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MYP 3 · Science

Health and Disease (intro)

60 questions across 3 sub-topics

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Pathogens and Infectious Disease The Immune System (basic) Healthy Lifestyle Choices

Pathogens and Infectious Disease 20 questions

QUESTION 1 4 marks Criterion A
Easy

A pathogen is a micro-organism that can cause disease. State the four main types of pathogen, and give one example disease caused by each.

Show complete worked solution

The four main types of pathogen are:

  • Bacteria — e.g. Salmonella food poisoning
  • Viruses — e.g. influenza (flu)
  • Fungi — e.g. athlete's foot
  • Protists (protozoa) — e.g. malaria
QUESTION 2 3 marks Criterion A
Easy

Diseases caused by pathogens can be transmitted (spread) between people in several different ways.

a. Name the method of transmission when a disease spreads through tiny droplets released into the air when an infected person coughs or sneezes.
[1]
b. Name the method of transmission when a disease spreads by touching an infected person or a contaminated surface.
[1]
c. Name the method of transmission when a disease spreads through contaminated food or water.
[1]
Show complete worked solution
(a)
Droplet infection (airborne transmission).
(b)
Direct (or indirect) contact transmission.
(c)
Ingestion (faecal–oral / waterborne transmission).
QUESTION 3 4 marks Criterion A
Easy
DiseaseCaused byType of pathogen
FluInfluenza virus?
MalariaPlasmodium?
Salmonella food poisoningSalmonella bacteria?
Athlete's footTinea fungus?

Copy and complete the table above by identifying the type of pathogen (bacterium, virus, fungus or protist) responsible for each disease.

Show complete worked solution

Flu — virus. Malaria — protist. Salmonella food poisoning — bacterium. Athlete's foot — fungus.

QUESTION 4 5 marks Criterion A
Medium

Bacteria reproduce asexually by a process called binary fission, where one bacterial cell splits into two identical daughter cells. Under ideal warm, moist conditions, a certain species of bacteria divides once every $20\,\text{minutes}$.

a. Starting with a single bacterium, how many bacteria are present after one division (after $20$ minutes)?
[1]
b. Calculate the number of bacteria present after $2$ hours, starting from a single bacterium. Show your working.
[2]
c. Explain why a bacterial infection in the body can grow very rapidly if it is not controlled by the immune system or by medicine.
[2]
Show complete worked solution
(a)
$2$ bacteria.
(b)

Number of divisions in $2$ hours ($120$ min): $$ n = \frac{120}{20} = 6 $$

Number of bacteria: $$ N = 2^{n} = 2^{6} = 64 $$

Answer: $64$ bacteria.

(c)
Because each division doubles the number of bacteria, the population grows exponentially rather than by a fixed amount each time. Early on the increase looks small, but once several divisions have happened the doubling produces enormous numbers very quickly (e.g. one bacterium becomes over $60$ within $2$ hours), which is why an uncontrolled infection can become serious in a short time.
QUESTION 5 4 marks Criterion A
Medium

Explain two differences between bacteria and viruses, in terms of their structure and how they reproduce.

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Structure: bacteria are living single cells, with their own cell wall, cytoplasm and genetic material; viruses are not made of cells at all, are much smaller than bacteria, and are not considered fully "living" outside a host.

Reproduction: bacteria can reproduce independently by binary fission, splitting themselves in two; viruses cannot reproduce on their own — they must invade a living host cell and use the host cell's own machinery to make copies of themselves, which is also why viral infections can destroy host cells as new viruses are released.

QUESTION 6 5 marks Criterion A
Medium

Athlete's foot is caused by a fungal pathogen, and malaria is caused by a protist pathogen that is carried by mosquitoes.

a. Describe how athlete's foot typically spreads between people.
[2]
b. Explain what is meant by a "vector" in the spread of disease, using malaria as your example.
[3]
Show complete worked solution
(a)
It spreads mainly by direct contact with infected skin, or indirect contact with contaminated surfaces such as damp changing-room floors or shared towels/socks, where the warm, moist conditions allow the fungal spores to survive and infect a new host.
(b)
A vector is an organism (often an insect) that carries a pathogen from one host to another. For malaria, a female Anopheles mosquito bites a person already infected with the Plasmodium protist, taking in some of the pathogen along with a blood meal; when the same mosquito later bites a different, uninfected person, it passes the Plasmodium into their bloodstream, spreading the disease without the mosquito itself needing to be harmed by it.
QUESTION 7 6 marks Criterion A
Hard

A single bacterium lands on a piece of food that is left unrefrigerated. Under these warm conditions it divides once every $30\,\text{minutes}$.

a. Write a formula for the number of bacteria, $N$, present after $n$ divisions, starting from a single bacterium.
[2]
b. Calculate the number of bacteria present after $4$ hours.
[2]
c. Food poisoning symptoms often begin once bacteria numbers exceed around $1000$ per gram of food. Estimate, to the nearest $30$ minutes, how long this takes to happen, starting from a single bacterium.
[2]
Show complete worked solution
(a)
$$ N = 2^{n} $$
(b)

$$ n = \frac{4 \times 60}{30} = 8 \text{ divisions} $$

$$ N = 2^{8} = 256 $$

Answer: $256$ bacteria.

(c)

$2^{9} = 512$ (below $1000$), but $2^{10} = 1024$ (above $1000$), so $10$ divisions are needed.

$$ t = 10 \times 30 = 300 \text{ min} = 5\,\text{hours} $$

Answer: about $5$ hours.

QUESTION 8 6 marks Criterion B
Medium

A student wants to investigate whether the concentration of antibacterial hand soap affects how much bacterial growth it prevents. They will grow bacteria on agar plates, place paper discs soaked in different soap concentrations on the agar, and measure the diameter of the clear zone (where no bacteria grow) around each disc after $48$ hours of incubation.

a. State the independent and dependent variables in this investigation.
[2]
b. State two variables that should be controlled, and explain why one of them matters.
[2]
c. Describe how the student should use aseptic technique when setting up this investigation, to keep the test fair and safe.
[2]
Show complete worked solution
(a)
Independent variable: concentration of the antibacterial soap. Dependent variable: diameter of the clear zone (zone of inhibition) around each disc.
(b)
Control: the species/amount of bacteria spread on each plate, the size of the paper discs, the volume of soap solution soaked into each disc, and the incubation temperature and time. Why disc size matters: a larger disc would soak up and release more soap regardless of its concentration, which could produce a bigger clear zone purely because of disc size rather than because that soap is more effective — making the comparison unfair.
(c)
  1. Sterilise the inoculating loop by passing it through a Bunsen burner flame before and after use.
  2. Work near the lit Bunsen burner, which creates an updraft that carries airborne microbes away from the plate.
  3. Lift the petri dish lid only briefly, and tape (do not fully seal) the lid shut afterwards to allow air exchange while limiting contamination.
  4. Incubate the sealed plates at a controlled, safe temperature (below $25\,^{\circ}\text{C}$ in most school labs) to avoid growing pathogens that could infect humans.
QUESTION 9 6 marks Criterion B
Medium

A class wants to model how quickly an infectious disease can spread through a population by physically exchanging liquid samples that represent contact between people, then testing the samples with an indicator to reveal who has become "infected".

