Health: The Ultimate Treasure — Class 8 Science
Curiosity · Chapter 3
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6- Mathematics
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- Space weighted by chapter size
- Charts from the book's own data
- Traps corrected
2- Mathematics
- Space weighted by chapter size
- Charts from the book's own data
- Traps corrected
- Space weighted by chapter size
- Charts from the book's own data
- Traps corrected
- Space weighted by chapter size
- Charts from the book's own data
- Traps corrected
Chapter summary
Key ideas & terms
- Health
- A state of complete physical, mental, and social well-being, not merely the absence of disease.
- Pathogen
- A disease-causing organism such as a bacterium, virus, fungus, protozoan, or worm.
- Communicable disease
- A disease caused by pathogens that can spread from one person to another, such as flu or typhoid.
- Non-communicable disease
- A disease linked to lifestyle, diet, or environment that does not spread between people, such as diabetes.
- Vaccine
- A preparation that trains the immune system to recognise and fight a germ, giving acquired immunity.
- Antibiotic resistance
- The ability of bacteria to survive and multiply despite treatment with an antibiotic that once killed them.
Extra questions & answers
How does the WHO define health?
As a state of complete physical, mental, and social well-being, and not merely the absence of disease.
What is the difference between a symptom and a sign?
A symptom is what a person feels, like pain or tiredness; a sign is something that can be seen or measured, like fever or a rash.
How do communicable and non-communicable diseases differ?
Communicable diseases are caused by pathogens and spread between people, while non-communicable diseases are linked to lifestyle, diet, or environment and do not spread.
Name four ways pathogens can spread.
Through air (coughing or sneezing), contaminated water or food, direct or indirect contact, and vectors such as mosquitoes and houseflies.
What is immunity and which body system provides it?
Immunity is the natural ability of the body to fight diseases, provided by the immune system.
How does a vaccine protect us?
It trains the immune system using weakened, dead, or harmless parts of a germ so the body can recognise and fight that germ later, giving acquired immunity.
Who discovered the first vaccine, and against which disease?
Edward Jenner, who showed that people infected with cowpox did not catch smallpox, leading to the smallpox vaccine.
Why do antibiotics not work against the common cold or flu?
These are caused by viruses, and antibiotics act only on bacteria by targeting parts of bacterial cells, not viruses.
What is antibiotic resistance and how can it be reduced?
It is when bacteria survive antibiotics that once killed them; it is reduced by using antibiotics only when prescribed, in the correct dose, and for the full duration.
Why is vaccination described as preventive and not curative?
Vaccines help prevent serious disease before it happens but do not treat an illness once a person is already sick.
Probe and ponder
How does your body respond to an infection such as common cold?
When a virus that causes common cold enters the body, the immune system reacts. White blood cells try to fight the virus and we get symptoms like sneezing, runny nose, sore throat, mild fever and cough. These symptoms are signs that the body is fighting the infection. Rest, warm fluids and good hygiene help the body recover in a few days.
We rarely see cases of smallpox or polio these days, but diseases like diabetes and heart problems are more common. Why?
Smallpox has been eradicated and polio has been greatly reduced by widespread vaccination, which gives acquired immunity. Diabetes and heart diseases are non-communicable diseases linked to lifestyle changes such as eating more processed, sugary and fatty foods, less physical activity, more screen time, obesity and stress. Because lifestyles have changed, these NCDs have become more common.
Could climate change lead to new types of diseases?
Yes. Changes in temperature and rainfall affect where vectors like mosquitoes can live and breed, so diseases like dengue and malaria can spread to new areas. Floods, heat and air pollution can also weaken health, affect water and food safety, and help some pathogens grow more easily.
How do emotions like stress or worry affect us and make us sick?
Health includes mental and social well-being. Constant stress, worry or loneliness can disturb sleep, reduce appetite, cause headaches, lower concentration and weaken immunity, making us more likely to fall sick. Support from family, friends, counsellors, relaxation, yoga and meditation helps keep the mind healthy.
Why do some groups of people get affected more than others during disease outbreaks?
Some groups are more vulnerable because of weaker immunity as in young children and elderly, poor nutrition, crowded or unhygienic surroundings, lack of clean water and air, less access to healthcare and vaccines, and underlying conditions like diabetes. Lifestyle and environment therefore affect risk.
Share your questions
Students can frame their own curiosity questions, for example: Why do we get fever during infection? How do vaccines work? Can exercise prevent diabetes? Why is handwashing important? Any relevant health-related question is acceptable.
Activity 3.1: Let us read
Think and Reflect: What was the cause of the boy's health problems? How did his habits and surroundings affect his well-being?
