2025 VCE Biology (NHT) external
assessment report
This report provides sample responses, or an indication of what responses may have included. Unless
otherwise stated, these are not intended to be exemplary or complete responses.
Section A – Multiple-choice questions
Question Correct answer
1 D
2 B
3 C
4 A
5 D
6 A
7 D
8 C
9 B
10 B
11 A
12 D
13 B
14 A
15 B
16 A
17 C
18 B
19 C
20 C
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2025 VCE Biology (NHT) external assessment report
Question Correct answer
21 D
22 A
23 C
24 B
25 C
26 A
27 C
28 D
29 B
30 C
31 C
32 B
33 B
34 C
35 B
36 A
37 D
38 B
39 D
40 C
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2025 VCE Biology (NHT) external assessment report
Section B
Question 1a
When E. coli are in an environment with low levels of trp, the repressor protein is inactive OR not bound to
the operator.
When E. coli are in an environment with high levels of trp, two trp amino acids bind to the repressor protein,
changing its shape so it then binds to the operator, blocking RNA polymerase from binding to the promoter to
initiate transcription.
Students were required to refer to the activity of the repressor protein in environments with low and high
levels of trp.
Question 1b
The function of mRNA in the production of proteins includes:
coding for proteins/enzymes involved in the synthesis of trp
carrying a copy of the genetic code to the ribosome for translation OR to be read by tRNA after binding to
the ribosome.
The function of trp in the production of proteins includes:
being an amino acid/monomer for proteins
contributing to the growing polypeptide chain OR overall 3D functional shape of proteins.
Students were required to describe at least one function for both mRNA and trp in the production of proteins.
Question 2a
Similarities between the biochemical pathways of fermentation in human and yeast cells include:
no oxygen is used
both produce ATP/energy
glycolysis occurs OR glucose is converted to pyruvate OR pyruvate is produced
the same enzymes are used in glycolysis.
Differences between the biochemical pathways of fermentation in human and yeast cells include:
different products are produced – lactic acid in humans compared to ethanol and carbon dioxide in yeast
different enzymes are involved in the conversion of pyruvate to final products.
As this was a ‘compare’ question, students could provide similarities and differences or a combination of
both.
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2025 VCE Biology (NHT) external assessment report
Question 2b
The general role of coenzymes in biochemical pathways includes:
assisting enzymes in catalysing reactions OR lowering activation energy
cycling between loaded and unloaded forms
carrying energy (e.g. ATP)
carrying protons/hydrogen (ions) and/or electrons (e.g. NADH, FADH2, NADPH).
Students should be careful not to confuse the role of coenzymes with that of enzymes. Coenzymes do not
catalyse reactions; instead, they assist enzymes in their role as protein catalysts.
Question 3a
The RGA2 gene is incorporated into a bacterial plasmid through:
cutting the plasmid with a specific endonuclease
cutting the RGA2 gene using the same endonuclease used to produce the sticky ends for the plasmid
DNA ligase joining the phosphodiester bonds between the RGA2 gene and the plasmid.
Students could also mention that the RGA2 gene is isolated using a specific endonuclease or that the
overhanging bases / sticky ends form hydrogen bonds between complementary base pairs.
Students should note that DNA ligase joins the phosphodiester bonds between the gene and plasmid, not
hydrogen bonds, which exist between complementary base pairs of the two DNA strands.
Question 3b.i
The TR4-resistant Cavendish bananas are genetically modified, as the RGA2 gene came from the same
species / M. acuminata.
A transgenic organism has had genes from a different species inserted.
Question 3b.ii
Reasons why there are no plans for Australian farmers to grow TR4-resistant Cavendish bananas on a large
scale or sell them to consumers include:
Cavendish bananas not being in short supply OR still growing in Australia, as only nine farms were
infected with the TR4 disease (economic implication)
TR4-resistant plants needing to be labelled as genetically modified (GM) (legal implication)
the cost or time required to upscale research and grow new banana varieties OR the cost to consumers
(economic/political implication)
the education required for farmers/consumers OR the marketing campaigns required for consumers
(social implication)
consumers being deterred by GM labels OR not guaranteed to purchase GM products (social
implication).
Other appropriate reasons were also accepted.