a. State the independent and dependent variables for this model investigation.
[2]
b. Describe a method for this model, including the equipment used.
[2]
c. Evaluate this model: state one thing it represents well about real disease spread, and one important limitation.
[2]
Show complete worked solution
(a)
Independent variable: number of contact exchanges (rounds) that take place. Dependent variable: number of people found to be "infected" (indicator turns pink) after each round.
(b)
Each student starts with a small cup of clear liquid; one cup is secretly filled with dilute sodium hydroxide solution to represent the first "infected" person. In each round, students pair up and exchange a small sample of liquid by pouring a little of their cup into their partner's and back again, then move to a new partner for the next round. After a set number of rounds, a few drops of phenolphthalein indicator are added to every cup — a cup turning pink shows that person has become "infected".
(c)
Represents well: it shows how disease can spread rapidly through repeated contact, with the number of "infected" people increasing round by round in a way similar to real outbreaks. Limitation: it does not account for real-world factors such as incubation periods, some people already being immune, hygiene measures (e.g. handwashing) reducing transmission, or the fact that a real pathogen is not evenly and reliably transferred in every single contact.
QUESTION 10 8 marks Criterion B
Hard

A student tested how well three different soaps reduce bacteria on hands. They washed their hands once with each soap, then pressed a finger onto an agar plate and counted the bacterial colonies that grew after incubation. Each soap was tested only once.

a. Identify one variable the student failed to control that could make the comparison between soaps unfair.
[2]
b. Explain why testing each soap only once makes the student's conclusion unreliable, and suggest an improvement.
[3]
c. Suggest a way to make the comparison fairer by accounting for the amount of bacteria present on the hand before washing.
[3]
Show complete worked solution
(a)
They did not control (or state) how long or how vigorously they washed their hands each time — a longer or more thorough wash could reduce bacteria regardless of which soap was used, making it impossible to be sure any difference was really caused by the soap itself.
(b)
A single trial is very vulnerable to random variation — how evenly bacteria happen to be distributed on the finger, how firmly the finger is pressed onto the agar, and natural differences in the amount of bacteria present before washing can all change the colony count by chance, with nothing to do with the soap. This means one result cannot reliably show whether a difference between soaps is real or just due to chance. Improvement: repeat the test at least $3$ times for each soap and calculate a mean colony count, so that random variation is averaged out.
(c)
Take a baseline swab/plate from the same finger before washing with each soap, to measure the starting level of bacteria present that time. The results could then be compared as a percentage reduction in colony count for each soap (comparing before and after), rather than comparing the raw "after" colony counts directly — this accounts for the hand naturally having different amounts of bacteria on it at different times, giving a fairer comparison of how effective each soap actually is.
QUESTION 11 3 marks Criterion C
Easy
Day12345
New measles cases251194

The table shows the number of new measles cases recorded each day during a small outbreak at a school.

a. On which day were the most new cases recorded?
[1]
b. Describe the overall pattern shown by the data across the five days.
[2]
Show complete worked solution
(a)
Day $3$ ($11$ new cases).
(b)
The number of new cases rises from day $1$ to day $3$ (the peak), then falls from day $3$ to day $5$. This rise-then-fall pattern is typical of a contained outbreak, where cases increase as the disease spreads and then decrease as fewer susceptible people remain to be infected, or as control measures (e.g. isolation) take effect.
QUESTION 12 4 marks Criterion C
Medium
Year2000200520102015
Vaccination coverage (%)85909580
Measles cases (national)12000600015009000
a. Describe the relationship shown between vaccination coverage and the number of measles cases across the years given.
[2]
b. Use the data to suggest what most likely happened around $2015$ to cause this change.
[2]
Show complete worked solution
(a)
As vaccination coverage increased from $85\%$ in 2000 to $95\%$ in 2010, the number of measles cases fell sharply, from $12000$ to $1500$. Then, between 2010 and 2015, vaccination coverage dropped to $80\%$, and cases rose sharply again to $9000$ — showing an overall inverse relationship: higher coverage is associated with far fewer cases.
(b)
Vaccination coverage dropped noticeably (from $95\%$ to $80\%$) shortly before cases rose again. This suggests fewer people were vaccinated in the years leading up to 2015 (for example, due to reduced access, a vaccine scare, or public complacency once cases were low), leaving more people susceptible and allowing the disease to spread and cause a new rise in cases.
QUESTION 13 5 marks Criterion C
Medium
Patient123456
Incubation period (days)12131121412

The table shows the incubation period (time between exposure and first symptoms) recorded for six patients during a measles outbreak.

a. Identify the anomalous reading in this table.
[1]
b. Explain how you identified it.
[2]
c. Suggest what should be done with this reading before calculating a mean incubation period for the outbreak.
[2]
Show complete worked solution
(a)
Patient $4$ ($2$ days).
(b)
Every other patient's incubation period clusters closely together, between $11$ and $14$ days. Patient $4$'s value of just $2$ days is far outside this range, breaking the otherwise consistent pattern shown by the rest of the data.
(c)
It should be investigated further rather than simply averaged in — Patient $4$ may have actually been exposed on a different (earlier) date than assumed, or there may be a recording error. If it cannot be explained or corrected, it should be excluded from the calculation of the mean, since including it would give a misleadingly short "typical" incubation period.
QUESTION 14 5 marks Criterion C
Medium

A school has $2000$ students. A vaccination register shows that $1700$ of these students have been vaccinated against measles.

a. Calculate the percentage of students at the school who are vaccinated.
[2]
b. Public health data suggests at least $95\%$ vaccination coverage is needed to achieve herd immunity against measles (protecting even those who are not vaccinated). Using your answer to (a), evaluate whether this school has reached herd immunity, and explain what this means for the school's unvaccinated students.
[3]
Show complete worked solution
(a)
$$ \frac{1700}{2000} \times 100 = 85\% $$
(b)
The school's coverage ($85\%$) is well below the $95\%$ needed for herd immunity, so herd immunity has not been reached. This means unvaccinated students at the school (including anyone unable to be vaccinated, e.g. for a medical reason) remain at meaningful risk of catching measles, since the disease could still circulate widely enough among the $15\%$ unvaccinated students and any susceptible contacts to cause outbreaks, rather than being reliably stopped from spreading by the immunity of the wider group.
QUESTION 15 6 marks Criterion C
Medium
MethodTrial 1Trial 2Trial 3
Water only827985
Soap141117
Hand sanitizer202518

The table shows bacterial colony counts grown from finger swabs taken after washing hands using three different methods, repeated $3$ times each.

a. Calculate the mean colony count for "water only" and for "soap".
[2]
b. Using your means, calculate the percentage reduction in colony count achieved by soap compared to water only.
[2]
c. Calculate the mean colony count for hand sanitizer, and use your results to evaluate which is more effective at reducing bacteria: soap or hand sanitizer.
[2]
Show complete worked solution
(a)

Water only: $\dfrac{82+79+85}{3} = \dfrac{246}{3} = 82$

Soap: $\dfrac{14+11+17}{3} = \dfrac{42}{3} = 14$

(b)
$$ \frac{82 - 14}{82} \times 100 = \frac{68}{82} \times 100 \approx 82.9\% $$
(c)

Sanitizer mean: $\dfrac{20+25+18}{3} = \dfrac{63}{3} = 21$

Percentage reduction vs water: $\dfrac{82-21}{82}\times100 \approx 74.4\%$

Soap gives a larger percentage reduction ($\approx83\%$) than hand sanitizer ($\approx74\%$) in this data, so soap appears more effective at reducing bacteria on hands in this investigation.

