(a) A person complains of persistent itching in the groin region and scalp. The person also shows dry and scal

Question

Q. (a) A person complains of persistent itching in the groin region and scalp. The person also shows dry and scaly lesions on skin, nails, etc.

(i) Identify the disease.

(ii) Name its two causative agents.

(iii) Mention its mode of transmission.

(OR)

(b) A girl develops sneezing, watery eyes and difficulty in breathing every time she visits a flower garden.

(i) Identify the condition.

(ii) Name the immune component responsible for this condition.

(iii) Name the chemical released.

(iv) State one medicine used to treat such a condition.

CBSECBSE Class XII Board 2026Subjective· 2mImportance★★★★★

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Part (a)Concept understanding — Disease Transmission Modes

Let’s begin with something you already know. When someone in your family catches a cold, you instinctively avoid sharing their glass or sitting too close. That instinct is your brain recognising that something — a disease — can travel from one person to another. The how of that travel is what we call disease transmission modes.

In everyday language, a transmission mode is simply the route a germ takes to leave an infected person and reach a healthy one. Think of it as the germ’s travel plan. If the germ cannot travel, it cannot cause new infections. So understanding these routes is the first step in stopping outbreaks — whether it’s a common flu or a more serious epidemic.

The two big families: Direct and Indirect transmission

The NCERT textbook (Class XII, Biology, Chapter 8 — Human Health and Disease) divides transmission into two main categories. This is the standard classification you need to remember.

1. Direct Transmission — The germ moves straight from the infected person to the healthy person, with no intermediate object or living being involved. This can happen through:

Physical contact: Touching, shaking hands, kissing, or sexual contact. Diseases like the common cold, scabies, and sexually transmitted infections (e.g., syphilis, HIV) spread this way.
Droplet infection: When an infected person coughs, sneezes, or even talks, tiny droplets of saliva or mucus fly out. If you are within about a metre, you can inhale them. This is how influenza, the common cold, and COVID-19 spread.
Direct exposure to infected tissue or blood: For example, a needle-stick injury in a hospital, or a mother passing an infection to her baby during pregnancy (congenital transmission).

Note

Direct transmission is often the easiest to interrupt. Simple actions — like maintaining distance, wearing a mask, or washing hands — break the chain because the germ has no vehicle to ride on.

2. Indirect Transmission — Here, the germ needs a middleman to reach a new host. The middleman can be:

A vehicle: This is a non-living thing that carries the germ. Common vehicles include:
- Air: Dust particles or droplet nuclei (the dried remnants of droplets) can float for hours. Measles and tuberculosis spread through air.
- Water: Contaminated drinking water spreads cholera, typhoid, and hepatitis A.
- Food: Improperly cooked or stored food can carry salmonella or E. coli.
- Fomites: Inanimate objects like door handles, towels, syringes, or surgical instruments. Hepatitis B can spread through contaminated needles.
A vector: This is a living organism — usually an insect or animal — that carries the germ from one host to another. The vector itself is not infected (or is only incidentally infected). Classic examples:
- Mosquitoes: Female Anopheles mosquito transmits malaria; Aedes mosquito transmits dengue and chikungunya.
- Fleas: Rat fleas transmit the plague bacterium.
- Ticks: Spread Lyme disease.

Important

The key difference between a vehicle and a vector is that a vehicle is non-living, while a vector is a living creature. Both are intermediate agents — the germ does not jump directly from person to person.

Why this matters beyond biology

For a commerce or humanities student, the importance of transmission modes is not just medical — it is social and economic. Think about it:

If a disease spreads through water (like cholera), the solution is not a vaccine alone — it is clean water supply, sanitation infrastructure, and public awareness campaigns. That is a government policy and budget issue.
If a disease spreads through vectors (like malaria), the solution involves mosquito nets, insecticide spraying, and urban planning to eliminate stagnant water. That is a logistics and community management problem.
If a disease spreads through direct contact (like HIV), the solution involves education, behaviour change, and stigma reduction — which is a social science challenge.

In short, the mode of transmission determines the type of intervention needed. That is why public health officials always ask: “How is this disease spreading?” before they decide what to do.

A quick summary for revision …

Part (b)Concept understanding — Health Effects

Health Effects — A First Look

Think about the last time you drank water from a roadside stall during summer. Your mind probably weighed two things: the immediate thirst, and the vague worry about whether the water was clean. That worry — that something in the environment might harm your body — is exactly what "health effects" means.