For this type of question, students are encouraged to apply their knowledge and skills of ethical
understanding (see page 12 of the Study Design). Specifically, students should be able to apply the VCE
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2025 VCE Biology (NHT) external assessment report
Biology Units 1–4 key science skill regarding ‘… the influence of social, economic, legal and political factors
relevant to the selected issue’.
Question 4a
A case study is an appropriate methodology for the World Health Organization (WHO) to monitor both animal
and human cases of swine flu around the world because:
it contains a real-world situation / real-world data, which informs health bodies/scientists
analysis of the causes and consequences of current and/or past outbreaks can lead to plausible/timely
recommendations to help manage future outbreaks.
Students could also support their answer to this question by assessing why another methodology may not be
appropriate, including by explaining that:
fieldwork would require the WHO/scientists to have contact with the virus, which would potentially be
unsafe
a controlled experiment may be difficult, as there are many unknown variables OR it may be perceived
as unethical to infect / test on patients
a correlational study is not required, as the WHO already understands the relationships or associations
between animal and human cases of swine flu.
This question proved challenging for students. Therefore, they are encouraged to review the various forms of
scientific investigation methodologies outlined in the Study Design on pages 9–10.
Question 4b
The function of the MHC Class I marker on cells infected with the swine flu virus is that it allows:
the immune system to distinguish the cells’ self-antigens from non-self antigens
infected cells to display swine flu antigens to activate natural killer OR cytotoxic T cells.
Question 4c
The role of dendritic cell A, which has a high amount of MHC Class II markers and low production of
interferons, would be to engulf the pathogen OR present the foreign antigen fragments to helper T cells,
allowing the pathogen to be removed from the body.
The role of dendritic cell B, which has a low amount of MHC Class II markers and high production of
interferons, would be to alert uninfected cells of potential infection to produce defences to the pathogen
before they are infected OR attract other immune cells to the infected area to slow the spread/replication of
the pathogen, allowing a faster recovery.
Question 5a
The roles played by helper T cells in the adaptive immune response include:
activation when presented with antigens of C. burnetiid by an antigen-presenting cell
release of cytokines
formation of memory T helper cells
activation of cytotoxic T cells
activation of B cells.
Students should note that helper T cells do not collect or present the antigen fragments themselves.
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2025 VCE Biology (NHT) external assessment report
Question 5b
Polymerase chain reaction (PCR) is used to amplify the pathogen DNA to identify or analyse it further
through gel electrophoresis.
Students may have also answered this question by referring to the use of primers to anneal to bacterial DNA
OR the use of Taq DNA polymerase to synthesise new bacterial DNA OR heating up DNA to separate DNA
strands so specific regions can be amplified.
Question 5c
Examples of reasons why 90% of Q fever cases are not identified include:
people not being tested
testing early in the onset of disease OR months after the onset of disease when antibody levels are not
high enough to display in the test
a low proportion of the population being infected
a long incubation period, meaning people are not aware they are infected
the expense associated with collecting and analysing blood samples from individuals.
Question 5d
Examples of a strategy that could be implemented by the Australian Government to control the spread of
Q fever include:
isolation OR quarantine of infected individuals
use of existing vaccination
mandatory reporting of cases
education or disinfection protocols for individuals working with animals
prevention of movement of animals OR screening of animals OR culling of infected animals.
Question 5e
Reasons why the National Immunisation Program (NIP) does not provide free vaccination against Q fever,
but does for many other infectious diseases, include:
person-to-person spread is unlikely
a specific population is at risk of infection (those working with animals), so herd immunity is not required
OR vaccination is only effective for those working with animals
the cost to vaccinate everyone is high when the number infected is so low.
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2025 VCE Biology (NHT) external assessment report
Question 6a
Population Prediction Justification
(increase,
decrease, stay the
same)
St Kilda decrease Examples of justifications accepted include:
small gene pool
reduced gene flow
exposed to harsh living conditions so only favourable alleles continued to be
passed on
population arose from a genetic bottleneck
alleles removed from the gene pool as migration to mainland occurred.
Lord Howe increase Examples of justifications accepted include:
Island increased gene flow or introduction of new alleles into the population from different
regions
larger gene pool from favourable environmental conditions.
