Health: The Ultimate Treasure
Health means much more than "not being sick." Discover how diseases spread, how vaccines protect you, and why antibiotics don't work on a common cold!
What is health, really?
Physical (your body), Mental (your mind/feelings), and Social (your relationships). All three matter together — a lonely student who eats well but has no friends isn't fully healthy either.
Ayurveda teaches that health comes from balance: following a daily routine (dinacharya) and seasonal routine (ritucharya), eating food suited to your body type (prakriti), regular exercise, cleanliness, restful sleep, and a calm mind — supported by yoga and meditation.
🎮 Sort it: symptom or sign?
A symptom is something you FEEL but can't always measure (like pain). A sign is something that CAN be seen or measured (like a fever reading on a thermometer).
Staying healthy & clean surroundings
🥗 3.2.1 Maintain a healthy lifestyle
Eat a balanced diet full of fruits, vegetables, and whole grains — and avoid processed, fatty, or sugary food and drinks. Stay physically active (outdoor play, walking, running, cycling, exercising). Limit screen time and spend more time in nature. Get enough sleep so your body and mind can rest and recover. Practise yoga or simple breathing exercises like pranayama. And say "NO" to harmful substances like tobacco, alcohol, and addictive drugs.
The book asks you to list good habits your parents/teachers encourage, and separately list habits that are NOT good for your health. Here's a model answer:
Good habits (parents/teachers encourage):
Not-so-good habits:
🌳 3.2.2 Keep the environment clean
Staying healthy isn't only about our own habits — our surroundings matter too! Clean air and water are important for our health. In cities, air pollution from vehicles and factories can cause problems like coughing or asthma.
The Air Quality Index (AQI) helps us know how clean (or polluted) the air is. A cleaner environment helps us stay healthy and feel better — while dirty, polluted surroundings (with stagnant water, garbage, flies and mosquitoes) make people fall sick more often.
The book shows Fig. 3.3(a) — a clean, well-maintained playground — and Fig. 3.3(b) — a polluted, dirty playground full of flies and mosquitoes near smoking factories.
Which playground would you like to play in, and why?
Even if we eat well and live in a clean place, we may not feel good if we are lonely or upset. Spending time with friends and family, talking, laughing, and having fun helps keep our minds healthy too — that's the social and mental side of health from section 1!
A Grade 8 student moved to a new school in another city. With no friends in his new environment and busy parents, he felt lonely. To cope, he spent more time on his phone and social media — but this made him feel worse. He stopped trying to make friends, had headaches, lost weight, and could not sleep well. A doctor advised less screen time and meeting a counsellor. The school counsellor arranged help to support him in making friends and improving his health.
Diseases: causes & types
A disease disrupts the normal working of the body or mind. There are two big categories:
| Type | Caused by | Spreads person-to-person? | Examples |
|---|---|---|---|
| Communicable | Pathogens (germs) | Yes | Typhoid, dengue, flu, chickenpox |
| Non-communicable | Lifestyle, diet, environment | No | Diabetes, asthma, cancer |
Bacteria, viruses, fungi, worms, or single-celled protozoa can ALL be pathogens. An insect that carries a pathogen from one person to another (like a mosquito) is called a vector.
The book's diagram shows SIX common routes a pathogen can take from an infected person to a healthy one: direct contact (like shaking hands), by air (coughing/sneezing), indirect contact (sharing things like towels or clothes), by food (contaminated food or water), mosquitoes/insects (vectors), and even the bite of a rabid animal (like a dog with rabies). Knowing the route helps you know exactly which precaution stops it!
Some non-communicable diseases are caused by a lack of specific nutrients in the diet — these are called deficiency diseases. Examples: scurvy (lack of vitamin C), anaemia (lack of iron), and goitre (lack of iodine). They aren't caused by pathogens, so they don't spread from person to person — eating a balanced diet is the best prevention!