In simple terms, health effects are the changes — good or bad — that happen to your body and mind when you are exposed to something in your surroundings. That "something" could be polluted air, contaminated food, loud noise, stress at work, or even a new medicine. The key idea is that your environment and your health are not separate; they are constantly interacting.

The precise meaning

The NCERT textbook (Class 12, Business Studies, Chapter 12 — Consumer Protection) introduces health effects in the context of consumer awareness. When you buy a product or use a service, you have a right to know whether it will harm you. Health effects, therefore, refer to the physical or mental consequences that arise from using a product, consuming a food item, or living in a particular environment.

These effects can be:

Immediate — like a headache from a chemical smell, or food poisoning from stale food.
Long-term — like lung disease from years of breathing polluted air, or hearing loss from constant loud music.
Direct — like a burn from a faulty appliance.
Indirect — like stress and anxiety caused by unsafe living conditions.

Important

Health effects are not just about illness. They also include positive effects — for example, the health benefit of drinking clean water or using a well-designed ergonomic chair. The term is neutral; it simply describes the outcome of an exposure.

Why it matters for a commerce/humanities student

You might think health effects belong only in biology or medicine. But in commerce and humanities, they are central to consumer protection, business ethics, and public policy.

Consider a company that sells packaged food. If the food contains a harmful preservative, the health effect on consumers could be serious — and the company faces legal action, loss of reputation, and financial penalties. That is why the Consumer Protection Act, 2019, gives you the right to safety — meaning products must not cause harm under normal use.

Similarly, in economics, health effects are part of externalities. A factory that pollutes a river creates a negative health effect for people downstream — but the factory does not pay for that harm. Understanding health effects helps you see why governments regulate industries and why consumers need protection.

A few key points to remember

Health effects can be physical (like a rash, cough, or injury) or mental (like anxiety, depression, or stress).
They can arise from products (food, medicines, electronics), services (healthcare, transport), or environmental factors (air, water, noise). …

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Ringworm — a fungal infection caused by Microsporum/Trichophyton, spread by contact/fomites.
Allergy — IgE antibodies act on mast cells, which release histamine; treated with anti-histamines.

Part (a)

The skin, especially warm, moist folds like the groin and scalp, is a favoured site for dermatophytic fungi. Persistent itching together with dry, scaly lesions on the skin and nails is the classic picture of Ringworm — one of the most common fungal diseases in humans.

(i) Disease: Ringworm (dermatophytosis).
(ii) Two causative agents: Microsporum and Trichophyton (the genus Epidermophyton also causes it). These fungi grow on keratin of skin, hair and nails.
(iii) Mode of transmission: mainly by contact —
- Direct contact with an infected person, animal, or with soil, and …

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Same / Similar Concept — real previous-year questions on the same or a closely similar concept, not this exact question.

Showing the 12 most recent of 24 on this concept.

CBSE 2026Set 57/3/11 markMCQ
$Q. Some statements regarding drugs and alcohol are given below :$
(i) Adolescents are more vulnerable to peer pressure.
(ii) Drug addiction leads to increased tolerance level of the receptors present in our body.
(iii) Alcohol affects the central nervous system.
(iv) Excessive use of drugs helps to increase energy.
(v) Anabolic steroids decrease aggressiveness. Choose the option with correct statement(s). (A) Statements (i),
(iv) and
(v) are correct (B) Statements (i),
(ii) and
(iii) are correct (C) Only statements
(i) and
(v) are correct (D) Only statement
(iii) is correct
›Reveal solutionSolution

Only statements (i), (ii), and (iii) are factually correct; statements (iv) and (v) are false.

Let’s look at each statement one by one, because this question tests not just memory but a clear understanding of how drugs and alcohol actually work in the body.

Statement (i) — Adolescents are more vulnerable to peer pressure. This is widely accepted. The teenage brain is still developing, especially the prefrontal cortex responsible for impulse control and long-term decision-making. At the same time, social belonging becomes intensely important. That combination makes adolescents genuinely more susceptible to peer influence, including pressure to try drugs or alcohol. So this statement is correct.

Statement (ii) — Drug addiction leads to increased tolerance level of the receptors present in our body. This is a precise and accurate point. With repeated use of many drugs, the body adapts. Receptors on nerve cells become less sensitive or reduce in number, so the user needs a larger dose to feel the same effect. That is exactly what tolerance means — it is a physiological change, not just a psychological one. So this statement is correct.