QUESTION 16 7 marks Criterion C
Hard
0 2 4 6 8 0 20 40 60 80 Week New cases per week Campaign begins

The graph shows the number of new flu cases recorded each week at a large school, before and after a vaccination campaign began in week $4$.

a. Calculate the average rate of increase in new cases per week between week $0$ and week $4$.
[2]
b. Describe how the number of new cases changed between week $4$ and week $8$.
[2]
c. A student claims this graph proves the vaccination campaign caused the fall in cases. Evaluate this claim, referring to what the data alone can and cannot show.
[3]
Show complete worked solution
(a)
$$ \text{rate} = \frac{70 - 5}{4 - 0} = 16.25 \text{ cases/week} $$
(b)
After the peak of about $70$ cases in week $4$, the number of new cases fell rapidly, dropping to only about $3$ cases by week $8$ — a clear and steady downward trend.
(c)
The data is consistent with the campaign being effective — cases fell sharply very soon after the campaign began. However, a graph like this only shows a correlation (cases fell after the campaign started), not proof of causation. Other factors happening around the same time — such as natural depletion of susceptible people as the outbreak ran its course, improved hygiene measures, or the school being partly closed — could also have contributed to the fall. To be more confident the campaign specifically caused the drop, it would help to compare against a similar school that did not run a vaccination campaign over the same period.
QUESTION 17 6 marks Criterion C
Hard
Plate12345
Colony count3431582933

A student swabbed the same source and spread it onto $5$ identical agar plates to test the consistency (reliability) of their technique.

a. Calculate the mean colony count using all five plates.
[2]
b. Identify the anomalous plate, and explain why it is likely to be inaccurate rather than a genuine result.
[2]
c. Recalculate the mean excluding the anomalous plate, and explain why this is a more reliable estimate.
[2]
Show complete worked solution
(a)
$$ \frac{34+31+58+29+33}{5} = \frac{185}{5} = 37 $$
(b)
Plate $3$ ($58$ colonies) is anomalous. The other four plates cluster tightly together, between $29$ and $34$ colonies, so a value more than $20$ higher than the rest is unlikely to reflect a genuine difference in bacteria transferred — it is far more likely caused by an error such as contamination from unsterile equipment or the lid being left open too long.
(c)

$$ \frac{34+31+29+33}{4} = \frac{127}{4} = 31.75 $$

This is more reliable because it is not skewed by the one plate likely affected by a contamination error, so it better reflects the consistent pattern (bacterial growth) shown by the four plates that agree with each other.

QUESTION 18 5 marks Criterion D
Medium

Antibiotics are highly effective medicines against bacterial infections, but doctors are increasingly advised to prescribe them only when truly necessary, and patients are told to always complete the full course.

Discuss one benefit and one drawback/concern of widespread antibiotic use, referring to the idea of antibiotic resistance.

Show complete worked solution

Benefit: antibiotics have saved millions of lives by effectively curing bacterial infections that were once often fatal, such as pneumonia and infected wounds, and they make many modern medical procedures (like surgery) far safer by preventing and treating infection.

Drawback/concern: overusing antibiotics, or not completing a prescribed course, allows any bacteria with a natural, chance resistance to survive and reproduce, passing that resistance on. Over time, whole populations of bacteria (such as MRSA) can become resistant to multiple antibiotics, making common infections much harder, or in some cases impossible, to treat — which is why using antibiotics responsibly (only when needed, and completing the full course) is important to slow the spread of resistance.

QUESTION 19 6 marks Criterion D
Medium

During the 1918 flu pandemic, the disease took several months to spread between continents by ship. Today, international air travel means an infected person can reach the other side of the world in under $24$ hours — often before any symptoms even appear.

Discuss one benefit and one drawback of widespread modern air travel in relation to the spread of infectious disease.

Show complete worked solution

Benefit: fast international travel and communication also allow a rapid global response to outbreaks — medical experts, vaccines, equipment, and scientific data (such as a new pathogen's genetic sequence) can be shared between countries within days rather than months, helping researchers worldwide collaborate quickly on tracking and treating a new disease.

Drawback: because incubation periods (which can be several days) are often longer than flight times (hours), an infected but symptom-free traveller can unknowingly carry a pathogen to many different countries before an outbreak is even identified. This makes it far harder to contain a new infectious disease than in the past, when the slower speed of travel by ship gave more time for a disease to be identified and contained before it spread far.

QUESTION 20 6 marks Criterion D
Hard

During a serious outbreak of an infectious disease, governments sometimes require people to quarantine (stay away from others) for a period of time, even at the cost of missed school, work, and social contact.

Evaluate the use of quarantine measures during an infectious disease outbreak, discussing one benefit and one drawback/concern.

Show complete worked solution

Benefit: quarantine limits an infected (or possibly infected) person's contact with others during the time they are most likely to spread the pathogen, slowing or preventing further chains of transmission. This is especially valuable for a new disease with no vaccine or treatment yet available, and it helps protect the most vulnerable people (such as the elderly or those with weakened immune systems), who face the greatest risk of serious illness or death if infected.

Drawback/concern: strict quarantine can cause serious harm beyond the disease itself — lost income for workers who cannot do their job remotely, disrupted education, and increased loneliness or mental health difficulties, particularly for people living alone. These real costs mean that quarantine measures need to be balanced carefully against how severe the disease actually is, and are often most fair when combined with extra support, such as financial aid or access to online learning, to reduce the harm they cause.

The Immune System (basic) 20 questions

QUESTION 1 4 marks Criterion A
Easy

State four ways the human body prevents pathogens from entering in the first place (physical/chemical barriers), giving one example of each.

Show complete worked solution
  • Skin — forms a physical barrier that most pathogens cannot cross.
  • Mucus in the airways — traps inhaled pathogens and dust before they reach the lungs.
  • Stomach acid — kills most pathogens swallowed with food or water.
  • Tears and saliva — contain the enzyme lysozyme, which destroys bacterial cell walls.
QUESTION 2 3 marks Criterion A
Easy

Answer the following short questions about the immune system.

a. What is an "antigen"?
[1]
b. What is an "antibody"?
[1]
c. What is the general term for any substance that triggers an immune response?
[1]
Show complete worked solution
(a)
A molecule on the surface of a pathogen (or other cell) that the immune system can recognise as foreign.
(b)
A protein produced by white blood cells (lymphocytes) that binds specifically to one particular antigen, helping to mark or destroy the pathogen carrying it.
(c)
An antigen.
QUESTION 3 3 marks Criterion A
Easy

Name the two main types of white blood cell involved in fighting infection, and briefly state the job of each.

Show complete worked solution

Phagocytes — engulf and digest pathogens directly, by a process called phagocytosis (a fast, non-specific response to any pathogen).

Lymphocytes — produce antibodies that are specific to a particular pathogen's antigens (part of the slower, specific response).

QUESTION 4 4 marks Criterion A
Medium
Phagocytosis 1. Phagocyte approaches pathogen 2. Pathogen engulfed (vesicle forms) 3. Pathogen digested by enzymes

The diagram shows the three stages of phagocytosis, one of the body's defences against pathogens.

a. Describe the process of phagocytosis shown in the diagram, in order.
[2]
b. Explain why phagocytosis is described as "non-specific" (part of the innate immune response).
[2]
Show complete worked solution
(a)
First, the phagocyte detects and moves towards the pathogen. It then surrounds and engulfs the pathogen, trapping it inside a vesicle (a membrane-bound sac) within the cell. Finally, the phagocyte releases digestive enzymes into the vesicle, which break down and destroy the pathogen.
(b)
Phagocytes will engulf and destroy any pathogen they encounter, regardless of its type or antigen — they are not targeted at one particular pathogen. This is different from the antibody response, where a lymphocyte produces antibodies that are specific to one particular antigen shape.
QUESTION 5 4 marks Criterion A
Medium

Explain, using the idea of antigens and antibodies, why a person who has recovered from chickenpox does not usually catch it again, but this same immunity does not protect them from catching a cold (caused by a different virus).

