Question Bank — Human Health and Disease

NCERT Class 12 Biology · Chapter 7 · CBSE Board Pattern

Class 12 Biology Chapter 7 Question Bank CBSE Board Pattern

Section A — MCQs (10 questions, 1 mark each)

  1. Which of the following is the causative agent of typhoid fever?
    (a) Streptococcus pneumoniae
    (b) Salmonella typhi
    (c) Plasmodium falciparum
    (d) Entamoeba histolytica

  2. The toxic substance released during rupture of RBCs in malaria that causes chill and high fever is:
    (a) Haemoglobin
    (b) Haemozoin
    (c) Interferon
    (d) Histamine

  3. Which cells of the innate immune system phagocytose and destroy microbes?
    (a) B-lymphocytes only
    (b) PMNL-neutrophils, monocytes and macrophages
    (c) Mast cells only
    (d) Plasma cells

  4. Assertion (A): AIDS is caused by a retrovirus that has an RNA genome enclosed by an envelope.
    Reason (R): HIV enters macrophages and helper T-lymphocytes where its RNA replicates to form viral DNA with the help of reverse transcriptase.
    (a) Both A and R are true and R is the correct explanation of A.
    (b) Both A and R are true but R is not the correct explanation of A.
    (c) A is true but R is false.
    (d) A is false but R is true.

  5. Malignant malaria, which can be fatal, is caused by:
    (a) Plasmodium vivax
    (b) Plasmodium malariae
    (c) Plasmodium falciparum
    (d) Entamoeba histolytica

  6. The exaggerated immune response to certain environmental antigens (allergens) is called:
    (a) Autoimmunity
    (b) Allergy
    (c) Acquired immunity
    (d) Innate immunity

  7. Assertion (A): Malignant tumours show the property of metastasis.
    Reason (R): Cancer cells have lost the property of contact inhibition and continue to divide uncontrollably.
    (a) Both A and R are true and R is the correct explanation of A.
    (b) Both A and R are true but R is not the correct explanation of A.
    (c) A is true but R is false.
    (d) A is false but R is true.

  8. The yellowish fluid secreted by the mother during the initial days of lactation that provides passive immunity to the newborn is:
    (a) Colostrum (rich in IgA)
    (b) Plasma
    (c) Lymph
    (d) Serum

  9. Which of the following is a helminthic disease?
    (a) Ringworm
    (b) Ascariasis
    (c) Amoebiasis
    (d) Pneumonia

  10. The most common infectious human ailment caused by rhinoviruses that affects the nose and respiratory passage but not the lungs is:
    (a) Pneumonia
    (b) Common cold
    (c) Typhoid
    (d) Filariasis

Section B — Very Short Answer (6 questions, 2 marks each)

  1. Differentiate between infectious and non-infectious diseases with one example of each.

  2. List any four barriers of innate immunity.

  3. Name the two types of lymphocytes involved in acquired immunity and state one function of each.

  4. What is the role of colostrum in providing immunity to a newborn?

  5. State two ways by which HIV is transmitted from an infected mother to her child.

  6. Differentiate between benign and malignant tumours.

Section C — Short Answer (5 questions, 3 marks each)

  1. Describe the life cycle of Plasmodium in the human host.

  2. Explain the structure of an antibody molecule. Why is the immune response also called humoral immune response?

  3. What are carcinogens? Give two examples and explain how they cause cancer.

  4. Describe any three measures for prevention and control of vector-borne diseases such as malaria and filariasis.

  5. Explain the mechanism by which AIDS virus causes deficiency of the immune system.

Section D — Long Answer (3 questions, 5 marks each)

  1. Describe the various public health measures that can be taken as safeguards against infectious diseases. (5 marks)

  2. Draw a well-labelled diagram of the structure of an antibody molecule. Explain the role of B-lymphocytes and T-lymphocytes in acquired immunity. (Diagram — 3 marks; explanation — 2 marks)

  3. What is drug abuse? Describe the effects of opioids, cannabinoids and coca alkaloids on the human body. Add a note on the role of family and teachers in prevention of drug/alcohol abuse among adolescents. (5 marks)

Section E — Case/Source-Based (2 questions, 4 marks each)

Case 1

Mary Mallon, nicknamed Typhoid Mary, was a cook who was a typhoid carrier. She continued to spread typhoid for several years through the food she prepared even though she herself showed no symptoms. Salmonella typhi enters the small intestine through contaminated food and water, migrates via blood and causes sustained high fever (39°–40°C), weakness, stomach pain and loss of appetite. The disease can be confirmed by Widal test.