For this question, one mark was assigned to each correct population prediction for their change in genetic
diversity, and one mark for a correct justification for each predicted change.
Question 6b
The cause of the outbreak was virus particles present on the dead man’s clothing, which was handled by
community members.
Examples of the impact this had on the St Kilda population include:
individuals became infected
the infection spread rapidly in the small island community
individuals lacked immunity or herd immunity against smallpox
the population had a small gene pool OR limited genetic diversity, so smallpox significantly decreased
the population, as most individuals were similarly affected.
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Question 6c
Students were able to use any one of the five bioethical concepts to answer this question. They were
required to include each of the following in their response:
name OR definition of bioethical concept
explanation of how the concept relates to the article/decision
the ethical justification for relocation.
Examples of responses include:
non-maleficence / avoidance of the causations of harm
harsh environmental conditions / poor nutrition / high disease vulnerability was causing significant harm
to the St Kilda population
prevention of further suffering / potential loss of life
justice / moral obligation to ensure there is no unfair burden on a particular group
unsustainable existence of St Kilda population under harsh conditions / unequal access to resources
and/or healthcare compared to mainland population
relocation to mainland, where there is better access to healthcare and/or resources
integrity / honest reporting of information, whether favourable or unfavourable
government informs population about why they are being relocated / provides them with pros and cons
best interests for population / better livelihood / experience less harm
beneficence / commitment to maximising benefits and minimising risks and harms
resources/healthcare available on the mainland
ensuring long-term health and survival of population / population will experience less harm
respect / regard for the welfare, autonomy, beliefs, customs, cultural heritage and so on of the St Kilda
population
population was consulted/informed / evacuation was not imposed
respecting their right to make informed choices about their future / better livelihood
While students could recall the different types of bioethical concepts, as listed in the Study Design on
page 16, many did not clearly relate these concepts to the correct context of the question, which was the
relocation of the human population from St Kilda.
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2025 VCE Biology (NHT) external assessment report
Question 6d
Antigenic shift results in the emergence of a new viral strain OR existing antibodies/memory cells/vaccines
may not recognise the virus antigen.
Some examples of how this could pose a current public health threat on Lord Howe Island include:
the small population could experience a rapid transmission of the virus due to close contact among
residents/visitors
if a tourist became infected before containment, this could lead to an epidemic/pandemic
the limited healthcare infrastructure, due to isolation from the mainland, might create challenges in
receiving vaccines / medical supplies / treatments
if no treatment existed OR current treatment was no longer effective, it would take time to develop
antivirals
the efficacy of current vaccines varies, as some individuals could mount a stronger immune response
than others.
Students were required to make specific reference to the Lord Howe Island context in their response to be
awarded full marks.
Question 7a.i
Hominin cranial capacity / brain size has increased over time.
Students were required to include any two correct data points of comparison, for example, from 678 cm3 in
H. habilis to 1464 cm3 in H. sapiens (300 000 to 129 000 ya).
Question 7a.ii
Examples of advantages of the change in hominin brain size over time include:
more developed regions or folding of the brain / allowed for more complex thinking or problem-solving
more likely to survive and reproduce / communicate / manipulate environment.
Question 7b
Homo sapiens cranial capacity / brain size decreased over time OR is the opposite of the increasing trends
in earlier hominin species.
Students were required to include any two correct data points of comparison, for example, from 1464 cm3 in
H. sapiens (300 000 to 129 000 ya) to 1304 cm3 in H. sapiens (present).
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Question 7c
Some examples of possible recommendations to extend the investigation to improve the study include:
analysing other hominin data (e.g. height) to determine a ratio for comparison that would improve the
validity/accuracy of results
determining if cranial capacity measurements were from adults or children, or had gender differences
that would improve the validity/accuracy of results
determining how cranial capacities were measured to remove outliers
considering other ways of taking measurements to remove systematic or random errors, improving
accuracy or precision, respectively
collecting more data from modern humans to improve the validity of results.
Students were required to connect their answers to a correct Biology Unit 1–4 key science skill. Students
should be familiar with the ‘Key science skills’ and ‘Data and measurement’ sections in the Study Design on
pages 7–8 and 14–15, respectively.
