15 extra multiple-choice questions for Human Health and Diseases (12th Standard Zoology, Samacheer Kalvi), beyond the ones printed in the textbook — each with the correct option highlighted and a clear, worked explanation. Free to read in English and Tamil.
Q1
Which diagnostic test is commonly used to confirm a clinical diagnosis of typhoid fever?
- A. ELISA
- B. Western blot
- C. Widal testCorrect
- D. PCR
Explanation. Typhoid fever is a bacterial disease caused by Salmonella typhi, and its clinical diagnosis is confirmed using the Widal test.
Q2
In which specific part of the human body does the protozoan parasite Entamoeba histolytica primarily reside and feed on mucus and bacteria?
- A. Small intestine
- B. Stomach
- C. Large intestineCorrect
- D. Liver
Explanation. Entamoeba histolytica is the causative agent of amoebiasis, and it primarily lives in the human large intestine (colon), feeding on mucus and bacteria.
Q3
Tetanus, commonly known as lock jaw, is a bacterial disease characterized by painful muscle spasms. Which of the following is the causative pathogen of tetanus?
- A. Streptococcus pneumoniae
- B. Clostridium tetaniCorrect
- C. Salmonella typhi
- D. Mycobacterium tuberculosis
Explanation. Tetanus is caused by the bacterium Clostridium tetani, which enters the body through wound infections and affects muscle function, causing rigidity of jaw and face muscles.
Q4
Why is it exceptionally difficult to develop a universal vaccine against the common cold?
- A. The pathogen is a large multicellular helminth.
- B. It is caused by over 150 different strains of Rhino viruses whose RNA genome constantly mutates.Correct
- C. The virus remains dormant in the bone marrow for decades.
- D. It is caused by anaerobic spore-forming bacteria that resist antibodies.
Explanation. The common cold is caused by more than 150 strains of Rhino viruses, and their RNA genome undergoes frequent mutations, preventing a single effective vaccine.
Q5
During the erythrocytic stage of the Plasmodium life cycle in humans, yellowish-brown pigmented granules appear in the large schizont. What are these granules called?
- A. Haemozoin granules
- B. Nissl's granules
- C. Schuffner's granulesCorrect
- D. Acidophilic granules
Explanation. During the development of the trophozoite inside red blood cells, the large schizont shows yellowish-brown pigmented granules called Schuffner's granules.
Q6
Which mosquito species acts as the primary vector for transmitting both Dengue fever and Chikungunya to humans?
- A. Anopheles stephensi
- B. Culex pipiens
- C. Aedes aegyptiCorrect
- D. Mansonia uniformis
Explanation. Both Dengue fever and Chikungunya are viral infections transmitted to humans through the bite of infected female Aedes aegypti mosquitoes.
Q7
What is the infective stage of the protozoan parasite Entamoeba histolytica that penetrates the intestinal wall of the host?
- A. Cystic stage
- B. Sporozoite
- C. TrophozoiteCorrect
- D. Merozoite
Explanation. The trophozoite is the infective stage of Entamoeba histolytica, which penetrates the walls of the host's large intestine and secretes histolytic enzymes.
Q8
Ascaris lumbricoides, commonly known as the roundworm, is a parasite of the human intestine. How is this parasite classified based on its host requirements?
- A. Digenic parasite
- B. Monogenic parasiteCorrect
- C. Polygenic parasite
- D. Ectoparasite
Explanation. Ascaris lumbricoides is a monogenic parasite, meaning it completes its entire life cycle in a single host (humans) and exhibits sexual dimorphism.
Q9
Cannabinoids are a group of chemicals obtained from the hemp plant Cannabis sativa. Which neurotransmitter system do cannabinoids directly interfere with in the central nervous system?
- A. Acetylcholine
- B. Serotonin
- C. DopamineCorrect
- D. Gamma-aminobutyric acid (GABA)
Explanation. Cannabinoids interfere with the transport of the neurotransmitter dopamine and exert a potent stimulating action on the central nervous system.
Q10
Morphine is a widely abused narcotic drug extracted from the opium plant. What is its legitimate medical application?
- A. Central nervous system stimulant
- B. Pain killer used during surgeryCorrect
- C. Vaccine adjuvant for viral diseases
- D. Antidote for heavy metal poisoning
Explanation. Morphine is a clinically valuable pain killer used during surgery, but it is also a highly addictive depressant that slows down body functions.
Q11
A sedentary lifestyle can cause a deficiency of which vitamin, leading to fatigue, tiredness, bone loss, and muscle pain?
- A. Vitamin A
- B. Vitamin C
- C. Vitamin DCorrect
- D. Vitamin K
Explanation. A sedentary lifestyle often leads to a deficiency of Vitamin D, which in turn causes fatigue, bone loss, back pain, and muscle pain.
Q12
Irritable Bowel Syndrome (IBS) is a common gastrointestinal disorder characterized by stomach discomfort and abnormal bowel movements. What is identified as its primary cause?
- A. Bacterial infection by Vibrio cholerae
- B. High-caloric junk food intake
- C. Stress and associated illnessCorrect
- D. Heavy consumption of alcohol
Explanation. According to the text, stress and other illnesses are the main causes of irritable bowel syndrome.
Q13
Swine flu, which was first recognized in the 1919 pandemic and still circulates as a seasonal flu virus, is caused by which viral strain?
- A. H5N1
- B. H1N1Correct
- C. DENV-1
- D. Nipah virus
Explanation. Swine flu is caused by the H1N1 virus strain and presents symptoms such as fever, cough, sore throat, and body aches.
Q14
Which of the following statements is correct regarding the Nipah virus?
- A. It is a protozoan disease transmitted by houseflies.
- B. It is a zoonotic virus that can cause acute respiratory illness and fatal encephalitis.Correct
- C. It primarily infects the human large intestine, causing severe dysentery.
- D. It is easily treated and cured with broad-spectrum antibiotics.
Explanation. Nipah virus is a zoonotic virus transmitted from animals to humans, causing asymptomatic infection, respiratory illness, or fatal encephalitis.
Q15
Pneumonia is an infectious disease of the lungs caused by Streptococcus pneumoniae. Which of the following is a classic symptom of pneumonia?
- A. Thick mucopurulant nasal discharge
- B. Rigidity of jaw muscles and rapid heart rate
- C. Fever, cough, painful breathing, and brown sputumCorrect
- D. Reddish rashes on the skin, neck, and ears
Explanation. Pneumonia affects the lungs, leading to symptoms like fever, cough, painful breathing, and the production of brown sputum.