Show complete worked solution
Antibodies are specific to one particular antigen shape, rather like a key fits only one lock. After chickenpox, the body keeps memory cells that recognise the chickenpox virus's specific antigens, so if re-exposed it can produce the matching antibodies almost immediately, destroying the virus before it can cause illness again. A cold is caused by a different virus with a completely different antigen shape, so the antibodies (and memory cells) made against chickenpox do not recognise or fit it, and provide no protection against catching a cold.
QUESTION 6 5 marks Criterion A
Medium

The first time a person is infected by a particular pathogen, it takes several days for the immune system to produce enough antibodies to fight it off — this is called the primary response. If the same pathogen infects the person again later, the response is much faster and stronger — the secondary response.

a. Explain, in terms of cells, why the secondary response is faster than the primary response.
[2]
b. Explain how this idea of memory cells explains why vaccination can protect a person from a disease they have never actually caught.
[3]
Show complete worked solution
(a)
During the primary response, the immune system creates a small number of long-lived memory cells specific to that pathogen's antigen. On re-infection, these memory cells recognise the antigen immediately and multiply rapidly, producing large amounts of the correct antibody much sooner than the first time — when antibody-producing cells first had to be produced essentially "from scratch".
(b)
A vaccine exposes the immune system to a safe form of a pathogen's antigen (e.g. a weakened or inactive pathogen, or just part of it) without causing the actual disease. This triggers a primary response and, importantly, creates memory cells specific to that antigen. If the vaccinated person later meets the real, live pathogen, their immune system can mount a fast, strong secondary response — destroying the pathogen before it has a chance to multiply enough to cause serious illness, even though the person was never actually made ill by the real disease first.
QUESTION 7 6 marks Criterion A
Hard

Active immunity is produced when the body makes its own antibodies (e.g. after infection or vaccination). Passive immunity is gained when ready-made antibodies are given to the body (e.g. antibodies passed from a mother to a baby through breast milk, or given by injection).

a. State one similarity and one difference between active and passive immunity.
[2]
b. Explain why passive immunity gives protection immediately, while active immunity (e.g. from a vaccine) does not.
[2]
c. Explain why passive immunity only provides short-term protection, while active immunity (via memory cells) can provide long-term protection.
[2]
Show complete worked solution
(a)
Similarity: both provide the body with antibodies that can fight a specific pathogen. Difference: in active immunity, the body produces its own antibodies (and creates memory cells for long-term protection); in passive immunity, ready-made antibodies from another source are given directly, and no memory cells are produced.
(b)
Passive immunity introduces ready-made antibodies straight into the bloodstream, so they can act against the pathogen immediately. Active immunity requires the body to first recognise the antigen and go through the primary response — a process that can take days to weeks — before enough of its own antibodies are produced for full protection.
(c)
The antibodies introduced in passive immunity are gradually broken down by the body over weeks or months, and because no memory cells were made, the body cannot produce more once they are gone. In active immunity, memory cells can persist for years (sometimes a lifetime), allowing a fast secondary response whenever the pathogen is met again, giving much longer-lasting protection.
QUESTION 8 6 marks Criterion B
Medium

Lysozyme is an enzyme found in tears, saliva and mucus that breaks down bacterial cell walls. A student wants to investigate how temperature affects how quickly lysozyme can clear a cloudy bacterial suspension (as bacteria are destroyed, the suspension becomes clearer).

a. State the independent and dependent variables in this investigation.
[2]
b. State two variables that should be controlled, and explain why one of them matters.
[2]
c. Describe a method for this investigation, including the equipment used.
[2]
Show complete worked solution
(a)
Independent variable: temperature of the reaction (e.g. tested in water baths at $10, 20, 37, 50$ and $70\,^{\circ}\text{C}$). Dependent variable: time taken for the bacterial suspension to reach a set level of clarity.
(b)
Control: the concentration/volume of lysozyme solution used, the concentration/volume of bacterial suspension used, and the pH of the mixture. Why lysozyme concentration matters: if more lysozyme were used in one test tube than another, that tube could clear faster simply because more enzyme is present, regardless of temperature — making the comparison unfair.
(c)
Set up test tubes each containing the same volume and concentration of bacterial suspension and lysozyme solution, and place one tube in each of several water baths held at different temperatures. Using a light sensor/colorimeter (or visual comparison against a reference chart), record the time taken for each tube to reach a set level of clarity. Repeat each temperature $3$ times and calculate a mean time.
QUESTION 9 6 marks Criterion B
Medium

A class builds a simple model of antibody specificity: each "antigen" is a uniquely-shaped paper cut-out, and each matching "antibody" is a card with a cut-out slot that only that one antigen shape fits into (like a lock and key). Students want to investigate whether having more different antigen shapes mixed together makes it take longer to find the correct matching antibody card for one target antigen.

a. State the independent and dependent variables.
[2]
b. State two variables that should be controlled, and explain why one of them matters.
[2]
c. Describe how repeating the search for the same target antigen a second time could model what actually happens in a secondary immune response.
[2]
Show complete worked solution
(a)
Independent variable: number of different antigen shapes mixed together (e.g. $5, 10, 15, 20$). Dependent variable: time taken to find the matching antibody card for the target antigen.
(b)
Control: the same target antigen shape used each time, the same student doing the searching each time, and cards shuffled in the same way. Why using the same student matters: if a different person searched each time, natural differences in searching speed or skill between people (not the number of shapes present) could affect the results, making the comparison unfair.
(c)
Having already located the correct matching card once, a person is likely to remember roughly what it looked like (or where it was), so they find it much faster the second time. This models how memory cells allow the body to produce the correct antibody far more quickly on re-exposure to the same antigen, rather than having to "search" (produce antibodies) from scratch again.
QUESTION 10 8 marks Criterion B
Hard

A student read that people who sleep less than $6$ hours a night get more colds. To test this at their school, they asked $8$ friends how many hours they usually slept, and how many colds they had that year, then compared the results between those sleeping under $6$ hours and those sleeping over $6$ hours.

a. Identify one problem with using a sample of only $8$ friends for this investigation.
[2]
b. Identify one variable, other than sleep, that could also affect how many colds a person catches, and explain why this makes the investigation's conclusion unreliable.
[3]
c. Suggest two specific improvements to make this investigation more scientifically reliable.
[3]
Show complete worked solution
(a)
The sample size is far too small — results from just $8$ people could easily be due to individual differences or chance rather than a genuine, reliable link between sleep and colds, and cannot be confidently generalised to a larger population.
(b)
For example: diet, stress levels, hand-washing habits, or how much close contact a person has with others (e.g. siblings, crowded classes). Since none of these were controlled or recorded, any apparent link found between sleep and colds could actually be caused, partly or fully, by one of these other factors instead — so the investigation cannot reliably conclude that sleep itself is the cause.
(c)
Use a much larger, more random sample (not only friends, who may already share similar lifestyles or habits); collect data over a longer, consistent time period; use an objective method of measuring sleep (e.g. a sleep-tracking device) rather than self-reported estimates, which can be inaccurate; and try to record or control for other relevant variables (such as those in part (b)) so their effect can be taken into account.
QUESTION 11 3 marks Criterion C
Easy
Day035710
White blood cell count (thousand cells/mm³)6614107

The table shows a patient's white blood cell count over $10$ days, during which they caught and recovered from an infection.

a. On which day was the white blood cell count highest?
[1]
b. Describe how the white blood cell count changes across the $10$ days, and suggest what is happening in the body to explain this pattern.
[2]
Show complete worked solution
(a)
Day $5$ ($14$ thousand cells/mm³).
(b)
The count stays steady at first (day $0$ to day $3$), then rises sharply to a peak by day $5$, then gradually falls back towards its starting level by day $10$. This pattern reflects the immune system producing many more white blood cells to fight the infection once it begins, and the count falling again as the infection is successfully cleared.
QUESTION 12 5 marks Criterion C
Medium
0 10 20 30 40 0 25 50 75 100 Time (days) Antibody concentration (units) 1st exposure (day 0) 2nd exposure