Statement (iii) — Alcohol affects the central nervous system. Absolutely. Alcohol is a central nervous system depressant. It slows down brain activity, impairs coordination, judgment, and reaction time, and in large amounts can lead to unconsciousness or even respiratory failure. This is one of the most basic facts about alcohol. So this statement is correct. …
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CBSE 2026Set A1 markMCQ
$Q. Which of the following diseases is/are transmitted by insect vectors?$
(a) Typhoid
(b) Malaria
(c) Filaria
(d) Both (B) and (C)
›Reveal solutionSolution

Malaria and filariasis are insect (mosquito) transmitted; typhoid is spread by contaminated food and water.

Malaria is transmitted by the female Anopheles mosquito, and filariasis (elephantiasis) is transmitted by the female Culex mosquito — both are insect vectors. Typhoid, caused by Salmonella typhi, is transmitted through food and water contaminated with …

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CBSE 2026Set ANNUAL1 mark
$Q. “Smoking causes oxygen deficiency in human body”. Justify the statement.$
›Reveal solutionSolution

Carbon monoxide in cigarette smoke binds haemoglobin more strongly than oxygen, reducing oxygen transport — so smoking causes oxygen deficiency.

Tobacco smoke contains carbon monoxide (CO) and nicotine. Haemoglobin, the oxygen-carrying pigment of blood, has a much higher affinity for CO than for oxygen (about 200 times). When a person smokes, CO binds haemoglobin to form stable carboxyhaemoglobin, so that much less haemoglobin is available to bind and transport oxygen.

…

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CBSE 2026Set ANNUAL1 mark
$Q. Write True or False. Cocaine is obtained from the leaves of the Erythroxylum coca and acts as a stimulant on the central nervous system.$
›Reveal solutionSolution

True — cocaine comes from the coca plant (Erythroxylum coca) and is a CNS stimulant.

In the CBSE/NCERT Human Health and Disease chapter (drugs and alcohol abuse), cocaine is extracted from the leaves of Erythroxylum coca, native to South America. It interferes with dopamine transport in the brain and acts as a powerful **stimulant …

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CBSE 2025Set ANNUAL1 mark
$Q. Name two diseases whose spread can be controlled by the eradication of Aedes mosquito.$
›Reveal solutionSolution

The Aedes mosquito is the vector for several viral diseases, notably dengue and chikungunya, so controlling its population directly limits their spread.

The Aedes mosquito acts as the vector transmitting several important viral diseases to humans, including dengue fever and chikungunya (it can also transmit Zika virus and yellow fever). Since these viral diseases spread only through the bite of an infected Aedes mosquito, eliminating its breeding sites (stagnant/clean standing water) and controlling its population is an …

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CBSE 2024Set 57/2/11 markMCQ
$Q. The vector for dengue fever is : (A) Female Aedes mosquito (B) Female Anopheles mosquito (C) Male Aedes mosquito (D) Female Culex mosquito$
›Reveal solutionSolution
Dengue fever is transmitted by the bite of an infected female Aedes mosquito (primarily Aedes aegypti), which requires a blood meal for egg development. The answer is (A).

Why vectors matter in disease transmission

A vector is an organism that transmits a pathogen from one host to another without suffering from the disease itself. For many viral diseases, mosquitoes serve as vectors because the pathogen replicates in the mosquito's body and is passed on when the mosquito feeds on blood.

The key biological detail: only female mosquitoes bite and feed on blood. Males feed on plant nectar and do not require blood meals. Females need the protein from blood to develop their eggs, which is why they are the disease vectors.

Identifying the dengue vector

Different mosquito genera transmit different diseases, and this specificity is crucial for public health control measures.

Aedes mosquitoes are the primary vectors for dengue fever. The species Aedes aegypti (and to a lesser extent Aedes albopictus) transmit the dengue virus when an infected female bites a human. These mosquitoes are recognizable by their distinctive black-and-white striped legs and body, and they typically bite during the day, especially in the early morning and before dusk.

Anopheles mosquitoes transmit malaria, not dengue. The Plasmodium parasite that causes malaria requires Anopheles as its vector. …
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CBSE 2024Set 57/3/11 markMCQ
$Q. (A) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A). (B) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A). (C) Assertion (A) is true, but Reason (R) is false. (D) Assertion (A) is false, but Reason (R) is true. Assertion (A) : The chronic use of alcohol by a person leads to cirrhosis. Reason (R) : Alcohol addiction at times becomes the cause of mental and financial distress to the entire family of the addicted person.$
›Reveal solutionSolution
Assertion (A) is true because chronic alcohol use damages the liver, leading to cirrhosis. Reason (R) is also true as alcohol addiction causes significant mental and financial distress to families. However, Reason (R) does not explain the biological mechanism behind Assertion (A). Therefore, both statements are true, but R is not the correct explanation for A.

