Chapter 7: Human Health and Disease Application Questions | biology Class 12 CBSE

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Chapter 7: Human Health and Disease Application Questions | biology Class 12 CBSE | ByteNotes.in

Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 1

Applied Concept

A 10-year-old child returns from school with dry, scaly, intensely itchy patches on the scalp. The family doctor suspects a fungal infection. With reference to the chapter, identify the disease, name the causative fungi and suggest two preventive measures.

The disease is ringworm (tinea capitis when on scalp), caused by fungi belonging to the genera Microsporum, Trichophyton and Epidermophyton; heat and moisture in skin folds promote fungal growth, but scalp infection is also common.
The infection is likely acquired from soil, or by sharing towels, combs or clothing with an infected person; the child may have used a classmate's comb or towel.
Preventive measures include avoiding sharing personal items such as combs, towels and clothes with others, maintaining personal hygiene (keeping the body clean and dry), and treating infected individuals promptly to prevent community spread.

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Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 2

Applied Concept

A patient returning from a tropical area develops recurring high fever with chills every three to four days. Blood smear examination reveals ring-shaped forms inside RBCs. With reference to the chapter, identify the disease, causative organism and explain why the fever is periodic.

The disease is malaria, caused by Plasmodium (specifically the periodic fever pattern and RBC involvement are characteristic); if the most severe form, it is caused by Plasmodium falciparum (malignant malaria).
Plasmodium invades red blood cells, replicates within them and causes their synchronised rupture; on rupture, haemozoin—a toxic substance—is released into the bloodstream, triggering each bout of chills and high fever.
The fever recurs every three to four days because the parasite's erythrocytic cycle (multiplication and RBC rupture) is synchronised; each cycle of mass RBC rupture releases haemozoin simultaneously, producing the characteristic periodic fever pattern.

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Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 3

Applied Concept

In a school canteen, several students develop stomach pain, constipation and blood-streaked stools after consuming food. The school doctor suspects amoebiasis. Explain how the infection spread and suggest measures to prevent future outbreaks.

Amoebiasis is caused by Entamoeba histolytica, a protozoan parasite of the large intestine; the infection spreads through food and water contaminated by faecal matter—houseflies act as mechanical carriers transmitting the parasite from faeces to food.
In the canteen scenario, the food was likely prepared or stored under unhygienic conditions allowing housefly contamination, or the drinking water source was contaminated by faecal matter from infected individuals.
Preventive measures include maintaining strict food hygiene (covering food, preventing fly access), using safe drinking water (boiled or treated), proper disposal of excreta and sewage, regular disinfection of the kitchen and enforcing handwashing protocols for food handlers.

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Application Question

Easy difficulty • Concept in a practical situation

Easy

Question 4

Applied Concept

A newborn baby is at risk of certain infections because its own immune system is not yet mature. With reference to the chapter, explain how the mother's body provides passive protection to the baby, giving two specific mechanisms.

During pregnancy, the mother transfers antibodies to the developing foetus through the placenta; these maternal antibodies provide passive immunity to the newborn against infections the mother has already encountered.
After birth, the mother secretes colostrum—a yellowish fluid during the initial days of lactation—which is rich in IgA antibodies that protect the newborn's gut from infectious agents.
Both mechanisms constitute passive immunity because the baby receives ready-made antibodies produced by the mother rather than producing its own; this protection is temporary but critical until the baby's own immune system matures.

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Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 5

Applied Concept

A patient is brought to a hospital after a venomous snakebite. The doctor immediately administers an injection rather than waiting for the patient's immune system to respond. With reference to the chapter, explain what this injection contains and the principle behind this treatment.

The injection contains preformed antibodies (anti-venom) produced against the specific snake venom; this is an example of passive immunisation where ready-made antibodies are directly transferred to protect the body.
Active immunity (producing one's own antibodies) is too slow—it takes days to weeks to reach effective levels; snake venom can be fatal within hours, making passive immunisation with preformed antibodies the only effective immediate option.
Similarly, in tetanus infections, antitoxin (antibodies against the tetanus toxin) is injected to provide immediate neutralisation; while the protection is short-lived, it buys critical time when rapid immune response is essential.

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Application Question

Hard difficulty • Concept in a practical situation

Hard

Question 6

Applied Concept

A 30-year-old man who underwent a kidney transplant is prescribed immuno-suppressant drugs for life. With reference to the chapter, explain why these drugs are necessary and what would happen if they were stopped.

The immune system distinguishes 'self' from 'non-self' using cell surface antigens; T-lymphocytes recognise the transplanted kidney's antigens as non-self and mount a cell-mediated immune response attempting to reject the graft.
Immuno-suppressant drugs dampen the T-lymphocyte-mediated immune attack on the transplanted organ, preventing rejection and allowing the body to accept the new kidney.
If the drugs are stopped, T-lymphocytes will resume their attack on the transplanted kidney, leading to graft rejection; the patient's immune system would destroy the donated organ, ultimately causing kidney failure.