Question 8a
Examples of the useful information scientists were able to determine about the plants of vegetable crops by
measuring the reflected light wavelengths include:
wavelength(s) of light absorbed for photosynthesis / favourable for growth of the plant
amount of light absorbed by the plant
amount or type of chlorophyll
health of the plant
if the crop is being produced or flowering / not flowering.
Students should understand that the wavelengths of light that are reflected are not as well absorbed by the
plant. Therefore, responses could link to the light-dependent stage of photosynthesis or pigments (such as
chlorophyll) involved in light absorption.
Question 8b
Examples of two pieces of data, other than reflected wavelength, that the scientists collected to determine
vegetable crop suitability include:
biomass
size / plant height
leaf characteristics
heat resistance OR flooding
growth rate
variable crop yield
overall plant health.
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Question 8c
Examples of two advantages of the scanner over data collection by fieldworkers include:
reduced labour OR a smaller team managing plant care / harvest
easier / more accurate identification of plant varieties that could be grown in certain environments
increased data / traits of plants collected
easier identification of desired traits so farmers can produce more crops or improve their livelihood
faster collection of data, improving the accuracy/quality of data.
Student responses were required to focus specifically on the advantages of the scanner, compared to
fieldworkers, in terms of data collection.
Question 8d
Similarities between the photosynthetic pathways in C3 and CAM plants include:
Rubisco fixes carbon dioxide in the Calvin cycle
photosynthesis occurs in the same cell type (mesophyll cells)
the light-dependent stage is identical OR it occurs before the light-independent stage.
Differences between the photosynthetic pathways in C3 and CAM plants include:
in CAM plants, a different enzyme (PEP carboxylase) fixes carbon dioxide first
CAM plants have two stages of carbon fixation, whereas C3 plants only have one stage of carbon
fixation
CAM plants fix carbon dioxide at night, whereas C3 plants fix carbon dioxide during the day
in CAM plants, carbon dioxide is stored in a C4 compound (malate), whereas C3 plants use carbon
dioxide immediately
in CAM plants, the stomata are typically closed during the day, whereas stomata in C3 plants are usually
open during the day.
The adaptations in CAM plants that enable them to survive in hot, arid environments include:
minimising photorespiration at high temperatures
closing stomata during the day to reduce water loss.
Since this was a ‘compare’ question, as part of their response students were required to compare the
photosynthetic pathways by providing at least two differences between the C3 and CAM plants. This meant
they could also compare the two types of plants by providing one or more similarities between them.
Responses then needed to explain either one or two of the adaptations in CAM plants that assist them to
survive.
Question 9a
Blackbutt / E. pilularis is the tree species most effective at capturing carbon dioxide.
Examples of justifications for this include:
the Blackbutt showed the highest predicted biomass compared to other species
as its trunk diameter increased, biomass also increased
it fixed/stored more carbon dioxide, resulting in more photosynthesis
appropriate use of data from the graph (e.g. at a trunk diameter of 50 cm, Blackbutt’s predicted biomass
was approximately 1900 kg).
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Question 9b
Examples of limitations of the method used by students include:
only using the diameter to provide information about the tree’s trunk
no data was collected about the overall height or shape of tree / root mass / number of leaves/branches,
etc.
it assumes the tree trunk is circular OR there may have been irregularities in the trunk shape
a limited number of species for comparison of predicted biomass
no indication of repeatability OR how many trees should be measured
no indication of how the tree was identified for reproducibility.
Question 9c
Examples of safety precautions that should be followed by the students include:
avoid tripping hazards or uneven ground
wear protective clothing (e.g. gloves, boots, hard hat)
avoid standing under large branches that could fall.
Examples of ethical guidelines that should be followed by the students include:
no material should be removed during measurements
living organisms OR the ecosystem should not be disturbed or damaged OR should be respected
approval must be granted by the park/forest to conduct fieldwork.
Students could provide two different examples of safety precautions, two different examples of ethical
guidelines, or a combination of one safety precaution and one ethical guideline that should be followed.
Question 9d
CRISPR-Cas9 technology could improve the efficiency of photosynthesis through either:
altering the gene for chlorophyll production so a greater rate of photosynthesis / light absorption occurs
altering the gene for an enzyme (e.g. Rubisco) so more photosynthesis / a light-independent stage
occurs OR less photorespiration occurs.
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