VCAA Biology How do organisms respond to pathogens?
15 sample questions with marking guides and sample answers
Phytophthora is a pathogen that infects
Australian native plants only.
Australian native animals only.
a broad range of plants.
a broad range of animals.
Reveal Answer
Australian native plants only.
While Phytophthora is a major threat to many Australian native plants, it is not restricted to them and infects plants worldwide.
Australian native animals only.
Phytophthora is a plant pathogen (a type of water mold) and does not infect animals.
a broad range of plants.
Phytophthora is a genus of destructive water molds that are known to infect a wide variety of plant species globally, causing diseases like root rot and potato blight.
a broad range of animals.
Phytophthora specifically targets and infects plants, not animals.
A key component of cell-mediated immunity is the body’s production of
antigens.
antibodies.
memory B cells.
killer T cells.
Reveal Answer
antigens.
Antigens are typically foreign substances (like viral or bacterial proteins) that trigger an immune response, rather than a defensive component produced by the body.
antibodies.
Antibodies are the primary component of humoral immunity, not cell-mediated immunity, and are produced by B cells to target extracellular pathogens.
memory B cells.
Memory B cells are part of the humoral immune response, which relies on the production of antibodies rather than direct cell-to-cell combat.
killer T cells.
Killer T cells (cytotoxic T cells) are a central component of cell-mediated immunity, functioning by directly attacking and destroying infected or cancerous cells.
The transmission of malaria is likely to be reduced by
drought.
floods.
global air travel.
a warm climate.
Reveal Answer
drought.
Drought reduces the availability of stagnant water, which is essential for mosquitoes to breed, thereby decreasing the transmission of malaria.
floods.
Floods often leave behind pools of stagnant water as they recede, creating ideal breeding grounds for mosquitoes and potentially increasing malaria transmission.
global air travel.
Global air travel facilitates the spread of malaria to new regions or its reintroduction to areas where it was previously eradicated, increasing transmission.
a warm climate.
A warm climate accelerates both the mosquito life cycle and the development of the malaria parasite within the mosquito, which increases transmission rates.
Antibiotics are ineffective against viruses because viruses
keep changing their external protein coat.
are able to disguise themselves in the host cell membrane.
are not living cells and thus do not metabolise.
can change antibiotics into useful food substances.
Reveal Answer
keep changing their external protein coat.
While some viruses mutate and change their surface proteins to evade the immune system, this is not why antibiotics fail. Antibiotics target specific cellular machinery, which viruses lack entirely.
are able to disguise themselves in the host cell membrane.
Although some viruses are enveloped in host cell membranes, this is not the reason antibiotics are ineffective. Antibiotics fail because they target bacterial structures, not because the virus is disguised.
are not living cells and thus do not metabolise.
Antibiotics work by disrupting active cellular processes like cell wall synthesis or metabolism. Since viruses are non-living and lack their own metabolic machinery, antibiotics have nothing to target.
can change antibiotics into useful food substances.
Viruses do not consume food or possess metabolic enzymes. While some resistant bacteria can degrade antibiotics, viruses are completely incapable of metabolizing them.
The statements below relate to cells found in the immune system called lymphocytes.
I. matured in bone marrow
II. produces antibodies
III. matured in thymus gland
IV. release cytokines
V. produce memory cells
Which statements relate specifically to T lymphocytes?
III, IV and V
I, II and IV
II, III and V
I, IV and V
Reveal Answer
III, IV and V
T lymphocytes mature in the thymus gland (III), release cytokines to activate other immune cells (IV), and produce memory T cells for long-term immunity (V).
I, II and IV
Statements I (matured in bone marrow) and II (produces antibodies) describe B lymphocytes, not T lymphocytes.
II, III and V
Statement II (produces antibodies) is a characteristic of B lymphocytes, which differentiate into antibody-producing plasma cells.
I, IV and V
Statement I (matured in bone marrow) applies to B lymphocytes, whereas T lymphocytes mature in the thymus gland.
