13 marksCuriosity Grade 8, Chapter 3, Activity 3.6, page 37
What do you infer from the Odisha community sanitation campaign case study?
Hint. Note which kind of disease fell, and what was actually changed.
The case. 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 to infer. The chapter states it: simple steps like good sanitation can greatly reduce the spread of communicable diseases.
Why sanitation specifically. Look at Table 3.1. Cholera, typhoid, hepatitis A and ascariasis all spread through contaminated water and food, and the contamination comes from human waste reaching drinking water. Stop open defecation and you cut that route — which is exactly why diarrhoea cases fell.
Two further points worth drawing out.
It was community-led. One family building a toilet helps that family a little; the whole community doing it protects the shared water supply. Communicable disease is a collective problem, so prevention often has to be collective too.
No medicine was involved. No vaccine, no antibiotic — just infrastructure and changed habits. This is 'prevention is better than cure' demonstrated with evidence.
What the activity asks next. Find out about similar community campaigns in your own area, share them in class, and discuss their impact.
✦ Answer: that simple sanitation measures greatly reduce communicable disease — building and using toilets cut open defecation, which broke the contaminated-water route by which diarrhoea and infections spread, and it worked because the whole community acted together.
23 marksCuriosity Grade 8, Chapter 3, Section 3.5, page 37
What is immunity? Why do some people fall sick more often than others even when living in similar environments?
Hint. The chapter names both the ability and the system that provides it.
Immunity is the natural ability of our body to fight diseases.
The immune system is the special system in the body that carries this out — it helps fight against diseases.
Why people differ. The chapter raises exactly this puzzle: some people get sick more frequently than others although living in a similar environment. The answer is that immunity is not the same for everyone. It is affected by:
- Nutrition — poor diet weakens the body's defences
- Age — the very young and the elderly generally have weaker immunity
- Existing illness — a chronic disease leaves less capacity to fight a new infection
- Sleep, exercise and stress — the lifestyle factors of section 3.2, which is why that section comes before this one
- Previous exposure or vaccination — having met a pathogen before, or been vaccinated against it, gives acquired immunity
Why this matters for the whole chapter. It links the two halves. Section 3.2's advice about diet, sleep and exercise is not separate from section 3.5's discussion of infection — a healthy lifestyle is part of how you resist communicable disease.
✦ Answer: immunity is the body's natural ability to fight diseases, carried out by the immune system; people differ because immunity varies with nutrition, age, existing illness, sleep and stress, and previous exposure or vaccination.
34 marksCuriosity Grade 8, Chapter 3, Section 3.5, pages 37-38
What is a vaccine and how does it work? What is acquired immunity? How are vaccines made?
Hint. The key word is 'training' — a vaccine does not fight the germ for you.
What a vaccine does. It helps our body fight certain diseases by training the immune system to recognise and attack harmful germs. It does not attack the germ itself; it prepares your own defences in advance.
Acquired immunity. The protection developed after exposure to a pathogen or a vaccine — as opposed to the immunity you are born with. A vaccine gives you this protection without your having to catch the disease first, which is the whole point.
How vaccines are made. The chapter lists three approaches:
| Type | What it contains |
|---|
| Traditional | Weakened or dead pathogens (viruses or bacteria) |
| Component | Inactive or harmless parts of the pathogen |
| Newer | Instructions telling our own body cells to make a harmless part of the germ, which the immune system then learns to fight |
The worked example. A tetanus shot, often given after an injury, protects against infection by the tetanus-causing bacteria. It contains an inactivated bacterial toxin that helps the immune system develop protection without causing the disease.
The crucial limitation. Vaccines are preventive, not curative — they can help prevent serious disease before it happens, but they do not treat someone who is already sick.
And the social point. Getting vaccinated protects you and also the people around you, since a person who does not catch a disease cannot pass it on.
✦ Answer: a vaccine trains the immune system to recognise and attack a germ, giving acquired immunity — protection developed after exposure to a pathogen or vaccine — and may be made from weakened or dead pathogens, harmless parts of them, or instructions for our own cells to make such a part; vaccines are preventive, not curative.
44 marksCuriosity Grade 8, Chapter 3, Think like a scientist, page 38
How did Edward Jenner discover the first vaccine? Set out his work in the observation-hypothesis-experiment-result-application sequence the chapter uses.