Diseases such as cancer, diabetes, and asthma may often persist for a long time — more than 3 months — and are referred to as chronic diseases.
Diabetes is a common disease that is becoming more prevalent in adults as well as children. In fact, India now has one of the highest numbers of people with diabetes in the world. It often develops due to a combination of hormonal imbalances, unhealthy eating habits, lack of physical activity, and being overweight or obese, among other reasons.
The book asks you to find out the 3 most common lifestyle-related diseases in YOUR neighbourhood — by talking to a doctor, nurse, health worker, or family member, or checking trusted health websites/books — and fill in Table 3.2 with their signs/symptoms and suggested lifestyle changes. Here's a model filled-in table (your own neighbourhood survey might turn up different diseases for #4!):
| S. No. | Lifestyle-related disease | Signs & symptoms | Suggested lifestyle change(s) |
|---|---|---|---|
| 1 | Obesity | Excess body weight, tiredness, breathlessness on exertion | Eating a balanced diet and exercising regularly |
| 2 | Diabetes | Frequent urination, excessive thirst, weight loss, tiredness, slow healing of wounds | Balanced diet with less sugar, regular exercise, routine blood-sugar checks |
| 3 | High blood pressure | Headaches, dizziness, blurred vision (often no symptoms at all!) | Reduce salt/oil in diet, exercise regularly, manage stress, avoid tobacco & alcohol |
| 4 | Heart disease (student's own find) | Chest pain, breathlessness, fatigue on exertion | Balanced low-fat diet, regular exercise, no smoking, regular health check-ups |
🦟 How diseases spread — Table 3.1 (all 8 diseases from the book)
| Disease | Caused by | Site of infection | Symptoms | Spreads through |
|---|---|---|---|---|
| Common cold / flu | Virus | Respiratory tract | Nasal congestion & discharge, sore throat, fever, cough, body ache | Air (coughing/sneezing) |
| Chickenpox | Virus | Respiratory tract, skin | Mild fever, itchy skin, rashes, blisters | Air (respiratory tract), skin contact |
| Measles | Virus | Skin, respiratory tract | Fever, sore throat, reddish rashes on neck, ears & other skin | Air (respiratory tract), skin contact |
| Tuberculosis | Bacteria | Lungs | Cough, fever, fatigue, loss of appetite, night sweats | Air, close contact (lungs) |
| Hepatitis A | Virus | Liver | Fatigue, fever, loss of appetite, nausea, vomiting, jaundice, pain in upper right abdomen | Contaminated food/water (liver) |
| Cholera | Bacteria | Intestine | Diarrhoea and dehydration | Contaminated food/water (intestine) |
| Typhoid | Bacteria | Intestine | Headache, abdominal discomfort, fever, diarrhoea | Contaminated food/water (intestine) |
| Ascariasis (roundworms) | Worms | Intestine | Worms in stool, loss of appetite, poor growth, diarrhoea, weight loss, anaemia | Contaminated food/water (intestine) |
| Malaria | Protozoa | Skin, blood | High fever, profuse sweating, periodic chills | Mosquito bite (vector) — skin, blood |
| Dengue | Virus | Skin, blood | Fever, headache, muscle & joint pain, nausea | Mosquito bite (vector) — skin, blood |
Measles is a viral disease with fever, sore throat, and a reddish rash on the neck, ears and other parts of skin — prevented by isolation, covering mouth/nose, hygiene, and vaccination. Ascariasis (roundworms) is caused by worms living as parasites in the intestine, causing worms in stool, loss of appetite, poor growth, diarrhoea, weight loss and anaemia — prevented the same way as other water/food-borne diseases: hygiene, sanitation, and properly cooked food + boiled water.
Wash hands with soap and water, cover your mouth/nose when coughing or sneezing, wear a mask in crowded places, avoid sharing personal items like towels, and rest at home when you're unwell — this protects YOU and everyone around you!
Immunity & vaccines
Your body has a natural defence system called the immune system that fights off pathogens. This ability to resist disease is called immunity.
