Microbes in Human Welfare — Questions & Answers

Sample questions from Microbes in Human Welfare

1. Q1. Among the biofertilizers listed in NCERT, which group is autotrophic and can therefore fix nitrogen without depending on organic carbon from the soil or a host plant?

   • A.Rhizobium
   • B.Azotobacter
   • C.Cyanobacteria such as Anabaena and Nostoc✓
   • D.Glomus
   Solution

   Cyanobacteria are photosynthetic prokaryotes; they make their own organic carbon and many also fix nitrogen, so they enrich water-logged paddy fields where they grow freely in light. Rhizobium and Azotobacter are heterotrophs and Glomus is a fungus.

2. Q2. Compared to relying solely on chemical fertilizers, using an integrated approach combining biofertilizers with a reduced quantity of chemical fertilizers can potentially:

   • A.Maintain reasonable crop yield while reducing the total chemical input and associated environmental costs✓
   • B.Guarantee zero crop yield
   • C.Have no impact on chemical fertilizer requirements
   • D.Only be used in laboratory settings, never in actual farms
   Solution

   An integrated nutrient management approach combining biofertilizers with reduced chemical fertilizer doses is often promoted as a practical strategy to maintain productive crop yields while lowering total synthetic chemical input and its associated environmental costs.

3. Q3. Which of the following is the most accurate reason why chemical pesticide resistance has become a growing agricultural concern, making biocontrol alternatives increasingly attractive?

   • A.Repeated, widespread use of the same chemical pesticides can select for resistant pest populations over time, reducing the pesticide's long-term effectiveness✓
   • B.Chemical pesticides never lose effectiveness under any circumstances
   • C.Pest resistance is entirely unrelated to pesticide usage patterns
   • D.Biocontrol agents are always less effective than chemical pesticides regardless of resistance issues
   Solution

   Like antibiotic resistance in bacteria, repeated and widespread application of the same chemical pesticide can select for resistant pest populations over generations, prompting interest in biocontrol alternatives that may present different, complementary modes of action.

4. Q4. Baculoviruses are described as narrow-spectrum insecticidal applications. Which consequence of this narrow spectrum is correctly stated?

   • A.They are desirable because a single preparation controls all insect pests at once
   • B.They are undesirable because they kill every arthropod in the field
   • C.They are undesirable because they persist in mammals and cause disease
   • D.They are desirable in integrated pest management because they do not harm non-target insects, plants, mammals or birds, so beneficial insects are conserved✓
   Solution

   Most baculoviruses used in pest control are species-specific with narrow host ranges, so they have no negative impact on plants, mammals, birds, fish or non-target insects. That makes them especially valuable where conserving beneficial insects is important.

5. Q5. A sewage plant recycles part of its activated sludge into the aeration tank and sends the remainder elsewhere. Which pair of destinations and purposes is correct?

   • A.Recycled part is discharged into the river; remainder is stored as primary sludge
   • B.Recycled part is a chemical coagulant; remainder is spread on primary filtration screens
   • C.Recycled part is dried for biogas; remainder is aerated a second time
   • D.Recycled part acts as inoculum for aeration; remainder is pumped into anaerobic sludge digesters✓
   Solution

   A fraction of the settled flocs is pumped back to the aeration tank to serve as the inoculum of active aerobic microbes. The rest of the activated sludge is passed into large anaerobic sludge digesters, where other bacteria digest it and generate biogas.

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