Hint. The chapter lays this out as a worked example of investigation — the same skill Chapter 1 taught.
The background. Smallpox was a deadly disease that caused blisters and killed millions. A milder disease called cowpox, seen in cows, could also infect humans.
The sequence, as the chapter sets it out:
| Stage | What happened |
|---|
| Observation | Jenner observed that milkmaids who had cowpox did not catch smallpox — likely because the two viruses are related |
| Hypothesis | Content in the pus of cowpox blisters protected people from smallpox |
| Experimentation | He injected cowpox sap into a boy, who later showed no illness when exposed to smallpox |
| Results | People infected with cowpox sap were now resistant to smallpox |
| Application | Mass vaccination eventually helped eradicate smallpox worldwide |
When. In the late 1700s, by an English doctor. This led to the invention of the first vaccine.
What the graph shows. Countries reporting smallpox from 1950 to 1980, falling after the 1965 vaccine campaign until smallpox was eradicated in 1979 — the hypothesis, tested and then applied at world scale.
A note on the experiment itself. Deliberately exposing a child to smallpox to test a hypothesis would not be permitted today; modern medical research requires informed consent and ethical approval. The science was sound and the outcome saved millions of lives, but the method belongs to its era.
✦ Answer: Jenner observed that milkmaids who had had cowpox did not catch smallpox, hypothesised that something in cowpox blisters was protective, tested it by injecting cowpox sap into a boy who then resisted smallpox, and the application — mass vaccination — eradicated smallpox worldwide by 1979.
53 marksCuriosity Grade 8, Chapter 3, Our scientific heritage, page 38
What was variolation, and who were the teekedaars?
Hint. India had a protective practice against smallpox long before Jenner.
Variolation. A traditional Indian method to protect against smallpox, used long before modern vaccines. It involved using material from a smallpox sore to scratch the skin, creating a mild infection and thereby building immunity.
Teekedaars. The people who performed this practice were known as teekedaars.
The principle it shares with vaccination. Both work by giving the body a controlled, survivable encounter with a pathogen so that the immune system learns to recognise it — what the chapter calls acquired immunity. Variolation is, in that sense, the same insight arrived at much earlier.
The important difference — and it is a safety difference. Variolation used material from smallpox itself, so the induced infection was mild only if things went well; there was a real risk of causing the disease. Jenner's advance was to use cowpox, a related but far milder disease, which produced protection at much lower risk. Modern vaccines go further still, using weakened, dead, or harmless parts of a pathogen so that they cannot cause the disease at all.
✦ Answer: variolation was a traditional Indian practice of scratching the skin with material from a smallpox sore to induce a mild infection and build immunity, performed by practitioners called teekedaars — the same principle as vaccination, but riskier, since it used smallpox itself rather than a milder related disease.
63 marksCuriosity Grade 8, Chapter 3, Ever heard of… and Be a scientist, page 39
What is India's role in vaccine production? Who was Maharaj Kishan Bhan?
Hint. One of these is about scale, the other about one particular vaccine.
India's role. India is one of the world's largest vaccine producers. It manufactures vaccines on a massive scale and supplies them to many countries. Indian vaccine companies played a key role during the COVID-19 pandemic and continue to support global health efforts.
Why scale matters here. Vaccines only prevent disease if enough people actually receive them, so manufacturing capacity is itself a public-health contribution — particularly for countries that cannot produce their own.
Maharaj Kishan Bhan. A well-known Indian doctor and scientist. As Secretary of the Department of Biotechnology, he helped promote science and innovation in India. He played a key role in developing the Rotavirus vaccine, which protects children from diarrhoea. He believed in using research to create affordable healthcare, and made a large difference to India's health and biotechnology sectors.
Why the rotavirus vaccine matters for this chapter. Diarrhoea is exactly the kind of illness the Odisha sanitation campaign was reducing. Here the same problem is attacked from the other direction — sanitation blocks transmission, a vaccine prepares the immune system, and both together do more than either alone.
The word 'affordable'. A vaccine that exists but cannot be paid for protects nobody, which is why affordability was treated as part of the scientific goal rather than an afterthought.
✦ Answer: India is one of the world's largest vaccine producers, supplying many countries and playing a key role during COVID-19; Maharaj Kishan Bhan, a doctor and scientist and Secretary of the Department of Biotechnology, helped develop the Rotavirus vaccine protecting children from diarrhoea, and worked for affordable healthcare.