The graph shows the concentration of a specific antibody in a person's blood following a first exposure to a pathogen at day $0$, and a second exposure to the same pathogen at day $25$.

a. What was the maximum (peak) antibody concentration reached after the first exposure, and at approximately what day?
[1]
b. Compare the peak antibody concentration and the time taken to reach it after the second exposure with the first exposure, using values from the graph.
[2]
c. Explain what is happening in the immune system that causes this difference between the two responses.
[2]
Show complete worked solution
(a)
About $20$ units, at approximately day $15$.
(b)
After the second exposure, the antibody concentration peaks much higher (about $90$ units, compared to about $20$ units after the first exposure) and reaches this peak much faster (within about $5$ days of re-exposure, compared to about $15$ days for the first response).
(c)
Memory cells produced during the first (primary) response remain in the body long afterwards. On the second exposure, these memory cells recognise the same antigen immediately and multiply rapidly, producing a much larger quantity of antibody, much faster, than in the initial response — when the correct antibody-producing cells had to be made for the very first time.
QUESTION 13 5 marks Criterion C
Medium
Day123456
Body temperature (°C)37.838.939.438.637.537.0

The table shows a patient's body temperature recorded once a day during an infection. Normal resting body temperature is $37.0\,^{\circ}\text{C}$.

a. Calculate how many degrees above the normal resting temperature ($37.0\,^{\circ}\text{C}$) the peak fever reached.
[2]
b. A fever occurs when the body deliberately raises its internal temperature to help fight infection. Suggest two ways a higher body temperature could help the immune system fight a pathogen.
[3]
Show complete worked solution
(a)
Peak temperature $= 39.4\,^{\circ}\text{C}$ (Day 3). $$ 39.4 - 37.0 = 2.4\,^{\circ}\text{C} $$
(b)
A raised temperature can slow the reproduction rate of some pathogens, since many are adapted to grow best at normal body temperature and reproduce less effectively when it rises. It can also speed up the chemical reactions involved in the immune response, such as how quickly white blood cells work and antibodies are produced, helping the body clear the infection faster.
QUESTION 14 5 marks Criterion C
Medium
GroupNumber of peopleNumber who caught the disease
Vaccinated50015
Unvaccinated500210
a. Calculate the percentage of each group that caught the disease.
[2]
b. Using your answers to (a), evaluate how effective the vaccine appears to be, and suggest one reason (other than the vaccine having no effect) why a small number of vaccinated people still caught the disease.
[3]
Show complete worked solution
(a)

Vaccinated: $\dfrac{15}{500}\times100 = 3\%$

Unvaccinated: $\dfrac{210}{500}\times100 = 42\%$

(b)
The vaccine appears highly effective: the infection rate in the vaccinated group ($3\%$) is far lower than in the unvaccinated group ($42\%$) — a fourteen-fold difference — strongly suggesting vaccination gives substantial protection. Vaccinated people can still occasionally become infected because no vaccine gives $100\%$ protection to every individual: immune response strength varies between people, some may respond less strongly to the vaccine, or may have been exposed to an unusually high dose of the pathogen.
QUESTION 15 6 marks Criterion C
Medium
Cell typePhagocytesLymphocytesOther
Number (out of 200 counted)1306010

The table shows a differential count of $200$ white blood cells from a blood sample taken from a patient during a bacterial infection.

a. Calculate the percentage of the $200$ counted white blood cells that were phagocytes.
[2]
b. Calculate the percentage that were lymphocytes.
[2]
c. Suggest why phagocytes might make up a larger proportion of white blood cells than lymphocytes at this early stage of a bacterial infection.
[2]
Show complete worked solution
(a)
$$ \frac{130}{200}\times100 = 65\% $$
(b)
$$ \frac{60}{200}\times100 = 30\% $$
(c)
Phagocytes provide a fast, non-specific first response to any pathogen and can be mobilised in large numbers very quickly once an infection begins. Lymphocytes, which produce antibodies specific to that pathogen, take longer to multiply into large numbers as part of the slower, more specific primary response — so early in an infection, the proportion of phagocytes is often higher.
QUESTION 16 7 marks Criterion C
Hard
Patient12345
Antibody titre (units)8279852081

The table shows antibody titre (antibody level) measured in $5$ patients $10$ days after receiving the same vaccine.

a. Calculate the mean antibody titre using all $5$ results.
[2]
b. Identify the anomalous result, and explain why the mean calculated in (a) may not fairly represent the typical vaccine response.
[2]
c. Suggest two different explanations for why Patient $4$'s result might be genuinely low (rather than a testing error), and explain what a researcher should do before deciding whether to exclude this result.
[3]
Show complete worked solution
(a)
$$ \frac{82+79+85+20+81}{5} = \frac{347}{5} = 69.4 $$
(b)
Patient $4$'s result ($20$) is anomalous — far below the other four results, which cluster between $79$ and $85$. Because it is so different from the rest, including it pulls the calculated mean down substantially, making it unrepresentative of how most people in the group actually responded.
(c)
Explanations: Patient $4$ could have a genuinely weaker immune response for a biological reason, such as an existing health condition, older age, or not receiving the full vaccine dose correctly. Before excluding the result, a researcher should re-test the sample to check whether $20$ was simply a measurement or lab error, and check the patient's records for any factor that could genuinely explain a weaker response — only excluding the result if a testing error is confirmed, since a genuinely low response is still real, important data for understanding how well the vaccine works across a whole population.
QUESTION 17 7 marks Criterion C
Hard
Vaccination coverage (%)506070809095
R number2.52.01.51.10.80.5

The table shows how a disease's reproduction number, $R$ (the average number of other people one infected person passes the disease to), changes with vaccination coverage in a population.

a. Using the data, estimate the minimum vaccination coverage needed to bring $R$ below $1$ (the point at which an outbreak can no longer sustain itself and cases decline).
[2]
b. Explain what an $R$ number of less than $1$ means for how the disease spreads through the population.
[2]
c. A newspaper claims: "Once $95\%$ of the population is vaccinated, the disease will disappear completely." Evaluate this claim using the data and your understanding of the limits of vaccination.
[3]
Show complete worked solution
(a)
$R$ falls below $1$ somewhere between $80\%$ coverage ($R=1.1$) and $90\%$ coverage ($R=0.8$) — a reasonable estimate is around $85\%$ coverage.
(b)
An $R$ value below $1$ means each infected person passes the disease to fewer than one other person on average, so the total number of new cases decreases over time and the outbreak eventually dies out, rather than continuing to grow.
(c)
The data supports that $95\%$ coverage gives strong control ($R=0.5$, well below $1$, so cases should fall rapidly). However, "disappear completely" overstates what the data shows: some individuals cannot be vaccinated for medical reasons, or the vaccine may not work perfectly in everyone, so susceptible people remain; the pathogen can still exist and cause occasional cases, especially if coverage is uneven between different areas or groups, or falls over time. True global elimination has only been achieved for a very small number of diseases (such as smallpox) after sustained, worldwide vaccination effort — not simply from crossing one coverage threshold in one population.
QUESTION 18 5 marks Criterion D
Medium

Some countries require children to be vaccinated against certain diseases before they can attend school, while others rely only on voluntary vaccination.

Discuss one benefit and one drawback/concern of making vaccination against a serious infectious disease compulsory for school attendance.

