactly which codons and amino acids a substitution or deletion alters, allowing for codon redundancy, and then sequencing the synthesis steps correctly.
• Using the vocabulary of gene insertion and transformation rather than everyday phrasing, and naming a real technology instead of referring to biotechnology in general.

Better responses

• Sequencing the adaptive response cell by cell: antigen presentation, helper T cells, plasma B cells making antibodies, and memory cells formed for a later exposure.
• Classifying pathogens on concrete features, such as cellular or non-cellular and nucleus present or absent, and outlining a procedure with the result expected for each group.
• Designing a microbial investigation properly: inoculating agar with a pure culture, comparing against a control, repeating trials and building in safety at every step.
• Quoting specific values, averages or years from disease data and explaining each trend through a mechanism, such as heat killing microbes or boosters extending immunity.
• Explaining how a named barrier or pathogen adaptation actually works to block infection or to move the pathogen between hosts, not simply naming it.

Where marks were lost — and how to keep them

• Outlining the full route by which a pathogen travels from one host to another, and proposing control procedures that fit the scenario rather than generic ones.
• Stating controlled variables with enough detail to be meaningful, and keeping reliability, validity and accuracy apart when justifying a design choice.
• Using precise immunology terms such as engulf and antigen, and explaining how memory cells arise in the primary response and act in the secondary.
• Separating the antibody-mediated response from the cell-mediated response, and showing how the innate and adaptive lines of defence work together.
• Committing to a definite judgement about a vaccination schedule, backed by the numbers as well as the written stimulus, rather than describing what the graph shows.

Better responses

• Assessing an epidemiological study through its design features, such as a valid control group and sample, and tying each feature to reliability or validity.
• Graphing with the stimulus headings and units on the axes, a sensible scale, a balanced line of best fit, and the extrapolated line drawn on the graph when a value is read from it.
• Connecting a structural change in the eye or ear to the loss of function it causes, then explaining how a named technology such as a cochlear implant or LASIK restores it.
• Explaining how an education campaign changed public behaviour and so lowered incidence, with a definite judgement drawn from both the text and the graph.
• Describing thermoregulatory and water-balance mechanisms as cause and effect, and classifying adaptations correctly as physiological, behavioural or structural.

Where marks were lost — and how to keep them

• Describing a trend with detail about how the rate of change itself changes, backed by numbers from the graph, rather than noting that both variables rise together.
• Avoiding dot-to-dot lines and extrapolation back to zero, choosing a graph type suited to continuous data, and showing the working for percentage calculations.
• Telling a cochlear implant apart from a hearing aid or a bone-conduction device, and showing how a visual technology bends light to correct vision instead of comparing cost or recovery time.
• Giving a genuine cause rather than a symptom or a category label when explaining a disease from environmental exposure or a chromosomal disorder.
• Explaining how and why an adaptation works for the organism described, and recognising that an individual cannot adapt on the spot when its environment changes.