73 marksCuriosity Grade 8, Chapter 3, Section 3.5, page 39
Why does the chapter stress that vaccines are 'preventive, not curative'? What does it say about people who fear or doubt vaccines?
Hint. The distinction decides *when* a vaccine is any use.
Preventive, not curative. Vaccines help minimise serious diseases before they happen, but do not treat them once someone is already sick.
Why the distinction matters practically. It settles the timing. A vaccine is worth having before exposure — which is why childhood immunisation happens in healthy children, and why a tetanus shot is given promptly after an injury rather than after the illness develops. Once a disease has taken hold, the treatment is something else entirely: antibiotics for a bacterial infection, or supportive care.
Why it is worth doing at all. Vaccines are one of the most effective ways to protect people of all ages — from infants to the elderly — against many serious diseases. They prevent illnesses, reduce the spread of infections, and save millions of lives every year.
On doubt. The chapter acknowledges directly that some people may fear or doubt vaccines, and answers it with two points:
- Scientists and doctors carefully test them for safety before they are used
- Getting vaccinated not only protects you but also the people around you — since someone who does not catch a disease cannot pass it on, vaccination protects those who cannot be vaccinated themselves
✦ Answer: because a vaccine works only before infection — it prevents serious disease but cannot treat someone already ill — and on doubts the chapter answers that vaccines are carefully tested for safety and that being vaccinated protects the people around you as well as yourself.
Solutions written by the tuition.in editorial team and checked against NCERT Curiosity - Textbook of Science for Grade 8 (hecu103.pdf), Chapter 3 'Health: The Ultimate Treasure', pages 28-45, Reprint 2026-27. HAND-WRITTEN throughout. Page count verified against the printed contents page (hecu1ps.pdf p.18): 18 pages, 28-45, matching exactly. Covers the 5 'Probe and ponder' prompts (p.28), all 7 activities (3.1-3.7), every in-text section (3.1-3.5.1), both 'Our scientific heritage' boxes (Ayurveda; variolation and teekedaars), both 'Be a scientist' boxes (Kamal Ranadive; Maharaj Kishan Bhan), both 'Think like a scientist' boxes (Jenner; Fleming), the 'Ever heard of' box on India's vaccine production, the 11 numbered 'Keep the curiosity alive' exercises (pp.42-45) and the 5 'Discover, design, and debate' projects (p.45). ALL OF TABLE 3.1 TRANSCRIBED FROM THE PDF rather than from memory - 10 diseases with causal agent, site of infection, symptoms and preventive measures, in the book's own three groupings (air-spread: common cold and influenza, chickenpox, measles, tuberculosis; water- and food-spread: hepatitis A, cholera, typhoid, ascariasis; insect-transmitted: malaria, dengue). Exercise Q7's dengue figures were transcribed and re-read: Jan 10, Feb 12, Mar 15, Apr 18, May 22, Jun 40, Jul 65, Aug 65, Sep 65, Oct 30, Nov 30, Dec 20 - so the three peak months are July, August and September at 65 each and the lowest is January at 10, with the rise beginning in June and the fall in October, which matches the monsoon and is the basis of the answer to (iii). Exercise Q10 was answered by route of transmission using Table 3.1: hepatitis A, poliomyelitis and cholera spread by faecal contamination of water, while tuberculosis and chickenpox are airborne and do not. THREE POINTS OF DELIBERATE CAUTION. (1) The 'could climate change lead to NEW types of diseases' prompt is answered as changing WHERE, WHEN and HOW MUCH existing diseases occur, with the emergence of genuinely new diseases flagged as an open research question rather than asserted. (2) The CPR project answer gives the broad current sequence and India's emergency number 112, but states plainly that CPR is a practical skill that cannot be learnt from a written description, that guidelines are periodically revised, and that it must be learnt hands-on from a qualified instructor - which is what the book itself asks by suggesting a doctor demonstrate a mock drill. (3) The four Indian scientists in the reading project are given as starting points describing the FIELD each worked in, with the student told to verify and cite sources and to note disagreement between them, rather than being handed specific dates and claims to reproduce.. Questions are referenced from the NCERT textbook for identification.