Show complete worked solution

Benefit: mandatory vaccination policies tend to achieve much higher vaccination coverage across a population than voluntary schemes, which is important for reaching the herd immunity threshold and protecting vulnerable people who cannot be vaccinated themselves (e.g. due to allergies or a weakened immune system) — high coverage has historically sharply reduced or even eliminated school outbreaks of diseases like measles.

Drawback/concern: mandatory vaccination removes an element of personal or parental choice over a medical decision, which some families object to on medical, religious, or personal grounds; excluding unvaccinated children from school can also disadvantage their education. This means such policies need to balance protecting public health with respecting individual rights, often through exemption systems for genuine medical reasons.

QUESTION 19 6 marks Criterion D
Medium

When a patient receives an organ transplant (e.g. a kidney), their immune system usually recognises the new organ as "foreign" and attacks it, because it does not carry the patient's own antigens. To prevent this, patients are given immunosuppressant drugs, which deliberately weaken the immune system's response.

Discuss one benefit and one drawback/concern of using immunosuppressant drugs after an organ transplant.

Show complete worked solution

Benefit: by weakening the specific immune attack on the transplanted organ's antigens, immunosuppressant drugs allow the new organ to survive and function in the patient's body long-term, which can save or dramatically improve the life of a patient with organ failure who would otherwise have very limited treatment options.

Drawback/concern: because these drugs weaken the immune system generally, not just the response to the transplanted organ, patients become significantly more vulnerable to infections from ordinary pathogens that a healthy immune system would normally deal with easily. This means transplant patients often need extra precautions and can become seriously ill from infections that would be minor in most other people.

QUESTION 20 6 marks Criterion D
Hard

Modern sanitation, clean water, and hygiene practices have dramatically reduced deaths from infectious disease over the last century. Some scientists have also proposed the "hygiene hypothesis" — the idea that children in very low-pathogen-exposure environments may have higher rates of allergies and some autoimmune conditions, possibly because their immune systems have less early exposure to germs to "train" them properly.

Evaluate the impact of modern hygiene practices on health, discussing both a benefit and a possible concern.

Show complete worked solution

Benefit: clean water, sanitation, and hygiene practices (handwashing, food safety, sewage treatment) have been one of the single biggest contributors to increased life expectancy and reduced child mortality worldwide, by dramatically cutting rates of severe infectious diseases such as cholera, typhoid, and diarrhoeal illnesses that once killed huge numbers of people, especially children.

Concern: the hygiene hypothesis is a proposed explanation, still researched and debated by scientists rather than fully proven, suggesting that significantly reduced early-life exposure to a wide variety of harmless microbes may be linked to the rise in allergies, asthma, and some autoimmune conditions seen in many developed countries over recent decades, since the immune system may need some level of early challenge to develop properly. However, this idea must be weighed very carefully against the proven, very large benefits of hygiene in preventing serious infectious disease — reducing hygiene practices generally would not be a safe way to address this concern.

Healthy Lifestyle Choices 20 questions

QUESTION 1 4 marks Criterion A
Easy

State four of the main nutrient groups found in a balanced diet, giving one food source for each.

Show complete worked solution

Any four of, e.g.:

  • Carbohydrates — e.g. bread, pasta, rice (main energy source)
  • Proteins — e.g. meat, fish, beans, eggs (growth and repair of tissues)
  • Fats — e.g. oils, butter, nuts (energy store, insulation)
  • Vitamins and minerals — e.g. fruit and vegetables (many roles, e.g. Vitamin C for immune function, calcium for bones)
  • Fibre — e.g. wholegrain foods, vegetables (aids digestion)
  • Water — essential for almost all body processes
QUESTION 2 3 marks Criterion A
Easy

Answer the following short questions about lifestyle and health.

a. State one health benefit of regular physical exercise.
[1]
b. State one health risk linked to a diet high in saturated fat and sugar, eaten regularly over a long period.
[1]
c. State one health risk linked to smoking tobacco.
[1]
Show complete worked solution
(a)
For example: it strengthens the heart and muscles, helps maintain a healthy body weight, or improves mental health and reduces stress. (Any one valid benefit.)
(b)
Increased risk of obesity, type $2$ diabetes, and cardiovascular (heart) disease.
(c)
Increased risk of lung cancer, other lung disease, and cardiovascular disease.
QUESTION 3 3 marks Criterion A
Easy

Define "Body Mass Index (BMI)" and state the formula used to calculate it.

Show complete worked solution

BMI is a number calculated from a person's mass and height, used as a simple (though imperfect) screening tool to estimate whether someone's weight is in a healthy range relative to their height.

$$ BMI = \frac{\text{mass (kg)}}{[\text{height (m)}]^{2}} $$

QUESTION 4 5 marks Criterion A
Medium

A $14$-year-old has a mass of $58\,\text{kg}$ and a height of $1.60\,\text{m}$.

a. Calculate this person's BMI, showing your working, and give your answer to $1$ decimal place.
[3]
b. The healthy BMI range for adults is often quoted as $18.5$–$24.9$. Explain why BMI values for children and teenagers are not compared directly to this same fixed adult range.
[2]
Show complete worked solution
(a)

$$ BMI = \frac{\text{mass}}{\text{height}^2} = \frac{58}{1.60^2} = \frac{58}{2.56} $$

Answer: $BMI = 22.7$ (1 d.p.)

(b)
Children and teenagers are still growing, so what counts as a healthy amount of body mass for their height changes naturally with age and sex as they develop. For young people, BMI is instead compared to age- and sex-specific growth charts/percentiles, rather than to one single fixed adult range.
QUESTION 5 4 marks Criterion A
Medium

Explain, in terms of energy intake and energy use, why a person who regularly eats more food energy (calories) than their body uses is likely to gain weight over time, and what must change for them to lose weight instead.

Show complete worked solution
Energy from food that is not used by the body (for processes like movement, exercise, and keeping warm) is stored, mainly as fat; if food energy intake regularly and consistently exceeds the energy the body uses, this leads to a gradual increase in stored body fat and weight gain over time. To lose weight, a person needs to create an energy deficit — either by reducing food energy intake, increasing energy used through physical activity, or both — so that the body must draw on its stored energy reserves (fat) to make up the difference, causing weight to decrease over time.
QUESTION 6 5 marks Criterion A
Medium

Regularly drinking alcohol in large amounts is linked to several long-term health problems.

a. Name one organ that can be seriously damaged by long-term heavy alcohol use, and state the effect on it.
[2]
b. Explain one immediate (short-term) effect of alcohol on the body, and one reason why this makes certain activities dangerous.
[3]
Show complete worked solution
(a)
The liver — heavy, long-term alcohol use can cause liver damage/scarring (cirrhosis), reducing the liver's ability to filter toxins from the blood.
(b)
Alcohol is a depressant that slows down the nervous system, reducing reaction time and impairing judgement and coordination. This makes activities such as driving extremely dangerous, since a slower reaction time and impaired judgement make it much harder to react safely to hazards on the road, increasing the risk of accidents.
QUESTION 7 6 marks Criterion A
Hard

A packet of crisps contains $840\,\text{kJ}$ of energy per $100\,\text{g}$ serving. A teenager eats a $50\,\text{g}$ portion. Their recommended daily energy intake is $9000\,\text{kJ}$.

