Biology 2025 HSC exam pack

Students should:

• read the question carefully to ensure that they do not miss important components of the question
• have a clear understanding of key words in the question and recognise the intent of the question and its requirements
• plan the response to assist in the logical sequencing of information
• integrate relevant scientific terms into their responses
• engage with any stimulus material provided and refer to it in their response
• show all working in calculations and include correct units
• present a logical and succinct response that addresses the question
• review their response to ensure that it addresses the question requirements.

Question 21

In better responses, students were able to:

• clearly identify how the named component prevents infection from occurring
• use the stimulus provided to develop their response.

Areas for students to improve include:

• elaborating on how the named component prevents infection from occurring, for example, nasal hairs trap pathogens inhaled in the air
• use components from the stimulus in their response.

Question 22

In better responses, students were able to:

• provide relevant detail on the process with links to the outcome. For example, a bud produced by fungi results in a genetically identical organism when it breaks off the parent (a)
• outline a specific adaptation (b)
• link the adaptation to its role in facilitating transmission between hosts instead of within the host. For example, cholera bacteria produce a toxin that causes watery diarrhoea which flushes contaminated bacteria into the environment through contaminated water sources with poor sanitation, increasing the likelihood of transmission to hosts who consume the water (b).

Areas for students to improve include:

• providing details on the process used for reproduction (a)
• understanding the adaptations of pathogens that increase their transmission, rather than an adaptation that benefits pathogens internally in a host (b).

Question 23

In better responses, students were able to:

• understand the requirements of writing a comparison and have a clear and correct similarity and difference between artificial pollination and artificial insemination
• use headings in a table or explicit terminology to indicate the similarity and difference.

Areas for students to improve include:

• comparing the two processes, rather than listing a separate description of each process
• understanding artificial insemination and not outlining the process of IVF
• if constructing a table, using appropriate headings to distinguish between categories or similarities and differences, rather than just listing information.

Question 24

In better responses, students were able to:

• identify mechanisms for increasing and decreasing body temperature (a).

Areas for students to improve include:

• interpreting the thermoregulation flow chart
• linking the action of mechanism B to heat generation (b).

Question 25

In better responses, students were able to:

• make a correct, definite judgement using the information provided
• identify the data trend in the graph and relate it to the product statement.

Areas for students to improve include:

• relating the Cancer Council suggestion and product information to the graph
• providing an evidence-based judgement.

Question 26

In better responses, students were able to:

• provide both similarities and differences between LASIK and a relevant technology
• demonstrate thorough understanding of a specific visual disorder and clearly explain how a selected technology could treat the disorder.

Areas for students to improve include:

• interpreting the question and the stimulus provided to focus on technology in relation to treatment, rather than just the general comparison in terms of cost, accessibility, healing time
• understanding how technologies can be used to refract light so that vision can be improved
• providing information on technologies beyond the stimulus.

Question 27

In better responses, students were able to:

• use the stimulus data effectively to support the key features of internal and external fertilisation
• provide both similarities and differences between internal and external fertilisation.

Areas for students to improve include:

• differentiating between external fertilisation and asexual reproduction
• differentiating between fertilisation and parental care.

Question 28

In better responses, students were able to:

• clearly reference the roles of X, Y and Z by labelling on the flowchart or identifying explicitly in their response (a)
• demonstrate their understanding of the interaction of components of the adaptive immune response to produce antibodies (a)
• describe features of both variables for primary and secondary exposures (b)
• explain how memory cells are created during primary exposure and clearly link this to the role of these cells upon further exposure to the same pathogen (c).

Areas for students to improve include:

• understanding the interaction between the different cells involved in antibody-mediated immunity and the progression from antigen presentation to antibody production (a)
• applying their knowledge of the adaptive immune response to an unfamiliar situation to correctly describe the key processes in the flowchart (a)
• incorporating a relevant interpretation of the stimulus linked to the question, rather than rewriting the stimulus material (a)
• interpreting the graph to describe specific, distinct features shown in the data, ensuring each feature relates directly to what is displayed rather than relying on broad generalisations or trends from a single variable (b)
• understanding how memory cells are created and their subsequent role in the immune response (c).