Bevacizumab is a humanised monoclonal antibody that is used to treat several different cancers. Humanising involves removing part of the constant region of a mouse monoclonal antibody and replacing it with the constant region from a human antibody. Therefore the humanised antibody has both human-derived and mouse-derived components.
An advantage of humanising monoclonal antibodies such as bevacizumab would be to
decrease the binding strength between bevacizumab and the cancer cell antigens.
reduce the chances of an immune response against bevacizumab.
allow greater destruction of cancerous and non-cancerous cells.
deliver toxic substances less effectively to the cancer cells.
Reveal Answer
decrease the binding strength between bevacizumab and the cancer cell antigens.
The goal of humanising an antibody is not to decrease its binding strength, as strong binding to the target antigen is necessary for its therapeutic effect.
reduce the chances of an immune response against bevacizumab.
By replacing mouse components with human components, the antibody appears less 'foreign' to the patient's immune system, significantly reducing the risk of an adverse immune response against the treatment.
allow greater destruction of cancerous and non-cancerous cells.
Monoclonal antibodies are designed to specifically target cancer cells, so increasing the destruction of non-cancerous cells would be a harmful side effect, not an advantage.
deliver toxic substances less effectively to the cancer cells.
Delivering toxic substances less effectively would reduce the efficacy of the treatment, which is a disadvantage rather than an advantage.
The complement system is a group of proteins that
enhance the inflammatory response by attracting phagocytes to the site of infection.
remain activated within the circulatory system, ready to encounter foreign antigens.
are activated by helper T cells to create a series of events leading to cell death.
act as allergens, causing the release of histamine.
Reveal Answer
enhance the inflammatory response by attracting phagocytes to the site of infection.
The complement system consists of proteins that, when activated, enhance the immune response by promoting inflammation, attracting phagocytes, and directly destroying pathogens.
remain activated within the circulatory system, ready to encounter foreign antigens.
Complement proteins circulate in the blood in an inactive state and must be triggered by specific pathways (such as the presence of pathogens or antibodies) to become activated.
are activated by helper T cells to create a series of events leading to cell death.
The complement system is primarily part of the innate immune system and is activated by antibodies or pathogen surfaces, not by helper T cells.
act as allergens, causing the release of histamine.
While some complement byproducts can trigger histamine release to promote inflammation, complement proteins are endogenous immune components, not foreign allergens.
Some human cells produce proteins called cytokines.
A major function of cytokines is
signalling immune cells in inflammatory responses.
stimulating B cells to directly attack virally infected cells.
diffusing across a synaptic gap to stimulate the adjacent cell.
communicating very rapidly with a cell that is distant from the cytokine-producing cell.
Reveal Answer
signalling immune cells in inflammatory responses.
Cytokines are essential signaling proteins in the immune system that mediate and regulate immunity, inflammation, and hematopoiesis.
stimulating B cells to directly attack virally infected cells.
B cells produce antibodies to neutralize pathogens rather than directly attacking infected cells; direct destruction of virally infected cells is the function of cytotoxic T cells.
diffusing across a synaptic gap to stimulate the adjacent cell.
Diffusing across a synaptic gap is the specific function of neurotransmitters in the nervous system, not cytokines.
communicating very rapidly with a cell that is distant from the cytokine-producing cell.
Rapid communication with distant cells is characteristic of the nervous and endocrine systems. Cytokines typically act locally and more slowly via autocrine or paracrine signaling.
Malaria can be spread when a mosquito carrying the parasite bites a non-infected person. This is an example of
transmission by direct contact.
vector transmission.
infection by droplets.
airborne transmission.
Reveal Answer
transmission by direct contact.
Direct contact transmission requires physical contact between an infected person and a susceptible person, not an intermediate organism like a mosquito.
vector transmission.
Vector transmission occurs when a living organism, such as a mosquito or tick, carries and transmits an infectious pathogen to another living organism.
infection by droplets.
Droplet transmission occurs when respiratory droplets from coughing or sneezing carry pathogens directly to a susceptible person, which does not involve a mosquito.
airborne transmission.
Airborne transmission involves pathogens traveling through the air over time and distance, rather than being delivered by a biting insect.