a. Calculate the energy, in kJ, provided by the $50\,\text{g}$ portion of crisps.
[2]
b. Calculate what percentage of the teenager's recommended daily energy intake this portion provides.
[2]
c. If the teenager eats this same $50\,\text{g}$ portion every day as an "extra" snack, on top of otherwise exactly meeting their daily energy needs, estimate the mass of extra body fat this could add per week, given that roughly $32000\,\text{kJ}$ of excess energy is stored as approximately $1\,\text{kg}$ of body fat.
[2]
Show complete worked solution
(a)
$$ 840 \times \frac{50}{100} = 420\,\text{kJ} $$
(b)
$$ \frac{420}{9000}\times100 \approx 4.7\% $$
(c)

Weekly excess energy: $$ 420 \times 7 = 2940\,\text{kJ} $$

Mass of fat stored: $$ \frac{2940}{32000} \approx 0.092\,\text{kg} \ (\approx 92\,\text{g}) $$

QUESTION 8 6 marks Criterion B
Medium

A student wants to investigate how the intensity of exercise affects heart rate recovery time (the time taken for heart rate to return to its resting level after exercise stops).

a. State the independent and dependent variables in this investigation.
[2]
b. State two variables that should be controlled, and explain why one of them matters.
[2]
c. Describe a method for this investigation, including the equipment used.
[2]
Show complete worked solution
(a)
Independent variable: intensity of exercise (e.g. walking, jogging, running for a fixed time). Dependent variable: time taken for heart rate to return to the resting value after exercise stops.
(b)
Control: the same person (or people of similar fitness) tested each time, the same duration of exercise, and the same method of measuring heart rate. Why using the same person matters: if different people were tested at each intensity, natural differences in fitness between people could affect recovery time regardless of the exercise intensity being tested, making the comparison unfair.
(c)
First measure and record the person's resting heart rate. For each intensity level, have them exercise for a fixed time (e.g. $3$ minutes), then immediately measure their heart rate every $30$ seconds after stopping, using a heart rate monitor (or manual pulse count), until it returns to the resting value. Repeat each intensity $3$ times, allowing full recovery and equal rest between trials, and calculate a mean recovery time.
QUESTION 9 6 marks Criterion B
Medium

A student wants to compare the sugar content of different breakfast cereals using Benedict's solution, which changes colour from blue towards orange/brick-red when heated with a reducing sugar — the more sugar present, the further the colour change progresses.

a. State the independent and dependent variables.
[2]
b. State two variables that should be controlled, and explain why one of them matters.
[2]
c. Suggest one limitation of judging colour change by eye (rather than with a colorimeter) to compare sugar content, and how this could be improved.
[2]
Show complete worked solution
(a)
Independent variable: type/brand of cereal tested. Dependent variable: colour reached (or a numerical absorbance reading, if using a colorimeter) after the Benedict's test, used to rank sugar content.
(b)
Control: the same mass of cereal sample dissolved in the same volume of water, the same volume/concentration of Benedict's solution added, and the same heating time and temperature. Why heating time matters: if heating time varied between samples, a sample with less sugar but heated for longer might show a more advanced colour change than a sugarier sample heated for less time, giving a false impression of which cereal has more sugar.
(c)
Judging colour by eye is subjective and imprecise, especially when comparing two samples that are both quite orange/red. A colorimeter would give a numerical light-absorbance reading for each sample, allowing a much more precise, objective comparison of the relative sugar content between the cereals.
QUESTION 10 8 marks Criterion B
Hard

A magazine reported: "Students who eat breakfast get better exam grades." The study behind this asked $30$ students at one high-achieving school whether they usually ate breakfast, and compared this to their exam grades that year.

a. Identify one problem with using only $30$ students from a single high-achieving school for this investigation.
[2]
b. Identify one variable, other than breakfast, that could affect both a student's likelihood of eating breakfast and their exam grades, and explain why this makes it hard to conclude that breakfast itself caused better grades.
[3]
c. Suggest a way to design a fairer, more controlled investigation to test whether breakfast really improves exam performance.
[3]
Show complete worked solution
(a)
The sample is small and drawn from just one (already high-achieving) school, which may not be representative of students more generally — findings from this particular population cannot be safely generalised to all students.
(b)
For example, family income/home routine: students from more stable, well-resourced homes may be more likely to have a regular breakfast routine, and may also have more support, resources, and lower stress affecting their studying and exam performance. Because this other factor could influence both variables, a link found between breakfast and grades does not prove breakfast caused the better grades — it could really be caused by this other underlying (confounding) factor.
(c)
Take a large, more diverse group of students who are similar in relevant ways (e.g. similar background and prior grades), and randomly assign half to eat a standard breakfast and half to skip it, keeping other factors as similar as possible between the groups. Then compare their performance on a standardised test. Random assignment helps ensure the two groups do not systematically differ in other confounding ways, making it fairer to attribute any grade difference specifically to breakfast.
QUESTION 11 3 marks Criterion C
Easy
DayMonTueWedThuFriSatSun
Steps walked450062008100120007300152009800

The table shows the number of steps a person walked each day over one week.

a. On which day did the person walk the most steps?
[1]
b. A common recommendation is at least $10{,}000$ steps per day. On how many of the seven days did the person reach this target, and which days were they?
[2]
Show complete worked solution
(a)
Saturday ($15200$ steps).
(b)
$2$ days: Thursday ($12000$) and Saturday ($15200$).
QUESTION 12 5 marks Criterion C
Medium
Day12345
Sugar consumed (g)4562387150

The table shows one person's added sugar intake, recorded over $5$ days. A common guideline recommends a maximum of about $30\,\text{g}$ of added sugar per day for a teenager.

a. Calculate the mean daily sugar intake across the $5$ days.
[2]
b. Compare the mean value you calculated to the recommended daily maximum of $30\,\text{g}$, and evaluate what this data suggests about this person's diet over the $5$ days.
[3]
Show complete worked solution
(a)
$$ \frac{45+62+38+71+50}{5} = \frac{266}{5} = 53.2\,\text{g} $$
(b)
The mean intake ($53.2\,\text{g}$) is substantially higher than the $30\,\text{g}$ recommended maximum — nearly double — and every single day recorded exceeds the limit, even the lowest day ($38\,\text{g}$). This suggests a consistent, ongoing pattern of high sugar consumption, not just an occasional treat, which over time is linked to an increased risk of weight gain, tooth decay, and type $2$ diabetes.
QUESTION 13 5 marks Criterion C
Medium
ActivityWalkingCyclingRunningSwimming
Energy used per 30 min (kJ)60090015001100

A chocolate bar contains $1200\,\text{kJ}$ of energy. The table shows the approximate energy used by $30$ minutes of different activities.

a. Calculate how many minutes of running would be needed to use up the energy in the chocolate bar.
[2]
b. Calculate how many minutes of walking would be needed for the same amount of energy, and use this comparison to explain why relying on exercise alone to "burn off" high-energy snack foods is not usually a very efficient approach to weight management.
[3]
Show complete worked solution
(a)

Rate: $\dfrac{1500}{30} = 50\,\text{kJ/min}$

Time: $\dfrac{1200}{50} = 24\,\text{minutes}$

(b)

Rate: $\dfrac{600}{30} = 20\,\text{kJ/min}$. Time: $\dfrac{1200}{20} = 60\,\text{minutes}$.

Even a fairly high-energy snack ($1200\,\text{kJ}$) takes a full hour of walking (or still $24$ minutes of running) to use up. This shows how much easier and quicker it is to consume excess energy through food than to use it up through exercise — which is why a balanced diet is generally considered at least as important as exercise for managing weight, rather than relying only on exercising more to compensate for a poor diet.

