The disease caused by protozoa is
Answer: D
Correct answer: malaria
Malaria is caused by Plasmodium, a protozoan, transmitted by the female Anopheles mosquito. Tuberculosis and typhoid are bacterial and polio viral.
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Which cannot fix atmospheric nitrogen in the soil?
Answer: D
Correct answer: Penicillium
Penicillium is a mould, and it fixes no nitrogen - it is famous for producing penicillin. Rhizobium fixes nitrogen symbiotically in root nodules, while Azotobacter and Clostridium do so free-living in the soil.
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The disease caused by fungi is
Answer: D
Correct answer: ringworm
Ringworm is a fungal infection of the skin - despite the name, no worm is involved; the ring is the advancing edge of the fungus. Measles, chicken pox and polio are all viral.
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Which bacterium helps in the setting of curd?
Answer: B
Correct answer: Lactobacillus
Lactobacillus ferments the lactose in milk to lactic acid. The acid lowers the pH until the milk protein casein coagulates, which is what sets the curd - and the acid also preserves it, by excluding other organisms.
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Which microorganism causes AIDS?
Answer: C
Correct answer: A virus
AIDS is caused by HIV, the human immunodeficiency virus - a retrovirus that infects CD4 helper T cells. Their gradual loss is what leaves the patient open to the opportunistic infections that define the disease.
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Which of the following diseases is spread by bacteria?
Answer: A
Correct answer: Tuberculosis
Tuberculosis is caused by Mycobacterium tuberculosis, a bacterium, which is why it can be treated with antibiotics - though a long course of several drugs is needed. Measles, chicken pox and polio are viral.
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Which of the following is not used as a food preservative?
Answer: D
Correct answer: Methane
Methane is a gas and preserves nothing. Salt and sugar preserve by drawing water out of microbial cells osmotically, and vinegar by acidity - all three work by making the food a place where microorganisms cannot grow.
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The process by which the amount of nitrogen in the atmosphere stays constant is known as the
Answer: C
Correct answer: nitrogen cycle
The nitrogen cycle keeps atmospheric nitrogen roughly constant: fixation by bacteria and lightning removes N2 from the air, and denitrification returns it. The two processes balance, so the atmosphere stays at about 78% nitrogen.
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Watering crops is called
Answer: B
Correct answer: irrigation
Supplying water to crops is irrigation. Sowing is putting the seed in the ground, tilling is loosening the soil beforehand, and manuring is adding nutrients.
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Spirogyra is
Answer: C
Correct answer: An algae
Spirogyra is a green alga - a filamentous freshwater form named for the spiral chloroplasts that run through each cell. It photosynthesises, which no protozoan, fungus or bacterium of this kind does.
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