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Science practice

Biology - Human Diseases & Immunity Questions with Answers

Human diseases and immunity questions cover communicable and non-communicable diseases, the causative organisms and vectors of common diseases, vaccination, the immune system and AIDS, as in NCERT class 9 Health and Disease. RRB Group D, ALP, NTPC and SSC papers regularly ask which organism causes a disease, which mosquito spreads it, or which vaccine prevents it. Tip: build a one-line table of disease, cause type and vector, and revise it often.

Formulas and key facts

  • Bacterial diseases: cholera, typhoid, tuberculosis, tetanus, diphtheria, anthrax
  • Viral diseases: common cold, influenza, polio, measles, chickenpox, dengue, rabies, AIDS
  • Protozoan diseases: malaria (Plasmodium), kala-azar, sleeping sickness, amoebic dysentery
  • Fungal disease: ringworm; worm diseases: elephantiasis (filariasis) and ascariasis
  • Malaria is spread by the female Anopheles mosquito; dengue by the Aedes mosquito; filariasis by the Culex mosquito
  • Antibiotics (such as penicillin) act on bacteria and do not work against viruses
  • Vaccination provides active immunity by exposing the body to a weakened or dead germ; BCG is for tuberculosis
  • DPT vaccine protects against diphtheria, whooping cough (pertussis) and tetanus
  • Smallpox was eradicated worldwide through vaccination
  • AIDS is caused by HIV, which damages the immune system by attacking white blood cells (helper T cells)
  • HIV spreads through infected blood, unsafe sexual contact, shared needles and from mother to child; not through touch or sharing food
  • Non-communicable diseases (such as diabetes and cancer) do not spread from person to person

Worked examples

Q1. Which organism causes malaria and which insect spreads it?

  1. Malaria is caused by a protozoan of the genus Plasmodium.
  2. It is carried and spread by the female Anopheles mosquito, which acts as the vector.

Answer: Plasmodium (a protozoan), spread by the female Anopheles mosquito

Q2. Why is penicillin not used to treat influenza?

  1. Influenza is caused by a virus.
  2. Antibiotics work by blocking biochemical pathways that bacteria use to make cell walls and other materials.
  3. Viruses do not have these pathways, so antibiotics cannot stop them.

Answer: Influenza is a viral disease and antibiotics act only on bacteria

Q3. Which of the following pairs is correctly matched? (A) Cholera: bacteria. (B) Dengue: bacteria. (C) Filariasis: worm. (D) Ringworm: protozoa.

  1. Cholera is caused by a bacterium, so (A) is correct.
  2. Dengue is caused by a virus, so (B) is incorrect.
  3. Filariasis is caused by a parasitic worm, so (C) is correct.
  4. Ringworm is caused by a fungus, so (D) is incorrect.

Answer: (A) and (C) are correct

Shortcuts that save time

  • Group diseases by cause type before an exam: bacteria, virus, protozoa, fungus, worm. Most questions ask only for the group, and knowing it removes half the options.
  • Learn mosquito vectors as three pairs: Anopheles with malaria, Aedes with dengue, Culex with filariasis. A confident pair beats a guess, which risks negative marking.
  • For immunity questions, remember that a vaccine prepares the body in advance (prevention), while an antibiotic treats an existing bacterial infection. Do not select antibiotics as the answer for any viral disease.

Where this appears

RRB Group DGeneral Science section
RRB ALPGeneral Science section
RRB NTPCGeneral Awareness section
SSC CGLGeneral Awareness section

Biology - Human Diseases & Immunity

Practice Set
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Refer to the two statements given below and choose the CORRECT option. Statement A: While writing the chemical formula of a compound, the total positive and negative charges must balance each other. Statement B: Balancing valencies ensures that the compound formed is electrically neutral.

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Biology - Human Diseases & Immunity questions with answers

10 sample questions from this topic with the correct option and the solution.

  1. Q1. Systolic pressure is measured when the heart __________.

    1. Stops beating
    2. Fills with blood
    3. Relaxes
    4. Contracts

    Answer: (D) Contracts

    Solution
    Systolic pressure is the pressure exerted on the artery walls when the heart contracts and pumps blood out into the arteries. It is the higher number in a blood pressure reading, while diastolic pressure is measured when the heart relaxes and fills with blood.

  2. Q2. Refer to the two statements given below and choose the CORRECT option. Statement A: Mixed cropping helps reduce the risk of total crop failure under adverse environmental conditions. Statement B: In mixed cropping, different crops are grown in a definite row arrangement to minimise competition.

