Test: Microbes in Human Welfare - 1 - NEET MCQ

Microbes such as Lactobacillus and others commonly called lactic acid bacteria (LAB) grow in milk and convert it into curd.

Hence, the correct option is C.
NCERT Reference: Topic- " MICROBES IN HOUSEHOLD PRODUCTS” of chapter "Microbes in Human Welfare" of NCERT 

Line in NCERT: "Micro-organisms such as Lactobacillus and others commonly called lactic acid bacteria (LAB) grow in milk and convert it to curd."

Saccharomyces is a yeast that is used to ferment sugar to produce ethanol in absence of oxygen or by anaerobic respiration.

Hence, the correct option is B.
NCERT Reference: Topic Fermented Beverages” of chapter "Microbes in Human Welfare" of NCERT.  

Line in NCERT: "Yeast (Saccharomyces cerevisiae) is used for commercial production of ethanol."

• The puffed-up appearance of dough is due to the production of CO₂ gas.
• Baking soda (sodium hydrogen carbonate) on heating releases carbon dioxide gas along with sodium carbonate.

Hence, the correct option is B.
NCERT Reference: Topic- MICROBES IN HOUSEHOLD PRODUCTS of chapter "Microbes in Human Welfare" of NCERT.  

Line in NCERT: "The puffed-up appearance of dough is due to the production of CO2 gas."

• Clostridium butylicum is used to produce butyric acid.
• Butyric acid is an important industrial chemical used to process food items.

Hence, the correct option is A.
NCERT Reference: Topic-  Chemicals, Enzymes and other Bioactive Molecules” of chapter "Microbes in Human Welfare" of NCERT.  

Line in NCERT: "Examples of acid producers are Aspergillus niger (a fungus) of citric acid, Acetobacter aceti (a bacterium) of acetic acid; Clostridium butylicum (a bacterium) of butyric acid and Lactobacillus (a bacterium) of lactic acid."

• Mycorrhiza is a symbiotic association between fungus and angiosperms.
• The most common fungal partners of mycorrhiza are the Glomus species.

Hence, the correct option is D.
NCERT Reference: Topic- MICROBES AS BIOFERTILISERS” of chapter "Microbes in Human Welfare" of NCERT.  

Line in NCERT: "Many members of the genus Glomus form mycorrhiza."

• Yeast is used in the production of alcohol, wine-making and in baking bread.
• Saccharomyces cerevisiae is known as baker's yeast and Saccharomyces ellipsoidens is called wine yeast. 

Hence, the correct  option is D.
NCERT Reference: Topic- Fermented Beverages” of chapter "Microbes in Human Welfare" of NCERT.  

Line in NCERT: "Microbes especially yeasts have been used from time immemorial for the production of beverages like wine, beer, whisky, brandy or rum."

• The biogas-producing bacteria are collectively known as methanogens and one such common bacterium is Methanobacterium.
• These bacteria are commonly found in the anaerobic sludge during sewage treatment and also in the rumen of cattle.

Hence, the correct option is D.

Topic in NCERT: MICROBES IN PRODUCTION OF BIOGAS

Line in NCERT: "These bacteria are collectively called methanogens, and one such common bacterium is Methanobacterium."

• The type of gas produced depends upon the microbes and the organic substrates they utilise.
• Example: In the fermentation of dough, cheese making and production of beverages, the main gas produced is CO₂.

Hence, the correct option is C.
NCERT Reference: Topic- MICROBES IN PRODUCTION OF BIOGAS” of chapter "Microbes in Human Welfare" of NCERT.  

Line in NCERT: "The type of the gas produced depends upon the microbes and the organic substrates they utilise."

• The first organic acid produced by microbial fermentation was lactic acid.
• Lactic acid is produced by the anaerobic respiration of glucose.

Hence, the correct option is C.
NCERT Reference: Topic- Chemicals, Enzymes and other Bioactive Molecules” of chapter "Microbes in Human Welfare" of NCERT.  

