CLASS 8 SCIENCE · CHAPTER 3 · STUDY NOTES
Health: The Ultimate Treasure
Understand health: the ultimate treasure through short explanations, labelled models and original practice. Read one topic, explain it in your own words, then check.
EXPLORE
Health includes body, mind and relationships
Explain why being free of fever is not the whole meaning of health.Three connected aspects
- Health
- Physical, mental and social well-being, rather than only the absence of disease.
Physical health concerns how your body works. Mental health includes thoughts and feelings. Social health includes supportive relationships and participation.
Feeling sad or worried sometimes does not make someone a failure. Support from trusted people matters, and a person with a long-term condition can still have a fulfilling life.
Take a moment. What do you think?
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Question
A student is physically well but feels isolated after changing schools. Which aspect of health needs support?
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Healthy habits need healthy surroundings
Connect a daily habit and a community condition with health.Personal and shared protection
- Hygiene
- Practices that help keep people and their surroundings clean.
- Sanitation
- Safe management of waste and conditions that help protect public health.
Varied nutritious food, activity, sleep, clean hands and supportive relationships help health. Tobacco and harmful substance use can damage it.
People also need safe water, cleaner air and waste collection. Good health is not only an individual choice; communities and public services matter.
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Question
A child washes their hands, but the local water supply is contaminated. Why are personal habits alone not enough?
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Feeling and measuring give different clues
Distinguish a symptom from a sign.Two kinds of clue
- Symptom
- A change that the person experiences, such as pain or dizziness.
- Sign
- A change that can be observed or measured, such as a rash or high temperature.
A person may describe a headache: that is a symptom. A thermometer can show high temperature: that is a sign. Together, clues help a health professional investigate.
One clue can have several possible causes. A diagram or symptom list cannot diagnose a person.
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Question
A student says their throat hurts, and a nurse measures a high temperature. Identify one symptom and one sign.
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Infections travel by specific routes
Match an infection route with a measure that interrupts it.Find the route to interrupt
- Pathogen
- A disease-causing organism or infectious agent.
- Vector
- An organism that can carry a pathogen between hosts.
Communicable diseases can spread between hosts. Examples include flu through respiratory spread, cholera through contaminated food or water, and malaria through infected mosquitoes.
The mosquito is a vector; the malaria-causing protozoan is the pathogen. Dengue is caused by a virus and is also transmitted by mosquitoes. Not all diseases use the same route.
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Question
Why does removing stagnant water help control a mosquito-borne disease rather than every disease equally?
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Not every disease is an infection
Distinguish disease spread from disease risk.Contact is not the cause
- Non-communicable disease
- A disease that does not spread between people like an infection.
- Deficiency disease
- A disease caused by a lack of a needed nutrient.
- Chronic condition
- A health condition that lasts for a long time and may need ongoing care.
Diabetes, asthma and many other long-term conditions do not spread through ordinary contact. Causes and risk factors can include genes, environment, nutrition and other factors. Do not blame every illness on a person’s habits.
A lack of vitamin C can cause scurvy; iodine deficiency can cause goitre. These are different from infections. Treatment and continuing care depend on the specific condition.
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Question
Can you catch diabetes by sharing a classroom with someone who has it?
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Vaccines prepare an immune response
Explain the role of immune memory without treating a vaccine as a cure.Prepare before a later encounter
- Immunity
- The body’s ability to defend itself against disease.
- Vaccine
- A preparation that helps train an immune response against a particular pathogen.
Vaccination presents a safe form, part or instruction related to a pathogen. The immune system responds and can develop memory, helping it respond more effectively to later exposure.
Vaccines help prevent illness or reduce its severity. They are not a general cure for someone who is already ill. Protection varies; the relevant health professional advises which vaccination is appropriate.
Let’s look a little closer.
Go deeper: A historical change
Jenner’s work helped establish vaccination against smallpox. A worldwide vaccination programme eventually led to smallpox eradication, officially declared by WHO in 1980. Earlier variolation carried serious risks and should not be confused with modern vaccination.
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Question
Why can a trained immune response act faster when it meets the same pathogen later?
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Resistance belongs to bacteria
Explain why surviving resistant bacteria can become more common.Watch which bacteria remain
- Susceptible
- These bacteria can be affected by this antibiotic.
- Resistant
- These bacteria can survive this antibiotic; survivors may multiply.
- Antibiotic
- A medicine that kills bacteria or stops their growth.
- Antibiotic resistance
- The ability of bacteria to survive an antibiotic that previously worked against them.
Antibiotics do not treat a viral cold. Use them only as prescribed, in the dose and duration advised by the health professional. Do not share or use leftover antibiotics.
Some bacteria may resist an antibiotic. When susceptible bacteria are removed, resistant survivors can multiply and spread. The bacteria become resistant, not the person.
Go deeper: Discovery and continuing care
Fleming observed in 1928 that a mould inhibited bacterial growth; this helped lead to penicillin. Preventing infections, safe prescribing and infection control all help preserve effective antibiotics. Long-term non-communicable conditions may need different treatments and ongoing support.
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Question
After treatment, some resistant bacteria survive. Why can their proportion increase?
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