    1. Both statements A and B are incorrect.
    2. Statement A is incorrect but B is correct.
    3. Both statements A and B are correct.
    4. Statement A is correct but B is incorrect.

    Answer: (D) Statement A is correct but B is incorrect.

    Solution
    Mixed cropping means growing two or more crops together on the same land without a definite row pattern. It reduces the risk of total crop failure because if one crop fails due to adverse conditions, the other may survive. So Statement A is correct. Statement B is incorrect because a definite row arrangement describes intercropping, not mixed cropping.

  3. Q3. The inner walls of the small intestine have thousands of finger-like outgrowths. These are called:

    1. myomas
    2. villi
    3. bronchi
    4. lumps

    Answer: (B) villi

    Solution
    The inner wall of the small intestine has numerous finger-like projections called villi. They greatly increase the surface area for absorption of digested food into the blood. Myomas are tumours, bronchi are air passages in the lungs, and lumps are not structures of the intestine.

  4. Q4. Select the correct option regarding the following two statements labelled Assertion (A) and Reason (R). Assertion (A): Monoculture plantations often fail to meet the diverse needs of forest-dependent villagers. Reason (R): These plantations provide medicinal herbs, food and fuel for villagers.

    1. Both A and R are true, and R is the correct explanation of A.
    2. Both A and R are true, but R is not the correct explanation of
    3. A is true, but R is false.
    4. A is false, but R is true.

    Answer: (C) A is true, but R is false.

  5. Q5. Name the world famous scientist known for his theory of relativity.

    1. Christian Bernard
    2. Thomas Alva Edison
    3. John Dalton
    4. Albert Einstein

    Answer: (D) Albert Einstein

    Solution
    Albert Einstein developed the theory of relativity (special relativity in 1905 and general relativity in 1915). He is one of the most famous physicists in the world and won the 1921 Nobel Prize in Physics for his work on the photoelectric effect.

  6. Q6. Medicines that stop the growth of disease causing microorganisms are called:

    1. antibodies
    2. antibiotics
    3. anaesthetics
    4. analgesic

    Answer: (B) antibiotics

    Solution
    Antibiotics are medicines that kill or stop the growth of disease-causing microorganisms such as bacteria. Antibodies are made by the body's own immune system, anaesthetics cause loss of sensation, and analgesics relieve pain. Hence the correct answer is antibiotics.

  7. Q7. Who suggested the four main groups of human blood in 1890?

    1. Karl Landsteiner
    2. Chadwick
    3. Louis Pasteur
    4. Ronald Ross

    Answer: (A) Karl Landsteiner

    Solution
    Karl Landsteiner discovered the ABO blood group system and classified human blood into the main groups A, B, AB and O around 1900-1901, for which he later won the Nobel Prize. Chadwick discovered the neutron, Louis Pasteur worked on germ theory and vaccines, and Ronald Ross discovered how malaria is transmitted. So Karl Landsteiner is the correct answer.

  8. Q8. Refer to the two statements given below and choose the CORRECT option. Statement A: Selective reabsorption in nephrons helps maintain water and salt balance in the body. Statement B: Selective reabsorption prevents nitrogenous wastes from entering the filtrate.

    1. Statement A is incorrect but B is correct.
    2. Both statements A and B are correct.
    3. Both statements A and B are incorrect.
    4. Statement A is correct but B is incorrect.

    Answer: (D) Statement A is correct but B is incorrect.

    Solution
    Selective reabsorption in the nephron returns useful substances such as glucose, amino acids, salts and water from the filtrate to the blood, which helps maintain the body's water and salt balance, so Statement A is correct. Nitrogenous wastes like urea are not reabsorbed and remain in the filtrate to be excreted; they do not need to be kept out of the filtrate since they are filtered into it. Hence Statement B is incorrect.

  9. Q9. Which of the following is NOT a seed-borne disease?

    1. Red rot of sugarcane
    2. Sheath rot on rice
    3. Potato mosaic
    4. Moulting of wheat

    Answer: (D) Moulting of wheat

    Solution
    Red rot of sugarcane, sheath rot of rice and potato mosaic are diseases that can be carried by seeds or planting material (setts, seeds, tubers) from one crop to the next. Moulting is a term for shedding of skin or feathers in animals and is not a seed-borne plant disease of wheat. So 'Moulting of wheat' is the one that is not a seed-borne disease.

  10. Q10. The cause of Hepatitis A is a:

    1. mosquito bite
    2. bacteria
    3. Virus
    4. protozoa

    Answer: (C) Virus