You are viewing a free preview of this lesson.
Subscribe to unlock all 8 lessons in this course and every other course on LearningBro.
Topic B6 of OCR Gateway Combined Science A is named Global challenges because it turns the biology you have already met towards three of the largest problems the world faces: keeping people healthy, feeding a growing population, and looking after the environment everything depends on. This opening lesson begins the health strand with a question that sounds simple but is not — what does it really mean to be healthy? — before sorting the diseases that threaten health into two great families: communicable (infectious) diseases that can be passed on, and non-communicable diseases that cannot. Fixing these definitions and categories now will make every later lesson on pathogens, immunity, vaccination and lifestyle disease much easier to follow.
By the end of this lesson you should be able to define health as more than the absence of disease, tell communicable diseases apart from non-communicable ones with examples, explain how conditions can interact so that one disease makes another more likely, and outline the main factors that shape a person's health.
This lesson develops AO1 (understanding health, disease categories and the factors that affect health) and AO3 (reasoning about how diseases interact and which factors raise risk).
It is tempting to treat health as simply "not being ill", but the definition used widely is broader and far more useful:
Health is a state of physical, mental and social wellbeing, not merely the absence of disease.
Breaking that down into its three parts:
A person can have no diagnosed disease at all and still be unhealthy — for instance someone who is severely isolated, anxious or living in poor housing. Equally, a person with a well-managed long-term condition, such as controlled diabetes, may enjoy good overall wellbeing. Recognising all three dimensions is the first big idea of B6.
Exam Tip: If a question asks you to "define health", the marks reward the whole definition — physical, mental and social wellbeing, plus the phrase "not merely the absence of disease". Writing only "not being ill" throws away most of the marks.
A disease is a condition that stops part of the body working properly. Diseases fall into two main categories.
| Category | What it means | Can it be passed between people? | Examples |
|---|---|---|---|
| Communicable (infectious) | Caused by a pathogen (a disease-causing microorganism) | Yes — it can spread from person to person, or from another organism | Measles, influenza, HIV, tuberculosis, malaria, food poisoning |
| Non-communicable | Not caused by a pathogen; usually develops slowly | No — it cannot be caught or passed on | Coronary heart disease, most cancers, type 2 diabetes, asthma |
The word communicable shares its root with "communicate": these diseases can be communicated — passed on — from one host to the next. The thing that causes them is a pathogen: a bacterium, virus, fungus or protist, which you will study closely in the next lesson.
Non-communicable diseases are not caused by a pathogen and cannot spread. They tend to develop over a long time and are strongly linked to risk factors such as diet, exercise, smoking and inherited genes; you will meet them in detail later in the topic.
Exam Tip: A very common trap is to assume "infectious means bacteria and viruses only". Pathogens also include fungi (such as athlete's foot) and protists (such as the malaria parasite). And note that a disease being communicable tells you it is caused by a pathogen, but says nothing about how serious it is.
Diseases do not occur in neat isolation — having one condition can make a person more vulnerable to others. This idea of interactions between diseases is required by the specification, so learn a few clear examples.
Worked examples of interacting diseases:
The lesson from all of these is that the body is a connected system: a problem in one part rarely stays contained, which is one reason preventing disease in the first place matters so much.
Whether a person stays healthy depends on far more than luck. The main factors include:
These factors interact too. Poverty, for instance, can mean a poorer diet, more stress, worse housing and greater exposure to pathogens all at once — which is why health is so strongly tied to a person's wider circumstances.
Exam Tip: When a question asks for "factors that affect health", give a range (diet, stress, life situation, exposure to pathogens) rather than several versions of the same idea. Examiners reward breadth, not repetition.
Disease does not only affect the individual who is ill; it also carries a wider cost to society and the economy:
This is one reason why prevention — stopping disease before it starts — is such an important idea in B6: keeping people healthy reduces suffering and the burden on health services and the wider economy.
Exam Tip: A question may ask why governments invest in prevention (such as vaccination or healthy-eating campaigns). A strong answer is that prevention cuts both the human cost (illness and suffering) and the financial cost of treating widespread disease.
The mix of diseases affecting people is not the same everywhere, and OCR expects you to appreciate this in broad, qualitative terms — you do not need to memorise any figures.
These patterns can shift over time: as a country develops clean water, sanitation and vaccination, the burden tends to move from communicable towards non-communicable disease. That is why improving basic conditions — clean water, sanitation, vaccination and nutrition — has such a large effect on health worldwide.