Line in NCERT: "Lactobacillus (a bacterium) of lactic acid."

• Treatment of wastewater is done by the heterotrophic microbes naturally present in the sewage.
• This treatment is carried out in two stages:
  (i) Primary Treatment  
  (ii) Secondary Treatment

Hence, the correct option is B.
NCERT Reference: Topic- MICROBES IN SEWAGE TREATMENT” of chapter "Microbes in Human Welfare" of NCERT.  

Line in NCERT: "Treatment of waste water is done by the heterotrophic microbes naturally present in the sewage."

• Due to the development of various methods of genetic engineering, in the last decade or so, scientists have introduced Bacillus thuringiensis toxin genes into the plants. Such plants are resistant to attack by insect pests.
• These are available in sachets as dried spores which are mixed with water and sprayed onto vulnerable plants such as brassicas and fruit trees, where these are eaten by the insect larvae. In the gut of the larvae, the toxin is released and the larvae get killed. The bacterial disease will kill the caterpillars, but leave other insects unharmed.
• Bt-cotton is one such example, which is being cultivated in some states of our country.

Hence, the correct option is A.
NCERT Reference: Topic- MICROBES AS BIOCONTROL AGENTS” of chapter "Microbes in Human Welfare" of NCERT.  

Line in NCERT: "Bt-cotton is one such example, which is being cultivated in some states of our country."

• Methane is also called marsh gas because it is produced by the anaerobic bacterial decomposition of vegetable matter underwater or in a marshy area. 
• The decomposition of sludge by anaerobic bacteria in sewage-treatment processes also produces a gas rich in methane. This gas has a pungent smell and is highly flammable.

Hence, the correct option is D.
NCERT Reference: Topic- MICROBES IN SEWAGE TREATMENT” of chapter "Microbes in Human Welfare" of NCERT.  

Line in NCERT: "These bacteria are commonly found in the anaerobic sludge during sewage treatment."

Secondary treatment of sewage is also called biological treatment because in this treatment aeration of sewage water is done that increases the microbes that decompose the organic materials in sewage water.

Hence, the correct option is A.
NCERT Reference: Topic- MICROBES IN SEWAGE TREATMENT” of chapter "Microbes in Human Welfare" of NCERT.  

Line in NCERT: "Secondary treatment or Biological treatment: The primary effluent is passed into large aeration tanks where it is constantly agitated mechanically and air is pumped into it."

• Biological oxygen demand is the amount of oxygen required to completely decompose the organic waste present in one litre of water by bacteria.
• A high value of BOD shows that water is highly polluted.

Hence, the correct option is A.
NCERT Reference: Topic- MICROBES IN SEWAGE TREATMENT” of chapter "Microbes in Human Welfare" of NCERT.  

Line in NCERT: "The greater the BOD of waste water, more is its polluting potential."

• Some of the aerobic nitrogen-fixing bacteria are Azotobacter and Beijerinckia.
• Some of the anaerobic nitrogen-fixing bacteria are Clostridium, Rhodospirillum and Rhodopseudomonas.
• Soil is enriched through exudation and the formation of nitrates after their death and decay.

Hence, the correct option is A.
NCERT Reference: Topic- MICROBES AS BIOFERTILISERS” of chapter "Microbes in Human Welfare" of NCERT.  

• Atmospheric nitrogen is not available to plants. There are certain nitrogen-fixing bacteria that convert atmospheric nitrogen into ammonium compounds and make them available to the plants.Examples: Azotobacter, Frankia, Rhizobium, Azospirillum.
• Out of these, Azospirillum is widely used as a nitrogen fixer organism in paddy fields. It is used as a biofertilizer in rice fields. It promotes plant growth.

Hence, the correct option is D.
NCERT Reference: Topic- MICROBES AS BIOFERTILIZERS” of chapter "Microbes in Human Welfare" of NCERT.  

• Rhizobium is a nitrogen-fixing bacteria found in the nodule of a leguminous plant's root.
• These bacteria fix atmospheric nitrogen into organic forms, which is used by the plant as nutrient.
• It increases the fertility of the soil.