Question 29

In better responses, students were able to:

• identify that the components of infectious diseases are caused by a pathogen and can be transmitted between organisms (a)
• provide links between the procedures and how it stops the spread to the rest of the population (b).

Areas for students to improve include:

• providing additional information beyond what was given in the stimulus (b)
• providing procedures that were applicable to the stimulus and not generic (b).

Question 30

In better responses, students were able to:

• recognise that producing transgenic mosquitoes required modification of germline cells so the trait is passed to future generations (a)
• outline all steps involved in recombinant DNA technology. For example, identifying and isolating the SERPINE1 gene using restriction enzymes, inserting the gene into a plasmid vector with DNA ligase, amplifying the recombinant plasmid in bacteria, and transferring the gene of interest into mosquito germline cells via micro-injection or viral vectors so mosquitoes express PAI-1 (a)
• use precise terminology to explain the production of genetically modified organisms, for example, restriction enzymes, ligase, plasmid vector and micro-injection (a)
• name specific genetic technologies. For example, recombinant DNA for insulin production or genetically modified crops such as BT cotton (b)
• provide a consistent, explicit judgement about the impacts of genetic technologies to society (b).

Areas for students to improve include:

• recognising that the question requires describing the production of a transgenic organism, not breeding or cloning mosquitoes (a)
• using terminology that specifically relates to gene insertion and transformation. For example, refer to micro-injection, rather than non-scientific terminology such as ‘place into mosquito’ (a)
• outlining the full sequence of steps, including isolating the gene of interest, inserting it into a vector and transforming mosquito germline cells (a)
• maintaining a clear and consistent judgement throughout the response (b)
• naming specific genetic technologies, rather than referring to biotechnology generally (b)
• identifying broader societal impacts beyond an individual. For example, including environmental, ethical, healthcare and economic considerations (b).

Question 31

In better responses, students were able to:

• support their response with clear and explicit reference to the pedigree, identifying specific individuals to support their justification (a)
• provide a clear and logical process from the template strand to the corresponding amino acid chain (b).

Areas for students to improve include:

• identifying the correct alleles for each individual (a)
• drawing correct Punnett squares for specific individuals which support their justification (a)
• using the correct biological terms, for example autosomal recessive instead of recessive (a)
• selecting appropriate letters to represent dominant and recessive alleles clearly, for example the capital and lower case are different so that they are easily distinguishable like Tt, rather than Ss (a)
• using a codon chart (or similar) to identify amino acids from an mRNA sequence (b).

Question 32

In better responses, students were able to:

• demonstrate a clear understanding of key features of epidemiological studies
• engage appropriately with the stimulus provided
• justify each of the design features to reliability and validity.

Areas for students to improve include:

• using the stimulus to clearly support their chosen design features
• understanding how reliability and validity affect the quality of epidemiological studies.

Question 33

In better responses, students were able to:

• provide similarities and/or differences between the processes of mitosis and meiosis (a)
• interpret the stimulus accurately (b)
• link somatic and germ line mutations to the impact on U, V, W and X (c).

Areas for students to improve include:

• comparing characteristics of the cell division process, rather than the outcomes (a)
• analysing flow diagrams with reference to a key (b).

Question 34

In better responses, students were able to:

• identify that the lack of genetic variation within the smaller gene pool led to increased fluctuations in allele frequency (a)
• provide a clear comparison and judgement on the impact of gene flow on both the small and large populations (b).

Areas for students to improve include:

• understanding that the initial gene flow of four alleles was the same in both populations
• understanding that gene flow affects the gene pool, not vice versa
• explaining how the size of the population influences the rate and impact of gene flow on allele frequency changes.