Hay fever (allergic rhinitis) is caused by a range of allergens, including pollen, animal fur, dust mites and moulds entering the body via the eyes, nose or mouth.
The cells that release histamine in the allergic response are
mast cells.
eosinophils.
macrophages.
natural killer cells.
Reveal Answer
mast cells.
Mast cells are tissue-resident immune cells that store and release histamine when IgE antibodies on their surface bind to an allergen, triggering the allergic response.
eosinophils.
While eosinophils are involved in allergic reactions and parasitic infections, they primarily release toxic granule proteins and other inflammatory mediators rather than being the main source of histamine.
macrophages.
Macrophages are phagocytic cells responsible for engulfing and digesting pathogens and cellular debris; they do not release histamine.
natural killer cells.
Natural killer cells are cytotoxic lymphocytes that identify and destroy virus-infected or cancerous cells, not cells that release histamine during an allergic response.
The role of the lymphatic system in an immune response includes
carrying mast cells to the site of infection.
activation of platelets to help heal wounds.
transport of antigen-presenting cells, including dendritic cells.
delivery of injected monoclonal antibodies to specific target cells.
Reveal Answer
carrying mast cells to the site of infection.
Mast cells reside in connective tissues and mucous membranes, so they are already present at infection sites rather than being transported there by the lymphatic system.
activation of platelets to help heal wounds.
Platelets circulate in the blood and are part of the cardiovascular system's clotting cascade, not the lymphatic system.
transport of antigen-presenting cells, including dendritic cells.
Lymphatic vessels act as a highway to transport antigen-presenting cells, such as dendritic cells, from infected tissues to lymph nodes to activate T cells.
delivery of injected monoclonal antibodies to specific target cells.
Injected monoclonal antibodies are primarily distributed throughout the body via the bloodstream, not the lymphatic system.
Hendra virus is a disease that can affect horses and human beings. Available evidence implicates fruit bats as the natural reservoir of the Hendra virus, which is transmitted in bodily fluids.
One practical way of controlling the spread of the Hendra virus to horses is to
stop horses from eating fruit.
cover the feed and water containers for horses.
inject all fruit bats with a vaccine against the virus.
minimise the number of fruit trees that bats rely on for food.
Reveal Answer
stop horses from eating fruit.
Horses do not typically eat fruit as a primary food source. The virus is transmitted through bat bodily fluids, which are more likely to contaminate exposed feed and water rather than just fruit.
cover the feed and water containers for horses.
Covering feed and water containers is a highly practical and effective method to prevent contamination from the bodily fluids (such as urine or saliva) of infected fruit bats roosting or flying overhead.
inject all fruit bats with a vaccine against the virus.
Capturing and vaccinating an entire wild population of fruit bats is logistically impossible and therefore not a practical solution.
minimise the number of fruit trees that bats rely on for food.
Destroying the food source of fruit bats would cause severe ecological damage and could actually force bats to relocate closer to human and horse populations in search of food.
During the 2024 Olympic Games in Paris, the cleanliness of the River Seine was of concern. High levels of the bacteria Escherichia coli (E. coli) were detected in the river, presenting potential health risks for the athletes competing in the triathlon and open-water swimming events. Several athletes were treated for E. coli infections.
Contrast three features of bacteria and viruses.
Reveal Answer
Answers could include:
- Bacteria are unicellular and living, whereas viruses are non-living.
- Most bacteria are non-pathogenic, but all viruses are pathogenic.
- Bacteria contain DNA or DNA plasmids, whereas viruses contain DNA or RNA.
- Furthermore, bacteria are surrounded by a cell membrane or cell wall, whereas viruses are surrounded by a protein coat.
- Bacteria replicate independently, while viruses replicate within a host cell.
- Finally, bacteria are visible under a light microscope, whereas viruses are too small to be seen under a light microscope.
| Descriptor | Marks |
|---|---|
Any 3 of the following (2 marks each)
| 6 |
In addition to severe nausea, the unwell swimmers started feeling cold, shivering uncontrollably and were asking for blankets, despite the outside temperatures being warm.