(i) Name the bacterium that causes typhoid fever. (1 mark)
(ii) How does the pathogen enter the human body? (1 mark)
(iii) Mention two common symptoms of typhoid. (1 mark)
(iv) Why is personal and public hygiene important in preventing such water-borne diseases? (1 mark)

Case 2

A 25-year-old person with multiple sexual partners and a history of sharing needles for intravenous drug use reports to a hospital with symptoms of fever, diarrhoea and weight loss persisting for several months. ELISA test confirms HIV infection. The virus enters macrophages and helper T-lymphocytes, replicates and progressively reduces the number of T-helper cells, making the person susceptible to opportunistic infections.

(i) Expand the abbreviation AIDS. (1 mark)
(ii) Name the type of virus that causes AIDS and mention the enzyme it uses to replicate. (1 mark)
(iii) List any two high-risk groups for HIV infection mentioned in the chapter. (1 mark)
(iv) Why is prevention considered the best option for AIDS? Give one preventive measure. (1 mark)

▶ Answer Key Attempt all questions first,
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Section A

  1. (b)
  2. (b)
  3. (b)
  4. (a)
  5. (c)
  6. (b)
  7. (b)
  8. (a)
  9. (b)
  10. (b)

Section B

  1. Infectious: transmitted from person to person (e.g., typhoid); Non-infectious: not transmitted (e.g., cancer) — 1 + 1 mark.
  2. Physical (skin, mucus), Physiological (acid, saliva, tears), Cellular (WBCs, macrophages), Cytokine (interferons) — any four, ½ mark each.
  3. B-lymphocytes — produce antibodies; T-lymphocytes — help B cells / mediate CMI — 1 + 1 mark.
  4. Contains abundant IgA antibodies that protect the infant — 2 marks.
  5. Through placenta / during childbirth — 1 + 1 mark.
  6. Benign: remain confined, cause little damage; Malignant: invade tissues, show metastasis — 1 + 1 mark.

Section C

  1. Sporozoites enter via mosquito bite → multiply in liver cells → attack RBCs → rupture releasing haemozoin (fever) — 3 marks (sequential stages).
  2. H₂L₂ structure (two heavy, two light chains); B-lymphocytes secrete antibodies into blood (humoral response) — diagram points + explanation.
  3. Physical/chemical/biological agents causing cancer (X-rays, UV, tobacco smoke, oncogenic viruses) — 1 + 2 marks.
  4. Avoid water stagnation, use mosquito nets, introduce Gambusia, spray insecticides, wire mesh on doors/windows — any three, 1 mark each.
  5. HIV enters macrophages & T-helper cells → replicates using reverse transcriptase → reduces T-helper count → loss of immunity against opportunistic infections — 3 marks.

Section D

  1. Personal hygiene, public hygiene, safe drinking water, proper waste disposal, vaccination, vector control — 5 marking points.
  2. Labelled diagram of antibody (H₂L₂, variable & constant regions) — 3 marks; roles of B & T cells — 2 marks.
  3. Definition of drug abuse, effects of three groups (heroin depressant; marijuana affects CVS; cocaine euphoria/hallucination), role of parents/teachers in counselling and education — 5 marks.

Section E

Case 1

(i) Salmonella typhi — 1 mark
(ii) Through contaminated food and water — 1 mark
(iii) Sustained high fever, weakness/stomach pain (any two) — 1 mark
(iv) Prevents transmission via food/water — 1 mark

Case 2

(i) Acquired Immuno Deficiency Syndrome — 1 mark
(ii) HIV (retrovirus); reverse transcriptase — 1 mark
(iii) Persons with multiple sexual partners, intravenous drug users (any two) — 1 mark
(iv) No cure; use disposable needles/condoms/safe blood — 1 mark

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All questions are answerable from the NCERT chapter text. Reviewed by GFIS faculty.