Vaccines contain weakened or dead pathogens (or harmless parts of them). They train your immune system to recognise and fight a germ before you ever get sick from it — this is called acquired immunity. The second time your body meets the same pathogen, it reacts much faster and stronger, because it "remembers" from before!
You may have gotten a tetanus injection after a cut or injury — it protects against infection by tetanus-causing bacteria. It contains an inactivated bacterial toxin (a harmless, "switched-off" version of the toxin), which helps your immune system develop protection without actually causing the disease. That's acquired immunity in action!
Vaccines protect people of all ages — from infants to the elderly — against many serious diseases. They help prevent illnesses and reduce the spread of infections, saving millions of lives every year. But remember: vaccines are preventive, not curative — they can stop a serious disease from happening in the first place, but they do NOT treat an infection someone already has. That's why getting vaccinated on time (before you're exposed) matters so much!
In the late 1700s, English doctor Edward Jenner noticed that milkmaids who caught the mild disease cowpox never seemed to catch the deadly disease smallpox.
Jenner's scientific method:
Long before modern vaccines, India had a traditional method called variolation, done by practitioners called teekedaars. Today, India is one of the world's LARGEST vaccine producers, supplying vaccines to countries around the globe — and Indian scientist Maharaj Kishan Bhan helped develop the Rotavirus vaccine that protects children from diarrhoea.
Kamal Ranadive was a pioneering Indian biomedical researcher. She studied how hormones and certain viruses are linked to cancer, helping improve its treatment and prevention. Her work also showed how tobacco, diet, and pollution can raise the risk of cancer — highlighting the importance of a healthy lifestyle for preventing non-communicable diseases like cancer!
Antibiotics & resistance
In 1928, scientist Alexander Fleming noticed that a mould growing (by accident!) on a forgotten petri dish was killing the bacteria around it. That mould led to penicillin — the world's first antibiotic.
A cold, cough, or flu is caused by a virus, not bacteria. Antibiotics only target special parts of BACTERIAL cells — so they simply can't touch a virus. Taking antibiotics for a viral illness doesn't help at all, and can even make bacteria elsewhere in your body develop antibiotic resistance — meaning that antibiotic stops working against them in the future!
🌍 Fig. 3.5(a): how antibiotic resistance spreads through the WHOLE community
Antibiotic resistance doesn't stay in one place — it travels through animals, food, and people, round and round:
🦠 Fig. 3.5(b): exactly HOW bacteria become antibiotic-resistant
Only take antibiotics when a doctor prescribes them, take the FULL course even if you feel better early, and never take them "just in case" for a viral illness. This keeps antibiotics working for everyone, for years to come.
Traditional medicine systems like Ayurveda, Siddha, and Unani have been used in India for many years to manage common health problems. They use natural substances like herbs, oils, and minerals for managing illnesses and promoting recovery, and focus on a healthy lifestyle and balanced diet. But while these systems can help with some conditions and everyday well-being, they may not be effective for all diseases and at all stages — so for serious or bacterial infections, modern medical treatment (like antibiotics, prescribed by a doctor) is still essential.
In Bhadrak district, Odisha, a community-led sanitation campaign helped more people build and use toilets. This significantly reduced open defecation, and improved child health, with fewer cases of diarrhoea and infections.
Every question from the book
Communicable: Cold and flu, Typhoid, Chickenpox (all caused by pathogens, all spread person-to-person)
Non-communicable: Diabetes, Asthma (lifestyle/environment-linked, don't spread person to person)
(b) ii and iii — Asthma and Diabetes. (Typhoid and Measles are both communicable, pathogen-caused diseases.)
(i) Immediate school action: Encourage sick students to stay home and rest, ask everyone to wear masks and cover their mouth/nose when coughing or sneezing, increase handwashing reminders, keep classrooms well-ventilated, and clean commonly-touched surfaces (desks, door handles) more often.