The boy felt lonely after moving to a new city with no friends and busy parents. Loneliness and social isolation affected his mental health. To cope he spent more time on phone and social media, which increased stress and reduced sleep, leading to headaches, weight loss and poor sleep. Lack of physical activity, social interaction and support made both his mental and physical health worse. Counselling, less screen time and help in making friends improved his well-being, showing health is physical, mental and social.
Activity 3.2: Let us list
List some good habits that your parents, teachers, or elders often encourage you to follow. How many of these are already a part of your daily routine? Which ones would you like to start following? Add to the list below: Keep yourself clean by maintaining personal hygiene. Eat a healthy and balanced diet. Exercise regularly. Make time to relax or meditate every day.
Good habits include maintaining personal hygiene by bathing, brushing teeth and washing hands, eating a balanced diet with fruits, vegetables and whole grains, exercising or playing outdoors daily, getting enough sleep, and relaxing or meditating. Students should tick which habits they already follow and choose one or two to adopt, such as daily exercise or meditation, and discuss with family and teachers.
Now, think about habits that are not good for your health. Add more to the list below: Spending too much time on mobile phones or other digital screens. Eating fast food and other junk food every day. Sleeping very late or not getting enough sleep. Skipping meals, especially breakfast.
Unhealthy habits include excessive screen time, eating fast food and sugary drinks daily, sleeping late or not getting enough sleep, skipping breakfast, not washing hands, staying indoors all day, and using tobacco or alcohol. Avoiding these and replacing them with healthy routines protects both body and mind.
Activity 3.3: Let us compare
Look at Fig. 3.3a and Fig. 3.3b. Which playground would you like to play in, and why?
Most children would prefer the playground in Fig. 3.3a because it is clean, green, well-maintained and pleasant, whereas Fig. 3.3b is dirty, littered, polluted and has flies and mosquitoes. A clean environment reduces risk of infections and helps us breathe better and feel happier.
Have you ever found it hard to breathe in a place with a lot of smoke or dust?
Yes, in smoky or dusty places the air quality is poor. Air pollution from vehicles, factories and burning can irritate the nose and lungs and cause coughing or breathing difficulty and can trigger asthma. The Air Quality Index helps know how clean the air is. Clean air and water and clean surroundings are essential for health. Social health also matters, so spending time with friends and family in a clean environment keeps the mind healthy too.
Activity 3.4: Let us find out
Grade 8 students listed some common communicable diseases in Table 3.1 during a community campaign and a library search.
Table 3.1 summarises diseases spread through air, through contaminated water and food, and through insect vectors, with their causal agents, site of infection, symptoms and prevention. It helps understand how pathogens spread.
Check the information listed by referring to books, trusted websites, or asking your science teacher. Add any missing details.
Students should verify the table entries with teacher or trusted sources. All listed information is correct: common cold, influenza, chickenpox, measles and tuberculosis spread through air; hepatitis A, cholera, typhoid and ascariasis spread through contaminated water and food; malaria and dengue are transmitted by mosquitoes. Any additional local disease can be added.
Study the table and think about what simple steps can help prevent each disease.
General prevention includes keeping self and surroundings clean, practising daily hygiene, washing hands with soap, covering mouth and nose while coughing or sneezing, wearing masks in crowded places, not sharing personal items, keeping food and water clean by eating properly cooked food and drinking boiled water, using mosquito nets and repellents, wearing long-sleeved clothes, avoiding stagnant water, isolating patients when needed and getting vaccinated where vaccines are available.
Activity 3.5: Let us survey
Find out the three most common lifestyle-related diseases in your neighbourhood
Students can survey the neighbourhood. Common examples are obesity, diabetes and high blood pressure. In many areas, heart disease, asthma and joint problems are also reported. The exact three will vary by locality.
Talk to a doctor, nurse, health worker or even a family member who knows about health and what kind of lifestyle changes can help prevent or manage these diseases.
Healthcare workers advise balanced diet with less oil, sugar and salt, more fruits, vegetables and whole grains, regular physical activity, maintaining healthy weight, adequate sleep, limiting screen time, managing stress through yoga and meditation, and saying no to tobacco and alcohol. Regular check-ups and timely treatment are also important.
You can also consult trusted health websites, books, teachers and doctors.
Cross-check information from NCERT, WHO and other reliable health sources and teachers to ensure advice is correct before filling the table.
Fill in Table 3.2 and learn more about lifestyle-related diseases. Table 3.2: Non-communicable diseases S. No. Name of common lifestyle-related diseases Signs and symptoms Suggested lifestyle change(s) 1. Obesity Eating a balanced diet and exercising regularly 2. Diabetes Frequent urination Excessive thirst Weight loss Tiredness Slow healing 3. High blood pressure 4. ............................ ............................ ............................
