Chapter 8: Microbes in Human Welfare Assertion-Reason Questions | biology Class 12 CBSE

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Chapter 8: Microbes in Human Welfare Assertion-Reason Questions | biology Class 12 CBSE | ByteNotes.in

Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 1

Logic Check

Assertion (A): Lactic acid bacteria (LAB) improve the nutritional quality of curd. Reason (R): LAB produce acids that coagulate milk proteins and also increase vitamin B12 content.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 2

Logic Check

Assertion (A): Dosa and idli batter rises when left overnight. Reason (R): Bacteria in the batter undergo aerobic respiration and produce CO2.

Reasoning Options

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Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 3

Logic Check

Assertion (A): Swiss cheese has characteristic large holes. Reason (R): The large holes in Swiss cheese are formed due to CO2 produced by Propionibacterium sharmanii.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 4

Logic Check

Assertion (A): Wine and beer can be produced without distillation. Reason (R): These beverages require higher ethanol concentration than whisky or brandy.

Reasoning Options

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Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 5

Logic Check

Assertion (A): Penicillin was the first antibiotic to be discovered. Reason (R): Alexander Fleming discovered it by chance when he observed inhibition of Staphylococci growth by Penicillium notatum.

Reasoning Options

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Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 6

Logic Check

Assertion (A): BOD of untreated sewage water is higher than that of treated effluent. Reason (R): Sewage treatment reduces organic matter, thereby lowering the BOD of water.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 7

Logic Check

Assertion (A): Activated sludge from settling tanks is completely discarded after secondary treatment. Reason (R): A small portion of activated sludge is recycled back as inoculum into the aeration tank.

Reasoning Options

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Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 8

Logic Check

Assertion (A): Methanogens are found in the rumen of cattle. Reason (R): Methanogens help break down cellulosic material in the cattle's rumen and play a role in cattle nutrition.

Reasoning Options

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Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 9

Logic Check

Assertion (A): Biogas plants are more commonly built in rural areas. Reason (R): Cattle dung, which is rich in methanogens and used for biogas production, is abundantly available in rural areas.

Reasoning Options

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Assertion-Reason

Hard difficulty • Check the statement and reason

Hard

Question 10

Logic Check

Assertion (A): Bacillus thuringiensis (Bt) toxin kills only the target caterpillars and leaves other insects unharmed. Reason (R): The Bt toxin is released only in the alkaline gut environment of insect larvae and is inactive in other environments.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 11

Logic Check

Assertion (A): Rhizobium is an example of a free-living nitrogen-fixing bacterium. Reason (R): Rhizobium forms nodules in the roots of leguminous plants and fixes atmospheric nitrogen.

Reasoning Options

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Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 12

Logic Check

Assertion (A): Mycorrhizal associations help plants absorb phosphorus from the soil. Reason (R): The fungal symbiont in mycorrhiza absorbs phosphorus from soil and passes it to the plant.

Reasoning Options

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Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 13

Logic Check

Assertion (A): Cyclosporin A is used to treat patients who have undergone organ transplantation. Reason (R): Cyclosporin A acts as an immunosuppressive agent to prevent organ rejection.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 14

Logic Check

Assertion (A): Statins are used to lower blood cholesterol levels. Reason (R): Statins act by competitively inhibiting the enzyme responsible for the synthesis of cholesterol.

Reasoning Options

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Assertion-Reason

Hard difficulty • Check the statement and reason

Hard

Question 15

Logic Check

Assertion (A): Baculoviruses are excellent biocontrol agents because they target a wide range of organisms. Reason (R): Baculoviruses are narrow-spectrum, species-specific agents with no negative impacts on non-target organisms.

Reasoning Options

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Assertion-Reason

Medium difficulty • Check the statement and reason

Medium

Question 16

Logic Check

Assertion (A): Aspergillus niger is used for the commercial production of citric acid. Reason (R): Aspergillus niger is a bacterium that naturally secretes large amounts of citric acid.

Reasoning Options

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Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 17

Logic Check

Assertion (A): Bottled fruit juices are clearer than freshly made home juices. Reason (R): Bottled juices are clarified by the use of pectinases and proteases.

Reasoning Options

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Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 18

Logic Check

Assertion (A): Lipases are used in detergent formulations. Reason (R): Lipases help remove oily and fatty stains from clothes during laundry.