(ii) Responding kindly to a bench-mate with symptoms: Don't tease or avoid them meanly — gently suggest they tell a teacher and rest/see a doctor, offer to share notes so they don't fall behind, and be understanding rather than making them feel bad for being unwell.
(iii) Protecting yourself and others: Wash your hands often with soap and water, avoid touching your face, don't share food or water bottles, wear a mask if needed, and cover your own mouth/nose when you cough or sneeze too.
(i) Precautions before/during/after: Before — check with a doctor about anti-malarial medicine/advisories, pack mosquito repellent and nets. During — use mosquito repellent, wear long-sleeved clothes especially at dawn/dusk, sleep under a mosquito net, avoid areas with standing water. After — watch for symptoms like fever, chills and sweating for a couple of weeks, and see a doctor promptly if they appear.
(ii) Explaining to a sibling: Mosquito nets and repellents create a barrier so the mosquito that might be carrying the malaria parasite (a vector) can't bite us — "no bite means no malaria germ gets in!"
(iii) Ignoring advisories: Travellers could get bitten by infected mosquitoes and catch malaria themselves, feel very sick with high fever and chills, and could even unknowingly help the disease spread further if they get bitten again while infected.
(i) Talking to your uncle kindly: Share that you care about his health and want him around for a long time, gently mention how smoking harms the lungs and heart and raises cancer risk, and encourage him to find healthier ways to feel like he belongs — without judging or lecturing him harshly.
(ii) If a friend offers you a cigarette: Politely but firmly say "No thanks, I don't smoke" — you don't need an elaborate excuse. A true friend will respect your choice. You could also just walk away or change the topic.
(iii) How schools can help: Teach students about the real health effects of tobacco/alcohol/drugs, run awareness campaigns and posters, create a supportive environment where saying no is normal, and involve counsellors to support students facing peer pressure.
Vinita could ask: "Do antibiotics work against VIRUSES, like the flu or common cold?" or "What about diseases caused by protozoa, like malaria?" The truth is antibiotics ONLY work on bacteria — they do nothing against viruses or protozoa, so Saniya's claim is incorrect.
Highest: July, August, September (65 cases each). Lowest: January (10 cases).
July–September is India's monsoon season — heavy rain creates stagnant water pools, perfect mosquito breeding grounds, and warm humid weather speeds up their life cycle. That's exactly why the bulletin board fact said "Arrival of monsoon leads to increase in malaria and dengue cases"! Try the live bar graph below.
(iv) Preventive steps before the peak season: The community/government could clear or cover stagnant water (in drains, coolers, flowerpots, tyres, construction sites) before the rains arrive, fog or spray areas with mosquito larvicide, distribute mosquito nets and repellents in high-risk areas, run awareness drives about covering water tanks and removing standing water at home, and set up early fever-surveillance/health camps so dengue cases are caught and treated quickly once the season starts.
Hepatitis A, Poliomyelitis, and Cholera all spread through water contaminated by an infected person's excreta. Tuberculosis and Chickenpox do NOT spread this way — Tuberculosis spreads through the air (coughing, close contact with an infected person's lungs), and Chickenpox spreads through the air and direct skin contact, not water.
To reduce communicable diseases: "Wash your hands often!", "Cover your cough and sneeze!", "Don't share personal items like towels or water bottles!", "Get vaccinated on time!", and "Stay home and rest when you're unwell so you don't spread it to others."
To reduce non-communicable diseases: "Eat a balanced diet — go easy on junk food, oil and sugar!", "Stay active every day — play a sport or just move around!", "Limit screen time!", "Get enough sleep!", and "Say NO to tobacco, alcohol, and drugs!" A good campaign uses posters, fun activities, and peer discussions to make these messages stick.