Hence, the correct option is D.
NCERT Reference: Topic: MICROBES AS BIOFERTILIZERS” of chapter "Microbes in Human Welfare" of NCERT.  

Line in NCERT: "You have studied about the nodules on the roots of leguminous plants formed by the symbiotic association of Rhizobium."

• Baculoviruses are pathogens that attack insects and other arthropods.
• The majority of baculoviruses used as biological control agents fall under the genus Nucleopolyhedrovirus.

Hence, the correct option is C.
NCERT Reference: Topic- MICROBES AS BIOCONTROL AGENTS” of chapter "Microbes in Human Welfare" of NCERT.  

Line in NCERT: "Baculoviruses are pathogens that attack insects and other arthropods."

Explanation of Assertion: Biofertilizers are living microorganisms that, when applied to seeds, plant surfaces, or soil, colonize the rhizosphere or the interior of the plant and promote growth by increasing the supply or availability of primary nutrients to the host plant. They are a natural and environmentally friendly way to provide essential nutrients to plants, which in turn boosts soil fertility and productivity.

Explanation of Reason: Organic farming is an agricultural system that seeks to provide the consumer with fresh, tasty, and authentic food while respecting natural life-cycle systems. It involves the use of natural fertilizers, such as compost, manure, and green manure, instead of synthetic fertilizers. It also relies on natural pest control methods, such as biological control, crop rotation, and the use of resistant plant varieties, instead of chemical pesticides.

While both the assertion and reason are correct statements, the reason does not directly explain the assertion. The assertion is about the role of biofertilizers in enriching soil nutrients, while the reason is about the principles of organic farming, which is a broader concept that encompasses not only the use of biofertilizers but also other natural and sustainable practices.

Line in NCERT: "Biofertilisers are organisms that enrich the nutrient quality of the soil."

BOD refers to the amount of the oxygen that would be consumed if all the organic matter in one liter of water were oxidised by bacteria.

Line in NCERT: "The BOD test measures the rate of uptake of oxygen by micro-organisms in a sample of water and thus, indirectly, BOD is a measure of the organic matter present in the water."

Bio-fertilizer enriches the nutrient in the soil. The main sources of bio-fertilizers are bacteria, fungi and cyanobacteria.

Hence, the correct option is D.
NCERT Reference: Topic- MICROBES AS BIOFERTILISERS” of chapter "Microbes in Human Welfare" of NCERT.  

Line in NCERT: "The main sources of biofertilisers are bacteria, fungi and cyanobacteria."

• This allows vigorous growth of useful aerobic microbes into flocs (masses of bacteria associated with fungal filaments to form mesh like structures).
• Once the BOD of sewage or waste water is reduced significantly, the effluent is then passed into a settling tank where the bacterial ‘flocs’ are allowed to sediment.
• This sediment is called activated sludge.

• Microbes are not used in the production of antiviral drugs and the production of inorganic fertilizers.
• Although, microbes are used in converting milk into curd, antibiotic production, sewage treatment, bread and cheese industry etc.

Hence, the correct option is C.
NCERT Reference: Topic- MICROBES IN SEWAGE TREATMENT” and  MICROBES IN INDUSTRIAL PRODUCTS” of chapter "Microbes in Human Welfare" of NCERT.  

A biological control being developed for use in the treatment of plant disease is the fungus Trichoderma. Trichoderma species are free-living fungi that are very common in the root ecosystems. They are effective biocontrol agents of several plant pathogens.

Line in NCERT: "A biological control being developed for use in the treatment of plant disease is the fungus Trichoderma. Trichoderma species are free-living fungi that are very common in the root ecosystems. They are effective biocontrol agents of several plant pathogens."

• Alexander Fleming while working on Staphylococci bacteria, once observed a mould growing in one of his unwashed culture plates around which Staphylococci could not grow.
• He found out that it was due to a chemical produced by the mould and he named it Penicillin after the mould Penicillium notatum.