Global Challenges: Synthesis and Exam Skills

You have now worked through the whole of Topic B6 of OCR Gateway Combined Science A — health and disease, pathogens, the immune system and vaccination, developing new medicines, non-communicable disease, feeding the population and protecting the environment. This final lesson pulls it all together as one big idea: applying biology to real-world global challenges. It shows how the three strands connect, drills the data and graph skills on disease and risk factors that earn reliable marks, sharpens the correlation-versus-cause reasoning, and warns you about the misconceptions that catch students out. Treat it as a revision and exam-technique session rather than new content.

By the end you should be able to see how the three strands of B6 connect, read and describe data and graphs on disease and risk factors, reason carefully about correlation and cause, match answers to command words, and avoid the most common B6 errors.

This lesson draws together all three Assessment Objectives: AO1 (secure recall across the three B6 strands), AO2 (applying percentage-change calculations to data) and AO3 (interpreting graphs and evaluating correlation-versus-cause arguments in extended answers).

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How the B6 Topics Fit Together

Topic B6 is best seen as three strands of a single challenge — keeping people and the planet healthy.

flowchart TD
  A["Global challenges (B6)"] --> B["Human health"]
  A --> C["Feeding the population"]
  A --> D["Protecting the environment"]
  B --> B1["Communicable disease:<br/>pathogens, immunity,<br/>vaccines, antibiotics"]
  B --> B2["Non-communicable disease:<br/>risk factors, lifestyle,<br/>cardiovascular, cancer"]
  C --> C1["Selective breeding + GM crops"]
  C --> C2["Biotechnology + sustainable fishing"]
  D --> D1["Monitoring: indicator species<br/>+ sensors"]
  D --> D2["Maintaining: conservation,<br/>reforestation, less pollution"]

Notice how the strands connect: a virus (communicable) such as HPV can cause cancer (non-communicable); genetic engineering appears in both food (GM crops) and medicine (GM bacteria making human insulin); and sustainable farming and fishing link the food strand to the environment strand. Spotting these links is exactly the kind of synoptic thinking that lifts an answer.

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Reading Data and Graphs on Disease and Risk Factors

Much of B6 — especially non-communicable disease — is tested through data: risk-factor tables, scatter graphs and bar charts of disease rates. A reliable routine works for all of them:

1. Read the axes (or table headings) first — what is plotted against what, and in what units?
2. Describe the trend in words, using comparative language ("the disease rate rises as exposure increases").
3. Quote figures from the data to support what you say — a value at the start and at the end.
4. If asked to explain or judge cause, give the biology (a mechanism) and remember that correlation is not proof of cause.

Worked Example — describing and calculating from risk data

Consider this example set of readings for a lifestyle risk factor and the number of cases of a disease per thousand people:

Level of risk factor	Cases per 1000 people
None	5
Low	8
Medium	14
High	25

Describe the trend and quote figures. As the level of the risk factor increases, the number of cases increases, from $5$5 per $1000$1000 with none to $25$25 per $1000$1000 at the high level — a positive correlation.

Calculate the percentage increase from "none" to "high". Use the change divided by the starting value, times one hundred:

$\text{percentage increase} = \frac{25 - 5}{5} \times 100 = 400\%$percentage increase=525−5​×100=400%

So the high level is associated with cases 400% higher (five times as many) as no exposure.

Judge cause. This correlation alone does not prove the factor causes the disease — there could be a third factor, or coincidence. A causal conclusion also needs a plausible biological mechanism and the pattern to appear repeatedly in many studies.

Exam Tip: For a graph or table question, always describe, quote, then judge: describe the trend, quote a figure, and (if asked about cause) state that correlation does not prove cause — a mechanism and repeated evidence are needed too. This phrasing earns marks reliably.

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Correlation versus Cause: The Key Reasoning Skill

This idea runs through the whole health strand, so make it automatic.

• A correlation means two things change together (e.g. more smoking and more lung cancer).
• A correlation alone does not prove cause — there could be a third factor, or coincidence.
• Scientists accept a causal link only when there is a clear correlation, a plausible biological mechanism, and the result is found repeatedly in many studies.

Exam Tip: When a graph shows a risk factor "linked" to a disease and you are asked whether it proves cause, the safe answer is no — correlation does not prove cause; you also need a mechanism and repeated evidence.

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The Facts to Know Cold

Cover the right-hand column and test yourself.

Prompt	Answer
Definition of health	Physical, mental and social wellbeing, not merely absence of disease
Four types of pathogen	Bacteria, viruses, fungi, protists
How bacteria vs viruses make us ill	Bacteria reproduce fast + release toxins; viruses reproduce inside cells and damage them
Three white-blood-cell roles	Phagocytosis, antibodies (to antigens), antitoxins
What a vaccine contains	Dead/inactivated pathogen or its antigens
Antibiotics work on...	Bacteria only — not viruses (antivirals are used for viruses)
How resistance arises	Mutation to resistant bacteria survive and reproduce (natural selection)
Drugs from nature	Willow to aspirin; foxglove to digitalis; Penicillium to penicillin (Fleming)
Drug-testing order	Cells/tissues to animals to healthy volunteers to patients
Benign vs malignant	Benign stays put; malignant invades and spreads
Mycoprotein source	The fungus Fusarium (grown in a fermenter)
Air-pollution indicator	Lichens (present = clean air)
Clean vs polluted water indicators	Mayfly larvae = clean; sludgeworms = polluted

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Command Words You Will Meet in B6

Command word	What it asks for
State / Name / Give	A short fact, no explanation
Describe	Say what happens, in order, with no reasons
Explain	Give reasons why — use "because", "so that"
Compare	Give similarities and differences
Calculate	Work out a number — show working and give a unit
Suggest	Apply your knowledge to an unfamiliar context
Evaluate	Weigh advantages and disadvantages and reach a judgement

Exam Tip: B6 has many evaluate questions (e.g. on vaccination, GM crops or heart-disease treatments). An evaluate answer must give points on both sides and end with a conclusion or judgement.

Same topic, different command word

Students often lose marks by writing the wrong kind of answer — describing when asked to explain, or listing one side when asked to evaluate. The table below shows how the same piece of B6 knowledge is answered differently depending on the command word.