Health: The Ultimate Treasure
Chapter 3 · Curiosity — Science Textbook for Grade 8 · Complete Solutions
This page provides step-by-step, detailed answers to every in-text (Probe & Ponder, Activity reflection) question and every end-of-chapter exercise question from Chapter 3 — Health: The Ultimate Treasure (NCERT Curiosity, Grade 8). Diagrams are recreated for clarity wherever needed.
A
In-Text Questions
Probe and Ponder · Page 28
1. How does your body respond to an infection such as common cold?
Answer
When a cold virus enters the body, the immune system recognises it as a harmful pathogen. White blood cells attack and try to destroy the virus, while the body raises its temperature slightly (mild fever) to slow down viral growth. This immune response also causes symptoms such as a runny or blocked nose, sneezing, sore throat, and mild body ache — these are signs that the body is actively fighting the infection. After a few days, once the immune system gains the upper hand, the symptoms gradually subside and the person recovers.
2. We rarely see cases of smallpox or polio these days, but diseases like diabetes and heart problems are more common. Why?
Answer
Smallpox and polio are communicable diseases caused by pathogens (viruses). Through mass vaccination campaigns, public awareness, and improved sanitation, these diseases have been almost eradicated — smallpox was declared globally eradicated in 1980. On the other hand, diabetes and heart disease are non-communicable diseases linked to modern lifestyle factors such as eating processed and sugary food, reduced physical activity, stress, and longer life expectancy. As lifestyles have changed and people live longer, the occurrence of these lifestyle-related diseases has increased, even as infectious diseases have declined due to vaccines and hygiene.
3. Could climate change lead to new types of diseases?
Answer
Yes. Climate change can alter temperature and rainfall patterns, allowing disease-carrying vectors such as mosquitoes to survive and breed in new regions that were earlier too cold for them — expanding the spread of diseases like malaria and dengue. Rising temperatures, floods, and changing weather can also affect water and food safety, increase heat-related illnesses, and create conditions for new or re-emerging pathogens to thrive, potentially leading to new disease patterns.
4. How do emotions like stress or worry affect us and make us sick?
Answer
Prolonged stress or worry weakens the body's immune system, making it harder to fight infections. Stress can also lead to headaches, high blood pressure, poor sleep, loss of appetite or overeating, and difficulty concentrating. Since health includes mental and social well-being (not just physical health), chronic emotional stress can contribute to both physical illness (like ulcers or heart problems) and mental health issues such as anxiety and depression.
5. Why do some groups of people get affected more than others during disease outbreaks?
Answer
Some groups are more vulnerable due to factors such as weaker immunity (young children, elderly, or those with existing illnesses), poor access to clean water, sanitation, and healthcare, overcrowded living conditions, malnutrition, or lack of awareness about preventive measures and vaccination. People in such conditions are more easily exposed to pathogens and find it harder for their bodies to fight infections, so outbreaks affect them more severely.
Activity 3.1 — Let us Read · Page 29
Think and Reflect: What was the cause of the boy's health problems? How did his habits and surroundings affect his well-being?
Answer
The boy's health problems were caused by loneliness and lack of social connection after moving to a new city, combined with busy parents who could not give him enough attention. To cope with loneliness, he increased his phone and social media use, which made him feel worse instead of better — showing that excessive screen time does not solve emotional problems and can deepen isolation. This unhealthy coping habit led to physical symptoms (headaches, weight loss, poor sleep) and worsening mental health, since he stopped trying to make friends. This example shows that health is not just physical — his social isolation (social health) and stress (mental health) directly affected his physical health, proving that all three aspects of health (physical, mental, social) are interconnected.
In-text Bubble Question · Page 36
What will happen if I take excess amount of any of the minerals or vitamins?
Answer
Just as a deficiency of vitamins and minerals causes diseases (like scurvy, anaemia, or goitre), taking them in excess amounts can also be harmful and lead to a condition called toxicity (hypervitaminosis/over-nutrition). For example, excess Vitamin A can cause headaches, nausea, and liver damage; excess iron can damage organs; and excess sodium or sugar intake can contribute to high blood pressure or diabetes. This is why a balanced diet — with nutrients in the right proportion, neither too little nor too much — is recommended for good health, and supplements should only be taken under medical advice.
