Test: Microbes in Human Welfare- 1


25 Questions MCQ Test Biology Class 12 | Test: Microbes in Human Welfare- 1


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QUESTION: 1

Micro-organisms that grow in milk and convert it to curd are commonly called _________.

Solution:

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

QUESTION: 2

Ethanol is commercially produced through a particular species of _________.

Solution:

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

QUESTION: 3

The puffed-up appearance of dough is due to production of?      

Solution:
  • The puffed-up appearance of dough is due to the production of CO2 gas.
  • Baking soda (sodium hydrogen carbonate) on heating release carbon dioxide gas along with sodium carbonate.
QUESTION: 4

Which of the following bacterium produces butyric acid?

Solution:
  • Clostridium butylicum is used to produce butyric acid.
  • Butyric acid is important industrial chemicals used to process food items.
QUESTION: 5

The most common fungal partners of mycorrhiza are _________ species.

Solution:
  • Mycorrhiza is a symbiotic association between fungus and angiosperms.
  • The most common fungal partners of mycorrhiza are the Glomus species.
QUESTION: 6

Yeast is used in the production of:

Solution:

Yeast is used in the production of alcohol, wine-making and in baking bread.

QUESTION: 7

Which of the followings is also called sac fungi that live parasitically and in various habitats?

Solution:

Ascomycetes are called sac fungi that live parasitically and in various habitats. They are responsible for a number of fungal diseases in plants.

QUESTION: 8

On which of the following factors does the type of gas produced depend?

Solution:

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.

QUESTION: 9

First organic acid produced by microbial fermentation is _________.

Solution:
  • The first organic acid produced by microbial fermentation was lactic acid.
  • Lactic acid is produced by the anaerobic respiration of glucose.
QUESTION: 10

Vinegar is obtained from molasses with the help of:

Solution:

Vinegar is chemically diluted acetic acid which is produced by fermentation molasses in presence of Yeast and Acetobacter.

QUESTION: 11

Treatment of wastewater is done by:

Solution:
  • 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
QUESTION: 12

Which of the following crop has been developed by genetic engineering in India?

Solution:
  • 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. 
  • Bt-cotton is one such example, which is being cultivated in some states of our country.
QUESTION: 13

Which of the following is not correct regarding the primary treatment of wastewater?

Solution:
  • In primary treatment, initially floating debris is removed by sequential filtration.
  • Then grit and small pebbles are removed by sedimentation.
  • All solids that settle form the primary sludge while the supernatant forms the effluent.
    So the correct answer is 'A'.
QUESTION: 14

Which of the followings is mainly produced by the activity of anaerobic bacteria on sewage?

Solution:
  • 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 highly flammable.
    Thus, the correct answer is option D.
QUESTION: 15

Secondary treatment of sewage is also called _________.

Solution:

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

QUESTION: 16

High value of BOD shows?

Solution:
  • 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.
QUESTION: 17

Which of the following is a gram-negative bacterium?

Solution:

Escherichia coli is a gram-negative bacterium. The bacterium that does not retain the gram stain is called gram-negative bacteria.

QUESTION: 18

The common nitrogen-fixer in paddy fields is _________.

Solution:
  • 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.
QUESTION: 19

The most important of the symbiotic nitrogen-fixing bacteria which forms nodules on the roots of legume plants is _________.

Solution:

Rhizobium is a nitrogen-fixing bacteria found in the nodule of a leguminous plant's root. It increases the fertility of the soil.

QUESTION: 20

Which of the following organisms not fix atmospheric nitrogen?

Solution:
  • Spirogyra is a filamentous alga. This alga does not fix atmospheric nitrogen.
  • Anabaena, Nostoc and Oscillatoria can fix atmospheric nitrogen.
QUESTION: 21

Organisms called Methanogens are most abundant in a _________.

Solution:
  • Methanogen belongs to the Archaebacteria group. They are capable of producing methane gas or marshy gas or biogas.
  • They produce methane gas in marshy areas. They are most abundant in marshy areas and cattle yard where cow sheds are present. The methane gas produces a peculiar odour in these areas. Thus, the correct answer is 'Cattle yard.'
QUESTION: 22

Baculoviruses are pathogens that:

Solution:
  • Baculoviruses are pathogens that attack insects and other arthropods.
  • The majority of baculoviruses used as biological control agents falls under the genus Nucleopolyhydrovirus.
QUESTION: 23

Assertion: Biofertilizers are organisms that enrich the nutrient quality of the soil.
Reason: Organic farming is the farming technique in which no chemical is used as fertilizers or insecticides.

Solution:

Both assertion and reason are correct statements but the reason is not the correct explanation of the assertion. So option D is correct.

QUESTION: 24

The main source of bio-fertilizers is/are:

Solution:

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

QUESTION: 25

In which of the following microbes are not used extensively?
I. Converting milk into curd.
II. Making cheese of different flavour and taste.
III. Production of anti-viral drugs.
IV. Production of antibiotics.
V. As bio-fertilizers.
VI. Production of inorganic fertilizers.

Solution:
  • 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.

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