Microbes in Human Welfare is a Class 12 Botany chapter in the NEET (UG) syllabus. NEET720 has 658 reviewed practice questions on it, each with a quick answer and a step-by-step explanation. The 8 questions below are free and fixed, so you can bookmark this page; the full chapter, plus mistake tracking and spaced revision, is in the app.
103
easy
437
medium
118
hard
Topics covered
Microbes in Household and Industrial Products · Sewage Treatment and Biogas · Biocontrol Agents and Biofertilisers · Industrial production · Microbes as biofertilisers and biocontrol agents · Microbes in industrial production · Microbes and antibiotics · Statins · Microbes in food industry · Microbes in Sewage Treatment · Microbes as Biocontrol Agents · Microbes as Biocontrol Agents · Microbes as Biofertilisers · Microbes in Industrial Products · Microbes as Biofertilisers · Human Welfare/Biotechnology · Fermented foods · Fermented beverages · Industrial products · Biogas production · Mycorrhizae · Biofertilizer advantages · Biopesticides · Beverages via fermentation · Antibiotics mechanism · Industrial enzymes · Fermenters/industrial scale production · Biogas plant structure · Vinegar production · Butter and butyric acid · Sewage treatment significance · Microbes as source of enzymes · Antibiotic resistance concern · Fermented food/beverage examples · Biofertilizer categories · Biopesticide advantage · Microbes and human health · Biogas composition · Single cell protein · Sewage treatment output
8 free Microbes in Human Welfare practice questions with answers
Choose an answer in your head before opening it. Each explanation says why the correct option is right and, where relevant, why the tempting wrong option is wrong.
Question 1 · easy · Biocontrol Agents and Biofertilisers
Biological control of pests and diseases refers to the use of
- A.biological methods and living organisms to control pests and diseases instead of relying on toxic chemicals
- B.synthetic pesticides derived from petroleum-based chemicals applied in reduced doses
- C.genetically modified pesticide molecules that mimic natural insect hormones
- D.irradiation of stored grains to sterilise insect pests before use
Show answer and explanation
Answer: A. biological methods and living organisms to control pests and diseases instead of relying on toxic chemicals
Biological control uses living organisms (bacteria, fungi, viruses, insects) rather than toxic chemicals to manage pests and pathogens, avoiding environmental damage.
NCERT defines biological control as the use of biological methods/living organisms for controlling plant diseases and pests, as an alternative to hazardous chemical pesticides and fungicides. Option B, C and D describe chemical or physical methods, not biological control.
Common mistake: Confusing 'reduced chemical dose' with 'biological' control.
Key point: Biological control = living organisms replacing toxic agrochemicals.
Question 2 · easy · Biocontrol Agents and Biofertilisers
Excessive use of chemical pesticides and fungicides in agriculture is discouraged mainly because it
- A.increases soil nitrogen content beyond the requirement of the crop
- B.pollutes the environment, harms beneficial organisms, disrupts food chains and leads to development of resistance in pests
- C.makes seeds dormant for a longer period, delaying germination
- D.reduces the water-holding capacity of soil particles permanently
Show answer and explanation
Answer: B. pollutes the environment, harms beneficial organisms, disrupts food chains and leads to development of resistance in pests
Overuse of chemical pesticides pollutes the environment, kills non-target beneficial organisms, disrupts food chains, and pests evolve resistance — this is the core NCERT rationale for promoting biocontrol.
NCERT explicitly lists environmental pollution, harm to beneficial organisms, disruption of food chains, and pest resistance development as consequences of excessive chemical pesticide/fungicide use. Options B, C, D describe unrelated or fabricated effects.
Common mistake: Mixing up pesticide harms with fertiliser-related soil issues.
Key point: Chemical pesticide overuse: pollution + kills beneficial species + disrupts food chains + resistance evolution.
Question 3 · easy · Biocontrol Agents and Biofertilisers
Bacillus thuringiensis, when grown in a culture, forms characteristic protein crystals that contain
- A.chlorophyll pigments that give the bacterial colony a green colour
- B.antibiotic molecules that inhibit growth of competing soil fungi
- C.a toxic insecticidal protein active against specific groups of insect larvae
- D.plant growth-promoting hormones similar to auxins
Show answer and explanation
Answer: C. a toxic insecticidal protein active against specific groups of insect larvae
Bacillus thuringiensis produces protein crystals containing a toxin that is insecticidal to specific insect larvae, forming the basis of Bt-based biopesticides and Bt transgenic crops.
The Bt crystal protein (cry protein) is toxic only when ingested by susceptible larvae. It is neither a pigment, antibiotic, nor a hormone. This distinction is central to understanding Bt's mechanism as a biopesticide.
Common mistake: Confusing Bt toxin with Penicillium's antibiotic role.
Key point: Bt crystal = insecticidal protein toxin, not pigment/antibiotic/hormone.
Question 4 · easy · Biocontrol Agents and Biofertilisers
Rhizobium enriches soil nitrogen content by forming a symbiotic association specifically with the roots of
- A.all cereal crops including wheat and rice
- B.aquatic ferns such as Azolla
- C.any plant growing in nitrogen-deficient soil
- D.leguminous plants
Show answer and explanation
Answer: D. leguminous plants
Rhizobium forms root nodules specifically on leguminous plants and fixes atmospheric nitrogen into a usable form for the plant.
This symbiosis is host-specific to legumes (family Fabaceae). Cereals like wheat/rice do not host Rhizobium nodules; Azolla instead harbours the cyanobacterium Anabaena azollae, not Rhizobium.