Example completion: 1. Obesity - signs: excess weight, breathlessness, tiredness - lifestyle: balanced diet, regular exercise, less junk food. 2. Diabetes - signs: frequent urination, excessive thirst, weight loss, tiredness, slow wound healing - lifestyle: control sugar and oil, regular exercise, maintain weight. 3. High blood pressure - signs: headache, dizziness, chest discomfort often no clear symptoms - lifestyle: low salt diet, regular exercise, stress management, avoid tobacco. 4. Could be Heart disease or Asthma - signs: for heart disease breathlessness, chest pain; for asthma wheezing - lifestyle: healthy diet, exercise, avoid smoking and pollution.
Activity 3.6: Let us read
Odisha — community-led sanitation campaign In Bhadrak district, Odisha, a community sanitation campaign helped more people build and use toilets. This reduced open defecation significantly, and improved child health, with fewer cases of diarrhoea and infections. What do you infer from this case study?
The case shows that simple public health steps like good sanitation, building and using toilets and keeping surroundings clean can greatly reduce spread of communicable diseases that spread through contaminated water and food. Community participation improves health, especially for children.
Find about such community campaigns held in your location. Share in your class and discuss with your peers about the impact of such initiatives.
Students can look for Swachh Bharat Mission, Fit India Movement, handwashing drives, vaccination camps or local toilet construction drives in their area and share how these campaigns reduced infections, improved hygiene and raised awareness.
Activity 3.7: Let us infer
Study the infographic given in Fig. 3.5b. How do you think the antibiotic resistance has been developed in bacterial pathogens? What precautions may be taken to reduce antibiotic resistance?
Antibiotic resistance develops when antibiotics are used without need, in wrong doses or for incomplete duration, or given unnecessarily to livestock. Antibiotics kill sensitive bacteria but a few resistant bacteria survive, multiply and can transfer resistance to other bacteria. Resistant bacteria then spread through people, hospitals, food, water, soil and manure. Precautions: use antibiotics only when prescribed by a doctor, take correct dose for full duration, do not demand antibiotics for viral illnesses like cold, do not give antibiotics to cattle without veterinary advice, maintain hygiene and vaccination to reduce need for antibiotics.
Keep the curiosity alive
1. Group the diseases shown in the images as communicable or non-communicable. Cold and flu Typhoid Diabetes Asthma Chickenpox
Communicable diseases which spread from person to person via pathogens: Cold and flu, Typhoid, Chickenpox. Non-communicable diseases which do not spread and are linked to lifestyle, diet or environment: Diabetes, Asthma.
2. Diseases can be broadly grouped into communicable and non-communicable diseases. From the options given below, identify the non-communicable diseases. (i) Typhoid (ii) Asthma (iii) Diabetes (iv) Measles (a) (i) and (ii) (b) (ii) and (iii) (c) (i) and (iv) (d) (ii) and (iv)
Correct option is (b) (ii) and (iii). Asthma and Diabetes are non-communicable. Typhoid and Measles are communicable diseases caused by pathogens.
3. There is a flu outbreak in your school. Several classmates are absent, while some are still coming to school coughing and sneezing. (i) What immediate actions should the school take to prevent further spread?
The school should ensure sick students stay home, inform parents, improve ventilation, arrange handwashing facilities, encourage covering mouth and nose and wearing masks, regular cleaning of classrooms and common surfaces, and arrange health check-up and awareness on hygiene.
3. There is a flu outbreak in your school. Several classmates are absent, while some are still coming to school coughing and sneezing. (ii) If your classmate, who shares the bench with you, starts showing symptoms of the flu, how can you respond in a considerate way without being rude or hurtful?
Speak kindly and privately, suggest they inform the teacher and go home to rest, offer to share notes later, avoid stigma, encourage them to cover mouth when coughing and wash hands, and help maintain distance politely.
3. There is a flu outbreak in your school. Several classmates are absent, while some are still coming to school coughing and sneezing. (iii) How can you protect yourself and others from getting infected in this situation?
Wash hands frequently with soap, avoid sharing personal items like towels and water bottles, cover mouth and nose while coughing or sneezing, wear a mask in crowded classrooms, keep surroundings clean, eat nutritious food, get adequate sleep and stay home if you develop symptoms.
4. Your family is planning to travel to another city where malaria is prevalent. (i) What precautions should you take before, during, and after the trip?