Antibiotics only target special parts found in bacterial cells — a cold, cough, or flu is caused by a virus, which doesn't have those bacterial parts. So the antibiotic simply cannot act on it, and taking it won't help you get better. Worse, taking antibiotics unnecessarily can kill helpful "good bacteria" in your body and encourage antibiotic resistance to develop in other bacteria — making antibiotics less effective for everyone in the future, including you, when you truly need them for a bacterial infection.
The first time, your immune system has to "learn" to recognise the pathogen, so the response is slow. But it creates memory cells that remember that exact pathogen. Next time it shows up, your immune system recognises it instantly and fights back much faster and stronger — this is exactly how acquired immunity (and vaccines) work!
Discover, design & debate
Track your food, hygiene, exercise, sleep, screen time, and emotional state every day for at least a month. At the end, look back — do you notice patterns? Maybe you sleep worse on days with lots of screen time, or feel happier on days you exercised. A health diary helps you see the links between your habits and how you actually feel!
Read about these Indian scientists and their contributions to health and disease: Suniti Solomon (diagnosed India's first HIV cases and pioneered HIV/AIDS care and research in India), Asima Chatterjee (a pioneering chemist who developed anti-epileptic and anti-malarial drugs from plants), Yellapragada Subbarao (a biochemist whose work led to breakthrough treatments including methotrexate for cancer), and Mary Poonen Lukose (India's first woman surgeon-general, who greatly improved public healthcare and maternal/child health services in Travancore).
Smallpox — once a deadly disease that killed millions — was completely eradicated worldwide by 1980 through mass vaccination campaigns (like the 1965 global vaccine campaign you read about with Edward Jenner). Discover how this was done and why it worked, then debate: "Should everyone be required to get vaccinated to protect others?"
Learn the correct sequence of steps for cardiopulmonary resuscitation (CPR) on an adult in case someone's breathing suddenly stops, following current guidelines. This is best learned with your school inviting a doctor or trained professional to demonstrate a proper mock drill — CPR is a real, life-saving skill!
Invite a doctor to your school and discuss: malnutrition (when the body doesn't get the right balance of nutrients — too little OR too much), under-nutrition (not enough nutrients, leading to problems like being underweight or deficiency diseases), and over-nutrition (too many nutrients/calories, which can lead to obesity and lifestyle diseases like diabetes). Both extremes are forms of malnutrition!
If you could design a personal health card, what would you include? Think about things like: your blood group, any allergies, emergency contact numbers, past illnesses or vaccinations, and any ongoing medical conditions. Create your own health card and discuss it with your classmates — why is each piece of information useful in an emergency?
"Are there ill-effects of fast food on companion animals (like pet dogs and cats)?" Just like people, animals can be fed processed, fatty, or sugary "human" food by well-meaning owners.
Practice like the real exam
MCQ style (1 mark each)
(b) Alexander Fleming, in 1928.
(b) vector
(c) Iodine. (Scurvy = lack of Vitamin C; Anaemia = lack of Iron; Goitre = lack of Iodine.)
Short answer (2 marks)
A symptom is felt but not directly measured, e.g. a headache. A sign can be seen or measured, e.g. a fever reading of 103°F on a thermometer.
Longer answer (3 marks)
When antibiotics are used unnecessarily or not finished as a full course, some bacteria survive and can develop resistance to that antibiotic. These resistant bacteria multiply and can even pass their resistance to other bacteria. Over time, that antibiotic stops working against those bacteria for anyone — making future infections much harder to treat. This is why doctors stress using antibiotics only when truly needed, at the full prescribed dose.
Case study (4 marks)
(a) Cholera is caused by bacteria and spreads through contaminated water and food — exactly what happened when the flooding damaged the clean water supply.
(b) Boil all drinking water before use; maintain personal hygiene and good sanitary habits (and vaccination, where available).
(c) Communicable — it's caused by a pathogen (bacteria) and can spread from contaminated sources to many people, unlike non-communicable diseases which are linked to lifestyle, not germs.
You did it! 🎉
🏁 Chapter 3 of 7 · Term 1 Science · Prishita, Class 8