Common mistake: Mixing Rhizobium (legume symbiont) with Anabaena-Azolla (fern symbiont).
Key point: Rhizobium = symbiotic N-fixer of legume root nodules only.
Question 5 · medium · Biocontrol Agents and Biofertilisers
Baculoviruses used as biological control agents mostly belong to the genus
- A.Bacillus
- B.Nucleopolyhedrovirus
- C.Trichoderma
- D.Azotobacter
Show answer and explanation
Answer: B. Nucleopolyhedrovirus
Most baculoviruses used in biological pest control belong to the genus Nucleopolyhedrovirus (NPV), which are species-specific insecticidal pathogens.
NCERT specifically names Nucleopolyhedrovirus as the genus to which most biocontrol baculoviruses belong. Bacillus, Trichoderma and Azotobacter are unrelated organisms used for different biocontrol/biofertiliser purposes.
Common mistake: Mixing up the viral genus name with bacterial/fungal biocontrol agent names.
Key point: Baculovirus biocontrol agents mostly = genus Nucleopolyhedrovirus (NPV).
Question 6 · medium · Biocontrol Agents and Biofertilisers
Ladybird beetles and dragonflies are traditionally used as biocontrol agents against, respectively,
- A.lepidopteran caterpillars and aphids
- B.mosquitoes and aphids
- C.aphids and mosquitoes
- D.root-knot nematodes and whiteflies
Show answer and explanation
Answer: C. aphids and mosquitoes
Ladybird beetles are classic predators of aphids on crops, while dragonflies help control mosquito populations — both are traditional examples of predator-based biological control.
NCERT cites ladybird (to get rid of aphids) and dragonflies (to control mosquitoes) as familiar examples of biological control using organisms already present in nature, predating modern microbial biocontrol methods.
Common mistake: Reversing which predator controls which pest.
Key point: Ladybird -> aphids; Dragonfly -> mosquitoes.
Question 7 · medium · Biocontrol Agents and Biofertilisers
In the mycorrhizal association formed by fungi such as Glomus with plant roots, the fungal partner mainly
- A.fixes atmospheric nitrogen and converts it into nitrates for plant uptake
- B.produces insecticidal toxins that protect the root from insect larvae
- C.decomposes soil organic matter into humus without any plant benefit
- D.absorbs phosphorus from soil and passes it to the plant, receiving organic nutrients in return
Show answer and explanation
Answer: D. absorbs phosphorus from soil and passes it to the plant, receiving organic nutrients in return
Mycorrhiza is a mutualistic association where the fungus (e.g., Glomus) absorbs soil phosphorus and supplies it to the plant, while the plant provides organic nutrients to the fungus.
This phosphorus-for-organic-nutrient exchange also confers benefits like increased resistance to root-borne pathogens and tolerance to salinity and drought. Nitrogen fixation is the role of Rhizobium/Azospirillum/Azotobacter/cyanobacteria, not Glomus.
Common mistake: Assuming all root-associated microbes fix nitrogen.
Key point: Mycorrhiza (Glomus) = phosphorus absorption + stress tolerance, NOT nitrogen fixation.
Question 8 · medium · Biocontrol Agents and Biofertilisers
Cyanobacteria such as Anabaena and Nostoc are commonly used as biofertilisers in paddy fields mainly because they
- A.are heterotrophic bacteria that decompose stubble left after harvesting
- B.are autotrophic microbes that fix atmospheric nitrogen and thrive well under the flooded conditions of paddy fields
- C.produce Bt-like insecticidal crystal proteins that protect the paddy crop from pests
- D.form root nodules on the rice plant similar to Rhizobium nodules on legumes
Show answer and explanation
Answer: B. are autotrophic microbes that fix atmospheric nitrogen and thrive well under the flooded conditions of paddy fields
Anabaena and Nostoc are autotrophic, nitrogen-fixing cyanobacteria well suited to the flooded, aquatic conditions of paddy fields, making them effective natural biofertilisers there.
Unlike Rhizobium, cyanobacteria do not require root nodulation to fix nitrogen — they fix it independently while free-living in water/soil, which is why they are especially valuable in flooded paddy cultivation. They are photosynthetic (autotrophic), not decomposers, and do not produce Bt-like toxins.
Common mistake: Assuming cyanobacteria nodulate roots like Rhizobium.
Key point: Anabaena/Nostoc = autotrophic N-fixers ideal for flooded paddy fields, non-nodulating.
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Questions about Microbes in Human Welfare for NEET
How many NEET questions does NEET720 have on Microbes in Human Welfare?＋
NEET720 has 658 reviewed practice questions on Microbes in Human Welfare (Botany): 103 easy, 437 medium and 118 hard. 8 of them are free on this page with full explanations; the rest are available in the app.
Is Microbes in Human Welfare a Class 11 or Class 12 chapter for NEET?＋
Microbes in Human Welfare is a Class 12 Botany chapter in the NEET (UG) syllabus. Read the NCERT chapter first, then practise chapter-wise MCQs and previous-year questions.
How should I practise Microbes in Human Welfare for NEET?＋
Attempt the questions below without looking at the options for more than a few seconds, mark your answer, then read the explanation even when you were right. Record every mistake and revisit it after a gap. On NEET720 this happens automatically: wrong answers go to your Mistake Book and are scheduled for spaced revision.
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Questions are original NEET720 compositions reviewed for correctness, syllabus fit and option quality. Counts update as the bank grows (658 active practice questions in this chapter today).