Before trip: consult doctor about preventive measures, pack mosquito nets and repellents and long-sleeved clothes. During trip: use nets and repellents, wear covering clothes, avoid stagnant water areas, keep doors and windows screened. After trip: watch for symptoms like high fever with chills and sweating and consult doctor promptly if they appear.
4. Your family is planning to travel to another city where malaria is prevalent. (ii) How can you explain the importance of mosquito nets or repellents to your sibling?
Explain that malaria is caused by a protozoan spread by mosquito bites. Nets and repellents keep mosquitoes away while sleeping or playing, so germs cannot enter the blood. It is a simple, safe way to avoid painful fever and medicine.
4. Your family is planning to travel to another city where malaria is prevalent. (iii) What could happen if travellers ignore health advisories in such areas?
Ignoring advisories increases risk of getting malaria, leading to high fever, chills, need for hospital care, and spread to others via mosquitoes. It can also cause severe illness, especially in children.
5. Your uncle has started smoking just to fit in with his friends, even though it is well known that smoking can seriously harm health and even cause death. (i) What would you say to him to make him stop, without being rude?
Talk respectfully, express care, share facts that tobacco increases risk of cancer, heart disease and lung problems, explain that true friends respect healthy choices, and suggest healthier ways to be social, offering help like family support or counselling.
5. Your uncle has started smoking just to fit in with his friends, even though it is well known that smoking can seriously harm health and even cause death. (ii) What would you do if your friend offers you a cigarette at a party?
Politely but firmly say no, explain you care about health and do not want to start a harmful habit, suggest alternative fun activities, and stay with friends who respect your decision. If pressure continues, leave the situation and talk to a trusted adult.
5. Your uncle has started smoking just to fit in with his friends, even though it is well known that smoking can seriously harm health and even cause death. (iii) How can schools help prevent students from indulging in such harmful habits?
Schools can provide health education, counselling, awareness campaigns, poster competitions, involve parents, enforce tobacco-free campus, promote sports, yoga and peer support groups to build confidence to say no.
6. Saniya claims to her friend Vinita that “Antibiotics can cure any infection, so we don’t need to worry about diseases.” What question(s) can Vinita ask her to help Saniya understand that her statement is incorrect?
Vinita can ask: Do antibiotics work against viruses that cause cold, flu and chickenpox? What are viruses, bacteria and protozoa? Why do doctors not prescribe antibiotics for viral infections? What is antibiotic resistance and what happens if we misuse antibiotics? This helps realise antibiotics work only against bacterial infections and do not cure all diseases, and misuse makes them ineffective.
7. The following table contains information about the number of dengue cases reported in a hospital over a period of one year: S. No. 1 2 3 4 5 6 Month January February March April May June No. of dengue cases 10 12 15 18 22 40 S. No. 7 8 9 10 11 12 Month July August September October November December No. of dengue cases 65 65 65 30 30 20 Make a bar graph of the number of cases on the Y-axis and the month on the X-axis. Critically analyse your findings and answer the following: (i) In which three months were the dengue cases highest?
On the bar graph the heights correspond to the given numbers. The three highest months are July, August and September, each with 65 cases.
7. The following table contains information about the number of dengue cases reported in a hospital over a period of one year: Make a bar graph of the number of cases on the Y-axis and the month on the X-axis. Critically analyse your findings and answer the following: (ii) In which month(s) were the cases lowest?
The lowest case count is in January with 10 cases, followed by February with 12. So January has the lowest burden.
7. The following table contains information about the number of dengue cases reported in a hospital over a period of one year: Make a bar graph of the number of cases on the Y-axis and the month on the X-axis. Critically analyse your findings and answer the following: (iii) What natural or environmental factors during the peak months might contribute to the increase in dengue cases?
Peak during July-September coincides with monsoon. Rainfall creates stagnant water in containers, coolers and pits where Aedes mosquitoes breed. Higher humidity and moderate temperature also help mosquito growth, increasing transmission.
7. The following table contains information about the number of dengue cases reported in a hospital over a period of one year: Make a bar graph of the number of cases on the Y-axis and the month on the X-axis. Critically analyse your findings and answer the following: (iv) Suggest a few preventive steps that the community or government can take before the peak season to reduce the spread of dengue.
Before monsoon, community and government can clean and cover water storage, remove stagnant water, conduct fogging and larva control, distribute mosquito nets and repellents, run awareness campaigns on wearing long-sleeved clothes and keeping surroundings clean, and strengthen hospital preparedness.
8. Imagine you are in charge of a school health campaign. What key messages would you use to reduce communicable and non-communicable diseases?