In-text Bubble Question · Page 35
Are diseases always caused by infections?
Answer
No. Diseases caused by pathogens (bacteria, viruses, fungi, worms, protozoa) are called communicable/infectious diseases and they spread from person to person. However, many diseases such as diabetes, cancer, asthma, and heart disease are non-communicable — they are not caused by infections but result from lifestyle, diet, hormonal imbalance, genetics, or environmental factors, and they do not spread from one person to another.
Activity 3.6 — Let us Read · Page 37
What do you infer from the Odisha (Bhadrak district) community sanitation campaign case study?
Answer
The case study shows that simple, low-cost community measures like building and using toilets can greatly reduce the spread of communicable diseases. By reducing open defecation, the contamination of soil, water, and food by disease-causing pathogens (such as those causing diarrhoea and other infections) was reduced. This directly improved child health in the community. It demonstrates that disease prevention is not always about medicines — improving sanitation, hygiene, and community awareness (public health measures) can be just as effective, and sometimes more sustainable, in controlling communicable diseases.
Activity 3.7 — Let us Infer · Page 41
Study the infographic (Fig. 3.5b). How do you think antibiotic resistance has been developed in bacterial pathogens? What precautions may be taken to reduce antibiotic resistance?
How resistance develops
- When antibiotics are used (especially unnecessarily, in wrong doses, or for an incomplete course), most bacteria are killed, but a few bacteria may have natural variations that make them resistant.
- These resistant bacteria survive the antibiotic treatment because the "good" sensitive bacteria (including helpful ones protecting the body) are killed along with the harmful ones, removing competition.
- The surviving resistant bacteria multiply rapidly and take over the population.
- Some resistant bacteria can even transfer their resistance genes to other bacteria, spreading resistance further and causing more widespread problems.
Precautions to reduce antibiotic resistance
- Take antibiotics only when prescribed by a qualified doctor — never self-medicate.
- Always complete the full prescribed dose and duration, even if symptoms improve early.
- Do not use antibiotics for viral infections (like cold or flu), since they are ineffective against viruses.
- Avoid using antibiotics indiscriminately in livestock and poultry farming.
- Maintain good hygiene and get vaccinated to reduce the need for antibiotics in the first place.
B
Exercise Questions (Keep the Curiosity Alive)
Question 1
Group the diseases shown in the images as communicable or non-communicable: Cold and flu, Typhoid, Diabetes, Asthma, Chickenpox.
Answer
Cold/flu, typhoid, and chickenpox are caused by pathogens (virus/bacteria) and spread from person to person, so they are communicable. Diabetes and asthma are linked to lifestyle, genetics, and environmental factors, do not spread between people, and are therefore non-communicable.
| Communicable Diseases | Non-Communicable Diseases |
|---|---|
| Cold and flu | Diabetes |
| Typhoid | Asthma |
| Chickenpox | — |
Question 2
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)
Answer
Correct option: (b) (ii) and (iii) — Asthma and Diabetes
Typhoid and Measles are caused by pathogens (bacteria and virus respectively) and spread from person to person, so they are communicable diseases. Asthma and Diabetes are not caused by pathogens — they are linked to lifestyle, genetic, and environmental factors — making them non-communicable diseases.
Typhoid and Measles are caused by pathogens (bacteria and virus respectively) and spread from person to person, so they are communicable diseases. Asthma and Diabetes are not caused by pathogens — they are linked to lifestyle, genetic, and environmental factors — making them non-communicable diseases.
Question 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 encourage sick students to stay home and rest until they recover; ensure students and staff wear masks and cover their mouth/nose while coughing or sneezing; promote frequent handwashing with soap; sanitise classrooms, desks, and commonly touched surfaces regularly; improve ventilation in classrooms; and inform parents and arrange medical advice/awareness sessions about flu prevention.
(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?