Name and outline the physiological responses the swimmers' bodies were having to the infection.
Reveal Answer
The physiological response is a fever.
During a fever, pyrogens are released, and the hypothalamus resets the internal thermostat to a higher temperature. This causes shivering of skeletal muscles and vasoconstriction of peripheral blood vessels, so body temperature will increase. This helps to inhibit the growth or reproduction of pathogens, and macrophage activity is enhanced, which increases phagocytosis. Eventually the fever will break at the crisis point, causing sweating and vasodilation of peripheral blood vessels as the thermostat is reset to normal.
Name of physiological response
| Descriptor | Marks |
|---|---|
Identifies the physiological response as a fever | 1 |
Outline the physiological response
| Descriptor | Marks |
|---|---|
1 mark for each correct point (any 9 of): States that pyrogens are released; Describes that the hypothalamus resets the internal thermostat to a higher temperature; Identifies shivering of skeletal muscles; Identifies vasoconstriction of peripheral blood vessels; States that body temperature will increase; Explains that this inhibits the growth/reproduction of pathogens; Explains that macrophage activity is enhanced/increases phagocytosis; States that eventually the fever will break/reach a crisis point; Identifies that this causes sweating; Identifies vasodilation of peripheral blood vessels; States that the thermostat is reset to normal | 9 |
After swimming in the River Seine, Australian athletes were prescribed antibiotics to prevent an E. coli infection.
Antibiotics can be classified into two groups based on their mode of action. Name these two groups and outline how they fight bacterial infections.
Reveal Answer
Bactericidal antibiotics kill bacteria by changing the structure of the cell wall or cell membrane, or by disrupting an essential enzyme.
Bacteriostatic antibiotics inhibit growth or prevent reproduction by disrupting protein synthesis.
| Descriptor | Marks |
|---|---|
Identifies bactericidal antibiotics | 1 |
Explains that bactericidal antibiotics kill bacteria by changing the structure of the cell wall/cell membrane/disrupting an essential enzyme | 1 |
Identifies bacteriostatic antibiotics | 1 |
Explains that bacteriostatic antibiotics inhibit growth/prevent reproduction by disrupting protein synthesis | 1 |
The antibodies in breast milk provide a child with
natural active immunity.
artificial passive immunity.
natural passive immunity.
artificial active immunity.
Reveal Answer
natural active immunity.
Natural active immunity occurs when a person's own immune system produces antibodies in response to a natural infection, rather than receiving them from another source.
artificial passive immunity.
Artificial passive immunity involves receiving pre-made antibodies through medical intervention, such as an injection of immunoglobulins or antivenom.
natural passive immunity.
Natural passive immunity occurs when antibodies are transferred naturally from one person to another, such as from a mother to her child through breast milk or across the placenta.
artificial active immunity.
Artificial active immunity is acquired through vaccination, which medically introduces an antigen to stimulate the body's own immune system to produce antibodies.
Middle East respiratory syndrome (MERS) is caused by a virus that does not encode any neuraminidase proteins.
This means that the antiviral drug Relenza would
reduce the number of MERS viral particles released from infected cells.
be useful to consider as a prevention method against MERS infections.
be unlikely to improve the recovery of MERS-infected patients.
target other cell surface proteins of MERS-infected cells.
Reveal Answer
reduce the number of MERS viral particles released from infected cells.
Relenza works by inhibiting neuraminidase to prevent viral release, but since MERS lacks this protein, the drug would not affect the release of MERS viral particles.
be useful to consider as a prevention method against MERS infections.
Because MERS does not have the neuraminidase protein that Relenza targets, the drug would be completely ineffective as a preventative measure.
be unlikely to improve the recovery of MERS-infected patients.
Relenza is a specific neuraminidase inhibitor. Since the MERS virus does not encode neuraminidase, the drug has no target and would not help patients recover.
target other cell surface proteins of MERS-infected cells.
Relenza is highly specific to neuraminidase and does not target or bind to other cell surface proteins on infected cells.