Key messages: For communicable diseases: wash hands with soap, keep food and water clean and drink boiled water, cover mouth while coughing, wear masks when needed, do not share personal items, stay home when sick, get vaccinated, use mosquito nets and keep surroundings clean. For non-communicable diseases: eat balanced diet with less oil, sugar and salt, exercise daily, limit screen time, get enough sleep, manage stress with yoga and meditation, say no to tobacco, alcohol and drugs, and go for regular health check-ups.
9. It is recommended that we should not take an antibiotic for a viral infection like a cold, a cough, or flu. Can you provide the possible reason for this recommendation?
Antibiotics kill bacteria by targeting parts of bacterial cells. They have no effect on viruses. Cold, cough and flu are caused by viruses, so antibiotics will not cure them, may delay proper care and promote antibiotic resistance while killing helpful bacteria.
10. Which disease(s) among the following may spread if drinking water gets contaminated by the excreta from an infected person? Hepatitis A, Tuberculosis, Poliomyelitis, Cholera, Chickenpox.
Diseases that spread through contaminated water and food via the faecal-oral route are Hepatitis A, Poliomyelitis and Cholera. Tuberculosis spreads mainly through air and Chickenpox spreads through air and direct contact, not through water contaminated with excreta.
11. When our body encounters a pathogen for the first time, the immune response is generally low but on exposure to the same pathogen again, the immune response by the body is much more compared to the first exposure. Why is it so?
On first exposure the immune system takes time to recognise the pathogen and produce specific antibodies and memory cells, so response is slow and low. Memory cells remain in the body. On second exposure the memory cells quickly recognise the same pathogen and produce a faster, stronger and larger immune response, which is the basis of acquired immunity and vaccination.
Discover, design, and debate
Students maintain a health diary for at least a month to track food, hygiene, exercise, sleep, screen time, and emotional state.
Maintain a daily table with columns for date, meals, handwashing, bath, exercise time, hours of sleep, screen time, and mood. At the end of the week review patterns, note improvements such as more vegetables or less screen time, and set small goals. Sharing in class helps learn from peers.
Read about Indian scientists like Suniti Solomon, Asima Chatterjee, Yellapragada Subbarao, Mary Poonen Lukose for their contributions in the field of health and diseases.
Suniti Solomon pioneered HIV research and awareness in India, Asima Chatterjee developed medicines from plants for malaria and other diseases, Yellapragada Subbarao discovered important drugs and vitamins including folic acid and work on cancer drugs, Mary Poonen Lukose was a pioneering physician and leader in public health. Reading about them inspires interest in health research.
The deadly disease smallpox was eradicated by vaccination. Discover how this was done and why it worked. Debate whether everyone should be required to get vaccinated to protect others.
Smallpox was eradicated by global mass vaccination led by WHO. Edward Jenner’s vaccine trained immunity using related cowpox virus. Widespread coverage created herd immunity so the virus had no hosts and disappeared by 1979. Debate points: required vaccination protects community and vulnerable people but must balance individual choice, safety testing and awareness. Evidence shows vaccines are safe and benefits outweigh risks.
According to current guidelines, learn the correct sequence of steps for performing cardiopulmonary resuscitation (CPR) on an adult in case of sudden stoppage of breathing. School may invite a doctor or a professional to demonstrate a mock drill.
Basic steps: check responsiveness and breathing, call for help and emergency services, place person on firm surface, give 30 chest compressions at centre of chest followed by 2 rescue breaths if trained, continue until help arrives or breathing returns, use AED if available. Students should learn only under trained medical supervision through a mock drill.
Invite a doctor to the school. Students may be encouraged to interact with the doctor on the issues of malnutrition, under-nutrition, and over-nutrition.
Prepare questions on what is a balanced diet, why deficiency diseases like anaemia and goitre occur, risks of junk food leading to obesity, importance of clean water and exercise. Note doctor’s advice on eating diverse foods, maintaining hygiene and regular check-ups.
If you are given an opportunity to create a health card, what all would you like to include in it. Create your own health card and have discussion about it.
A health card can include name, age, height, weight, BMI, blood group, vaccination record, allergies, vision and dental check dates, diet and exercise habits, sleep hours, and remarks by doctor. It helps track growth and health over time and reminds to follow healthy habits.
Have a debate on ‘Are there ill-effects of fast food on companion animals?
For the motion: fast food high in oil, salt and sugar can cause obesity, diabetes, digestive problems and heart issues in pets like dogs and cats, similar to humans. Against: occasional small treats may not harm if balanced with proper pet food and exercise. Conclusion: pets need species-specific balanced nutrition, and fast food should be avoided for them.