When tackling Assertion-Reason questions, the strategy is always two-fold:

Independently evaluate each statement: Determine if Assertion (A) is true or false, and if Reason (R) is true or false.

Check for explanatory power: If both (A) and (R) are true, then determine if Reason (R) provides a correct explanation for Assertion (A). Does R answer "why" A is true?

Let's apply this approach to the given statements.

Evaluating Assertion (A): "The chronic use of alcohol by a person leads to cirrhosis."

Cirrhosis is a severe and irreversible scarring of the liver, which impairs its ability to function. The liver is the primary organ responsible for metabolizing alcohol. Chronic and excessive alcohol consumption overwhelms the liver's capacity to process alcohol and its toxic byproducts, leading to inflammation (alcoholic hepatitis) and eventually the destruction of liver cells, which are replaced by fibrous scar tissue. This process is known as cirrhosis.

Therefore, Assertion (A) is a factually correct statement.

Evaluating Reason (R): "Alcohol addiction at times becomes the cause of mental and financial distress to the entire family of the addicted person."

Alcohol addiction is a complex disease with far-reaching consequences beyond the individual. It often leads to strained relationships, emotional instability, neglect of responsibilities, and significant financial burdens due to the cost of alcohol, lost employment, and potential medical expenses. These factors invariably cause immense mental and financial distress to the family members who are directly affected by the addicted person's behaviour and circumstances.

Therefore, Reason (R) is also a factually correct statement.

Determining if Reason (R) explains Assertion (A): …
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CBSE 2024Set GG1 markMCQ
$Q. The vector of Dengue (Break bone) fever is:$
(a) Anopheles
(b) Culex
(c) Aedes
(d) None of these
›Reveal solutionSolution

Dengue is spread by the Aedes mosquito, so the answer is (c).

Concept. Many diseases have a specific insect vector. Matching the pathogen to its vector is important: malaria — Anopheles; filariasis — Culex; dengue and chikungunya — Aedes.

…

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CBSE 2023Set TERM21 markMCQ
$Q. A disease which can easily transmit from one person to another is called$
(a) Non-infectious disease
(b) Infectious disease
(c) Viral disease
(d) Bacterial disease
›Reveal solutionSolution

A disease that spreads from an infected person to a healthy person is called an infectious (communicable) disease.

Diseases are broadly grouped into non-infectious (e.g. cancer, allergies) and infectious diseases. Infectious diseases are caused by pathogens such as bacteria, viruses, fungi, protozoans and helminths, and these pathogens can be transmitted from an infected host to a healthy person directly (contact, air, water) or through vectors, which is why such diseases are also called …

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CBSE 2023Set ANNUAL1 markMCQ
$Q. What is a droplet infection?$
(a) syphilis
(b) tetanus
(c) typhoid
(d) pneumonia
›Reveal solutionSolution

Pneumonia is a droplet infection.

A droplet infection spreads when an infected person coughs or sneezes, releasing tiny droplets carrying the pathogen that a healthy person then inhales. Pneumonia (caused by Streptococcus pneumoniae or Haemophilus influenzae) spreads this way. In contrast, syphilis is a sexually transmitted disease, teta …

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CBSE 2022Set ANNUAL1 markMCQ
$Q. The Pathogen of elephantiasis is -$
(a) Amoeba
(b) Ascaris
(c) Filarial worm
(d) Plasmodium
›Reveal solutionSolution

Elephantiasis is lymphatic filariasis, caused by filarial worms (Wuchereria bancrofti / W. malayi).

Elephantiasis (filariasis) is a chronic disease caused by filarial worms, chiefly Wuchereria bancrofti and W. malayi. These thread-like helminths live in the lymphatic vessels, and are transmitted by the bite of female Culex mosquitoes. Chronic inflammation and blockage of lymph vessels lead to gross swelling of the affected par …

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CBSE 2022Set ANNUAL1 markMCQ
$Q. Which fever could be confirmed by Widal test ?$
(a) Malaria
(b) Dengue
(c) Corona
(d) Typhoid
›Reveal solutionSolution

Widal is an antibody-agglutination test that confirms typhoid fever.

Typhoid fever is caused by the bacterium Salmonella typhi. The Widal test is a serological test that detects agglutinating antibodies (against the O and H antigens of Salmonella) in the patient's serum; a rising titre confirms typhoid.

…

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Q.(a) A person complains of persistent itching in the groin region and scalp. The person also shows dry and scaly lesions on skin, nails, etc.

Part (a)

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