Reasoning Options

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Assertion-Reason

Hard difficulty • Check the statement and reason

Hard

Question 19

Logic Check

Assertion (A): Chemical fertilisers have caused significant environmental pollution. Reason (R): Chemical fertilisers are non-degradable and accumulate in the soil permanently, making it toxic.

Reasoning Options

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Assertion-Reason

Easy difficulty • Check the statement and reason

Easy

Question 20

Logic Check

Assertion (A): Cyanobacteria serve as important biofertilisers in paddy fields. Reason (R): Cyanobacteria such as Anabaena, Nostoc, and Oscillatoria can fix atmospheric nitrogen and add organic matter to the soil.

Reasoning Options

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Chapter sections

Chapter 8: Microbes in Human Welfare | Assertion-Reason

Assertion (A): Lactic acid bacteria (LAB) improve the nutritional quality of curd. Reason (R): LAB produce acids that coagulate milk proteins and also increase vitamin B12 content.

Assertion (A): Dosa and idli batter rises when left overnight. Reason (R): Bacteria in the batter undergo aerobic respiration and produce CO2.

Assertion (A): Swiss cheese has characteristic large holes. Reason (R): The large holes in Swiss cheese are formed due to CO2 produced by Propionibacterium sharmanii.

Assertion (A): Wine and beer can be produced without distillation. Reason (R): These beverages require higher ethanol concentration than whisky or brandy.

Assertion (A): Penicillin was the first antibiotic to be discovered. Reason (R): Alexander Fleming discovered it by chance when he observed inhibition of Staphylococci growth by Penicillium notatum.

Assertion (A): BOD of untreated sewage water is higher than that of treated effluent. Reason (R): Sewage treatment reduces organic matter, thereby lowering the BOD of water.

Assertion (A): Activated sludge from settling tanks is completely discarded after secondary treatment. Reason (R): A small portion of activated sludge is recycled back as inoculum into the aeration tank.

Assertion (A): Methanogens are found in the rumen of cattle. Reason (R): Methanogens help break down cellulosic material in the cattle's rumen and play a role in cattle nutrition.

Assertion (A): Biogas plants are more commonly built in rural areas. Reason (R): Cattle dung, which is rich in methanogens and used for biogas production, is abundantly available in rural areas.

Assertion (A): Bacillus thuringiensis (Bt) toxin kills only the target caterpillars and leaves other insects unharmed. Reason (R): The Bt toxin is released only in the alkaline gut environment of insect larvae and is inactive in other environments.

Assertion (A): Rhizobium is an example of a free-living nitrogen-fixing bacterium. Reason (R): Rhizobium forms nodules in the roots of leguminous plants and fixes atmospheric nitrogen.

Assertion (A): Mycorrhizal associations help plants absorb phosphorus from the soil. Reason (R): The fungal symbiont in mycorrhiza absorbs phosphorus from soil and passes it to the plant.

Assertion (A): Cyclosporin A is used to treat patients who have undergone organ transplantation. Reason (R): Cyclosporin A acts as an immunosuppressive agent to prevent organ rejection.

Assertion (A): Statins are used to lower blood cholesterol levels. Reason (R): Statins act by competitively inhibiting the enzyme responsible for the synthesis of cholesterol.

Assertion (A): Baculoviruses are excellent biocontrol agents because they target a wide range of organisms. Reason (R): Baculoviruses are narrow-spectrum, species-specific agents with no negative impacts on non-target organisms.

Assertion (A): Aspergillus niger is used for the commercial production of citric acid. Reason (R): Aspergillus niger is a bacterium that naturally secretes large amounts of citric acid.

Assertion (A): Bottled fruit juices are clearer than freshly made home juices. Reason (R): Bottled juices are clarified by the use of pectinases and proteases.

Assertion (A): Lipases are used in detergent formulations. Reason (R): Lipases help remove oily and fatty stains from clothes during laundry.

Assertion (A): Chemical fertilisers have caused significant environmental pollution. Reason (R): Chemical fertilisers are non-degradable and accumulate in the soil permanently, making it toxic.

Assertion (A): Cyanobacteria serve as important biofertilisers in paddy fields. Reason (R): Cyanobacteria such as Anabaena, Nostoc, and Oscillatoria can fix atmospheric nitrogen and add organic matter to the soil.

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