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Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 7

Applied Concept

A woman who moves to a new city starts sneezing uncontrollably and her eyes become watery whenever she walks through a particular park. When she leaves the park, symptoms disappear. With reference to the chapter, explain the biological mechanism causing these symptoms.

The woman is experiencing an allergic reaction; an allergen (likely pollen from plants in the park) is triggering an exaggerated response by her immune system producing IgE antibodies specific to that allergen.
On exposure to pollen, IgE antibodies on mast cells trigger these cells to release chemicals—histamine and serotonin—into surrounding tissues, causing symptoms such as sneezing, watery eyes and running nose.
Treatment with anti-histamines would block histamine receptors and relieve symptoms; the diagnosis can be confirmed by exposing her to small doses of various allergens (patch testing) to identify the specific one causing her reaction.

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Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 8

Applied Concept

During a polio eradication campaign, health workers administer oral polio vaccine to all children below 5 years. With reference to the chapter, explain the immunological principle behind this campaign and why it eradicates the disease.

The oral polio vaccine contains weakened (attenuated) poliovirus; when introduced into the body, it stimulates the immune system to mount a primary immune response and produce antibodies, while also generating immunological memory cells (B and T memory cells).
On subsequent natural exposure to wild poliovirus, the memory cells rapidly recognise the pathogen and mount a strong secondary (anamnestic) immune response, producing large amounts of antibodies that neutralise the virus before it causes disease.
When a sufficiently high proportion of a population is immunised (herd immunity), the virus cannot find susceptible hosts to infect; this breaks the chain of transmission and can lead to complete eradication, as demonstrated with smallpox.

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Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 9

Applied Concept

A 16-year-old student starts using drugs with friends at parties and gradually finds it impossible to stop even though he knows it is harming his academic and personal life. With reference to the chapter, explain the biological and psychological reasons for this inability to stop.

The student has developed addiction—a psychological attachment to the euphoria and temporary feeling of well-being associated with the drug; the brain's reward pathways are repeatedly activated, driving continued use even when self-destructive.
With repeated use, the tolerance of receptors in the body increases and they respond only to higher doses, leading to greater drug intake; this escalating cycle pulls the user into addiction from which escape without help is very difficult.
Physical dependence has also developed—if the student abruptly stops, withdrawal symptoms (anxiety, shakiness, nausea and sweating) manifest, making discontinuation physically painful; both psychological and physical dependence together create a powerful barrier to quitting without medical and counselling support.

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Application Question

Hard difficulty • Concept in a practical situation

Hard

Question 10

Applied Concept

A female athlete is found to have been taking anabolic steroids to improve performance. With reference to the chapter, describe the specific physical and physiological side effects she would likely suffer.

In females, anabolic steroid misuse causes masculinisation—the development of male-like features—including excessive hair growth on the face and body, enlargement of the clitoris and deepening of the voice.
Hormonal disruption results in abnormal menstrual cycles, increased aggressiveness, mood swings and depression; these effects may become permanent with prolonged use.
If the athlete is in adolescence, additional effects include severe facial and body acne and, critically, premature closure of the growth centres (epiphyseal plates) of long bones, leading to stunted growth—an irreversible consequence.

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Chapter sections

Chapter 7: Human Health and Disease | Application Questions

A 10-year-old child returns from school with dry, scaly, intensely itchy patches on the scalp. The family doctor suspects a fungal infection. With reference to the chapter, identify the disease, name the causative fungi and suggest two preventive measures.

A patient returning from a tropical area develops recurring high fever with chills every three to four days. Blood smear examination reveals ring-shaped forms inside RBCs. With reference to the chapter, identify the disease, causative organism and explain why the fever is periodic.

In a school canteen, several students develop stomach pain, constipation and blood-streaked stools after consuming food. The school doctor suspects amoebiasis. Explain how the infection spread and suggest measures to prevent future outbreaks.

A newborn baby is at risk of certain infections because its own immune system is not yet mature. With reference to the chapter, explain how the mother's body provides passive protection to the baby, giving two specific mechanisms.

A patient is brought to a hospital after a venomous snakebite. The doctor immediately administers an injection rather than waiting for the patient's immune system to respond. With reference to the chapter, explain what this injection contains and the principle behind this treatment.

A 30-year-old man who underwent a kidney transplant is prescribed immuno-suppressant drugs for life. With reference to the chapter, explain why these drugs are necessary and what would happen if they were stopped.

A woman who moves to a new city starts sneezing uncontrollably and her eyes become watery whenever she walks through a particular park. When she leaves the park, symptoms disappear. With reference to the chapter, explain the biological mechanism causing these symptoms.

During a polio eradication campaign, health workers administer oral polio vaccine to all children below 5 years. With reference to the chapter, explain the immunological principle behind this campaign and why it eradicates the disease.

A 16-year-old student starts using drugs with friends at parties and gradually finds it impossible to stop even though he knows it is harming his academic and personal life. With reference to the chapter, explain the biological and psychological reasons for this inability to stop.

A female athlete is found to have been taking anabolic steroids to improve performance. With reference to the chapter, describe the specific physical and physiological side effects she would likely suffer.

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