An important idea, and one that examiners like to test, is that the factors affecting health do not act one at a time — they combine, and often reinforce one another. A single risk factor rarely tells the whole story. Consider someone living in poor, overcrowded housing with little money for fresh food. Straight away several factors are stacking up: a poorer diet (weakening the body and immune system), more exposure to pathogens (crowding makes communicable disease spread more easily), higher stress, and often less access to healthcare. Each factor on its own raises the risk of ill health a little; together they raise it a great deal. This is why health is so strongly tied to a person's wider circumstances, and why measures that improve those circumstances — better housing, clean water, income, education — can improve health on several fronts at once.
The reverse is also true and worth remembering: a protective factor such as a balanced diet, regular exercise and a safe, supportive home can lower the risk of both communicable and non-communicable disease at the same time. When you are asked why one group of people is healthier than another, look for several interacting factors rather than settling on a single cause.
Exam Tip: If a question asks you to explain why one population has more ill health than another, do not stop at one factor. The best answers identify several factors that act together — for example poor diet and overcrowding and limited healthcare — and explain how each adds to the risk. Naming the interaction is what lifts the answer.
| Misconception | The correct idea |
|---|---|
| "Health just means not being ill" | Health is physical, mental and social wellbeing, not merely the absence of disease |
| "All diseases can be caught" | Only communicable diseases spread; non-communicable diseases cannot be passed on |
| "Mental illness is not a real health problem" | Mental wellbeing is part of health; conditions such as depression are genuine illnesses |
| "Infectious diseases are only caused by bacteria and viruses" | Pathogens also include fungi and protists |
| "One disease has no effect on any other" | Diseases interact — a weak immune system leads to more infections; HPV can lead to cervical cancer |
A student writes: "Health means having no diseases in your body." Explain why this definition is incomplete, and give a better one.
The student's version covers only physical health, and even then it is narrow. The accepted definition is broader: health is a state of physical, mental and social wellbeing, and is not merely the absence of disease. The student's answer misses mental wellbeing (someone with depression is unwell even with no infection) and social wellbeing (isolation or poor housing damage health), and it also ignores that a person can manage a long-term condition and still be well overall. A better answer therefore states all three dimensions and the "not merely the absence of disease" phrase — that combination is what earns full marks.
Question (6 marks): Explain what is meant by health, and describe the difference between communicable and non-communicable diseases. Use examples.
Mid-band response: "Health means being well and not having a disease. Communicable diseases can be passed from person to person, like flu. Non-communicable diseases cannot be passed on, like heart disease."
Examiner-style commentary: This earns marks for the basic distinction between the two disease types with one example each. It is held back by an incomplete definition of health ("not having a disease" misses the wellbeing dimensions) and by giving no cause for either category. To climb a band, give the full health definition and state that communicable diseases are caused by pathogens.
Stronger response: "Health is a state of physical, mental and social wellbeing, not just the absence of disease. Communicable (infectious) diseases are caused by pathogens and can spread between people — for example measles, which is caused by a virus. Non-communicable diseases are not caused by pathogens and cannot be passed on; they often develop slowly and are linked to lifestyle, for example coronary heart disease."
Examiner-style commentary: A clear, accurate answer with the full definition of health, the cause of each disease category, and a correctly classified example of each. To reach the top band, add that diseases can interact and give an example of that interaction.
Top-band response: "Health is a state of physical, mental and social wellbeing, and is not merely the absence of disease — a person can be free of any diagnosed illness yet be unhealthy because of poor mental or social wellbeing. Communicable diseases are caused by pathogens (microorganisms such as bacteria, viruses, fungi or protists) and can be passed on from one host to another; an example is measles, caused by a virus. Non-communicable diseases are not caused by pathogens, cannot be spread, and tend to develop over a long time in response to risk factors such as diet and smoking; an example is coronary heart disease. Importantly, the two categories can interact: infection with certain HPV viruses (communicable) can lead to cervical cancer (non-communicable), and a disease that weakens the immune system makes a person more vulnerable to further infections."
Examiner-style commentary: Full marks. The answer gives the complete definition of health with the wellbeing dimensions, defines and exemplifies both disease categories with their causes, and — crucially — shows that diseases interact, with a precise example linking the two categories. This is exactly the breadth and accuracy the top band requires.
This content is aligned with OCR Gateway Combined Science A (J250), Topic B6 Global challenges. Refer to the official OCR specification for exact wording.