I would gently and kindly suggest that they inform the teacher and visit the school nurse or doctor, encourage them to rest at home and drink fluids, and offer to share notes or help them catch up on schoolwork later. I would maintain basic precautions like wearing a mask and washing my hands often, without making them feel isolated, judged, or unwelcome.
(iii) How can you protect yourself and others from getting infected in this situation?
Wash hands frequently with soap and water; avoid touching the face; wear a mask in crowded or close-contact situations; avoid sharing personal items like water bottles, towels, or handkerchiefs; maintain a healthy diet and adequate sleep to keep immunity strong; and cover my own mouth and nose if coughing or sneezing, and stay home if I fall sick.
Question 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: Consult a doctor for any preventive anti-malarial medication if recommended, pack mosquito repellents, mosquito nets, and full-sleeved clothing.
During: Use mosquito repellent creams/sprays, sleep under a mosquito net, wear long-sleeved clothes especially at dawn and dusk (when mosquitoes are most active), and avoid areas with stagnant water.
After: Monitor for symptoms like fever, chills, and sweating for a few weeks after returning, and consult a doctor immediately if any symptoms appear.
During: Use mosquito repellent creams/sprays, sleep under a mosquito net, wear long-sleeved clothes especially at dawn and dusk (when mosquitoes are most active), and avoid areas with stagnant water.
After: Monitor for symptoms like fever, chills, and sweating for a few weeks after returning, and consult a doctor immediately if any symptoms appear.
(ii) How can you explain the importance of mosquito nets or repellents to your sibling?
I would explain that malaria is spread by the bite of infected mosquitoes, so mosquito nets and repellents act as a barrier that stops the mosquitoes from biting us in the first place. Since malaria can cause high fever, severe sweating and chills, and can become serious if untreated, using nets and repellents is a simple way to stay protected without needing medicine.
(iii) What could happen if travellers ignore health advisories in such areas?
If health advisories are ignored, travellers risk getting bitten by infected mosquitoes and contracting malaria, which can cause high fever, severe weakness, and complications affecting organs if not treated promptly — in severe cases it can even be life-threatening. They may also unknowingly carry the infection back to their home city, contributing to its spread in a new area.
Question 5
Your uncle has started smoking just to fit in with his friends, even though smoking can seriously harm health and even cause death.
(i) What would you say to him to make him stop, without being rude?
I would calmly tell him that I care about his health and that smoking can seriously damage his lungs and heart, increase the risk of cancer, and reduce his lifespan. I would gently mention that true friends accept each other as they are, and that he doesn't need to harm his health just to feel accepted. I could also share facts and offer to support him if he wants to quit, perhaps suggesting he speak with a doctor.
(ii) What would you do if your friend offers you a cigarette at a party?
I would politely but firmly say no, explaining that I am not interested in smoking and care about my health. I would try to change the topic or move to a different activity, and avoid the pressure to fit in by reminding myself that real friends will respect my choice.
(iii) How can schools help prevent students from indulging in such harmful habits?
Schools can organise awareness sessions and workshops about the harmful effects of tobacco, alcohol, and drugs; invite doctors or counsellors to talk to students; promote peer-support and refusal-skills programmes; encourage healthy extracurricular activities like sports; ensure a strict no-smoking/no-substance policy on campus; and create a safe, open environment where students feel comfortable discussing peer pressure with teachers or counsellors.
Question 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?
Answer
Vinita could ask Saniya questions such as:
- "Do antibiotics work against viral infections like the common cold or flu, or only against bacteria?"
- "If antibiotics can cure any infection, why do doctors say there is no cure for diseases like dengue or COVID-19, which are caused by viruses?"
- "What happens to bacteria when antibiotics are used incorrectly or unnecessarily — could they develop resistance and stop responding to the antibiotic?"
- "If bacteria become resistant to antibiotics, would the antibiotic still be able to cure the infection?"
Question 7 — Numerical / Data Analysis
The table shows dengue cases reported in a hospital over one year. Make a bar graph (Y-axis: number of cases; X-axis: month) and analyse the data.
(i) Three months with highest dengue cases
From the data: $\text{July} = 65$, $\text{August} = 65$, $\text{September} = 65$ cases — these three months recorded the highest (and equal) number of dengue cases.