QUESTION 14 5 marks Criterion C
Medium
Sleep (hours)56789
Errors made in reaction time test97433
a. Describe the relationship shown between hours of sleep and the number of errors made in the reaction time test.
[2]
b. Based on this data, estimate the amount of sleep that seems to give the best balance of good performance without needing excessive extra sleep, and justify your choice using the data.
[3]
Show complete worked solution
(a)
As hours of sleep increase from $5$ to $8$, the number of errors made generally decreases ($9 \to 7 \to 4 \to 3$) — more sleep is associated with fewer errors (better performance). Beyond $8$ hours (at $9$ hours), the number of errors levels off rather than continuing to fall.
(b)
Around $8$ hours. Going from $7$ to $8$ hours still shows a clear improvement ($4$ to $3$ errors), but going from $8$ to $9$ hours shows no further improvement ($3$ to $3$ errors) — suggesting $8$ hours already captures most of the benefit, and further additional sleep does not appear to keep improving performance in this data.
QUESTION 15 6 marks Criterion C
Medium
StudentMass (kg)Height (m)
A501.55
B701.60
C451.50
D801.75
a. Calculate the BMI for Student A and Student D, to $1$ decimal place.
[3]
b. Student D is a competitive rugby player with a very high proportion of muscle mass. Explain why Student D's BMI value alone might give a misleading impression of their health, and suggest what additional information would give a fairer picture.
[3]
Show complete worked solution
(a)

Student A: $\dfrac{50}{1.55^2} = \dfrac{50}{2.4025} \approx 20.8$

Student D: $\dfrac{80}{1.75^2} = \dfrac{80}{3.0625} \approx 26.1$

(b)
BMI only uses total mass and height, so it cannot distinguish between mass from muscle and mass from fat. Since muscle is denser than fat, a very muscular person can have a BMI in the "overweight" range purely because of muscle, not excess body fat — giving a misleading impression that they are unhealthy. Additional useful information could include body fat percentage (e.g. from skinfold callipers or bioelectrical impedance) or waist circumference, which more directly reflect body fat levels rather than total mass.
QUESTION 16 7 marks Criterion C
Hard
Day12345
Resting heart rate (bpm)6870669569

A student recorded their resting heart rate on five consecutive mornings, to establish a baseline before starting a new fitness programme.

a. Calculate the mean resting heart rate using all five readings.
[2]
b. Identify the anomalous reading, and suggest one possible reason for it.
[2]
c. Explain why excluding this anomalous reading before calculating a "baseline" resting heart rate is important for fairly judging whether the fitness programme has been effective.
[3]
Show complete worked solution
(a)
$$ \frac{68+70+66+95+69}{5} = \frac{368}{5} = 73.6\,\text{bpm} $$
(b)
Day $4$ ($95\,\text{bpm}$) is anomalous — the other four readings cluster between $66$ and $70\,\text{bpm}$. A possible reason is that the student may have been ill, stressed, recently active, or had caffeine before this particular measurement, temporarily raising their heart rate above its normal resting value.
(c)
A fitness programme is often judged effective if resting heart rate decreases over time, since this can indicate a stronger, more efficient heart. If the anomalous high reading were included in the baseline mean, it would artificially inflate the starting baseline — making any later decrease in resting heart rate look bigger than it truly is, giving a misleading impression of how much the programme has actually improved fitness. Excluding it and using the more consistent, typical readings ($66$–$70\,\text{bpm}$) gives a fairer, more accurate baseline to compare future measurements against.
QUESTION 17 7 marks Criterion C
Hard
Year20002005201020152020
Average daily screen time (hours)2.53.54.55.56.5
Childhood obesity rate (%)1014172125
a. Describe the trend shown by the data between average daily screen time and childhood obesity rate from 2000 to 2020.
[2]
b. Calculate the increase in childhood obesity rate, in percentage points, between 2000 and 2020.
[2]
c. A news headline claims "This data proves screen time causes childhood obesity." Evaluate this claim, referring to what this type of data can and cannot show.
[3]
Show complete worked solution
(a)
Both average daily screen time and childhood obesity rate have risen steadily and consistently together over the $20$-year period: screen time more than doubled (from $2.5$ to $6.5$ hours), while obesity rate also rose sharply (from $10\%$ to $25\%$).
(b)
$$ 25 - 10 = 15 \text{ percentage points} $$
(c)
The data shows a strong correlation: both variables have risen together consistently over the same period, which is consistent with screen time contributing to obesity (e.g. through less physical activity or snacking while using screens). However, correlation alone cannot prove causation: many other things also changed over this same $20$ years (e.g. changes in diet, less outdoor play generally, greater availability of processed food), any of which could be part or all of the real cause. This data alone does not prove screen time itself causes the rise in obesity — a controlled study directly comparing groups with different screen time but similar other habits would be needed to test causation more rigorously.
QUESTION 18 6 marks Criterion D
Medium

Several countries have introduced a "sugar tax" — an extra tax added to sugary soft drinks, making them more expensive, with the aim of reducing consumption and improving public health.

Discuss one benefit and one drawback/concern of a sugar tax on soft drinks.

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Benefit: making sugary drinks more expensive tends to reduce how much people buy and consume, particularly among those most sensitive to price such as younger people and lower-income households. This can reduce sugar intake across a population and, over time, help lower rates of obesity, type $2$ diabetes, and tooth decay linked to high sugar consumption — some countries introducing such a tax have reported measurable falls in sugary drink sales soon afterwards.

Drawback/concern: a flat tax like this affects lower-income households proportionally more than wealthier ones, since the extra cost is a bigger share of a smaller income (it is a "regressive" tax), meaning it could place a heavier financial burden on people who already have less money, without necessarily changing everyone's habits equally. Critics argue it may be fairer to combine the tax with education programmes, or make healthier options cheaper, rather than relying on cost alone.

QUESTION 19 6 marks Criterion D
Medium

Many countries restrict how junk food (high in sugar, salt, or fat) can be advertised to children, for example by banning such adverts during children's television programmes.

Discuss one benefit and one drawback/concern of restricting junk food advertising aimed at children.

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Benefit: children are generally less able than adults to critically evaluate advertising, and are shown to be strongly influenced by what they see advertised. Restricting junk food adverts aimed at them can reduce "pester power" (children asking parents to buy advertised products) and reduce children's exposure to persuasive messaging encouraging poor food choices, supporting healthier eating habits and helping address rising childhood obesity rates.

Drawback/concern: such restrictions can be difficult and costly to enforce fully, especially given how much advertising children now see through online video, social media, and games rather than just traditional TV, meaning the policy may have limited real-world effect unless regularly updated and enforced across all media. Food and advertising companies may also argue the restrictions unfairly limit legitimate business activity and reduce parental choice/responsibility.

QUESTION 20 6 marks Criterion D
Hard

Fitness tracking apps and wearable devices (e.g. smartwatches) let users track their daily steps, exercise, sleep, and even heart rate, and social media is now full of health and fitness content aimed at teenagers and young people.

Evaluate the impact of fitness tracking technology and social media health content on teenagers, discussing both a benefit and a concern.

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Benefit: fitness trackers can give teenagers clear, motivating, real-time feedback on their activity levels, sleep, and progress towards healthy goals, such as reaching a daily step count, which can genuinely help build awareness of and encourage regular exercise and better sleep habits from a young age. Social media can also spread useful, accessible health information and connect people with supportive fitness communities.

Concern: not all health information shared on social media is accurate or evidence-based, and constant exposure to idealised images and extreme fitness/diet content can contribute to unhealthy comparisons, body image issues, and, in some cases, disordered eating patterns among teenagers, who may be especially vulnerable to this kind of social pressure during adolescence. Relying heavily on a device's numbers can also become an unhealthy obsession for some users rather than a helpful tool, so this technology needs to be used thoughtfully, ideally alongside reliable guidance from trusted adults or health professionals, rather than uncritically.