(ii) Month(s) with lowest cases
$\text{January} = 10$ cases — this is the lowest value recorded in the table, making January the month with the fewest dengue cases.
(iii) Environmental factors during peak months (July–September)
July to September corresponds to the monsoon season in most parts of India. Heavy rainfall leads to water accumulation in puddles, containers, coolers, tyres, and other places, creating ideal stagnant-water breeding grounds for the Aedes mosquito (the dengue vector). The warm and humid weather during this period also speeds up the mosquito's breeding cycle, leading to a sharp rise in dengue cases.
(iv) Preventive steps before the peak season
- Conduct community fogging and larvicide spraying drives before monsoon arrives.
- Ensure no stagnant water collects in coolers, flowerpots, tyres, or containers — empty and clean them weekly.
- Distribute mosquito nets and repellents to households, especially in high-risk areas.
- Run public awareness campaigns about covering water storage and wearing full-sleeved clothing.
- Improve drainage systems to prevent waterlogging in streets and open areas.
- Set up rapid diagnosis and treatment facilities at local health centres in anticipation of a rise in cases.
Question 8
Imagine you are in charge of a school health campaign. What key messages would you use to reduce communicable and non-communicable diseases?
For Communicable Diseases
- "Wash your hands often — soap and water keep germs away!"
- "Cover your cough and sneeze — protect your friends too."
- "Don't share personal items like towels, bottles, or combs."
- "Get vaccinated on time — prevention is better than cure."
- "Drink clean, boiled water and eat properly cooked food."
- "Eat a balanced diet — say no to junk and processed food."
- "Stay active — at least 30–60 minutes of play or exercise daily."
- "Limit screen time and spend more time outdoors."
- "Get enough sleep — your body and mind need rest to recover."
- "Say NO to tobacco, alcohol, and addictive substances."
- "Manage stress through yoga, meditation, and talking to someone you trust."
Question 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?
Answer
Antibiotics work by targeting specific structures or processes found in bacterial cells (such as their cell wall), which are different from human and viral structures. Since colds, coughs, and flu are caused by viruses, not bacteria, antibiotics have no target to act on and cannot kill or stop the virus. Taking antibiotics unnecessarily in such cases does not help cure the viral infection; instead, it can kill the helpful bacteria in our body and increase the chances of disease-causing bacteria developing antibiotic resistance, making future bacterial infections harder to treat. Hence, antibiotics should be avoided for viral infections and only used when prescribed by a doctor for bacterial infections.
Question 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.
Answer
Hepatitis A, Poliomyelitis, and Cholera may spread through water contaminated by the excreta of an infected person, since these pathogens are excreted in faeces and transmitted via the faecal-oral route when contaminated water is consumed.
Tuberculosis spreads mainly through air (droplets from coughing/sneezing of an infected person), and Chickenpox spreads through air and direct contact with skin lesions — neither spreads through contaminated drinking water.
Tuberculosis spreads mainly through air (droplets from coughing/sneezing of an infected person), and Chickenpox spreads through air and direct contact with skin lesions — neither spreads through contaminated drinking water.
Question 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?
Answer
During the first exposure to a pathogen, the immune system takes time to recognise it as foreign and produce the right defence cells/antibodies, so the response is slow and weak initially. However, after this first encounter, the immune system creates special "memory cells" that retain information about that specific pathogen.
When the same pathogen enters the body again, these memory cells recognise it immediately and trigger a much faster and stronger immune response, often destroying the pathogen before it can cause noticeable illness. This is the basic principle behind how acquired immunity and vaccination work — vaccines expose the body to a weakened or harmless form of the pathogen so that memory cells are formed in advance, ready to respond quickly if the real pathogen is encountered later.
When the same pathogen enters the body again, these memory cells recognise it immediately and trigger a much faster and stronger immune response, often destroying the pathogen before it can cause noticeable illness. This is the basic principle behind how acquired immunity and vaccination work — vaccines expose the body to a weakened or harmless form of the pathogen so that memory cells are formed in advance, ready to respond quickly if the real pathogen is encountered later.