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455 questions in this collection · Page 8 of 46
Question 71 of 455
📘 CLASS XII
Microbes In Human Welfare
What is the primary benefit derived by the fungus from its symbiotic mycorrhizal association with a plant?
The fungus, as a heterotroph, benefits from the association by deriving nutrients from the plant; this is implied as the plant receives P and protection.
Question 72 of 455
📘 CLASS XII
Microbes In Human Welfare
According to the text, which category of life forms constitutes major components of biological systems on Earth, besides macroscopic plants and animals?
Besides macroscopic plants and animals, microbes are the major components of biological systems on this earth.
Question 73 of 455
📘 CLASS XII
Microbes In Human Welfare
Which of the following environments is cited as a location where microbes are present, even though other life-forms could not possibly exist?
They are present even at sites where no other life-form could possibly exist, such as in highly acidic environments.
Question 74 of 455
📘 CLASS XII
Microbes In Human Welfare
LAB (Lactic Acid Bacteria) play a beneficial role in the human stomach by:
In our stomach too, the LAB play very beneficial role in checking disease-causing microbes.
Question 75 of 455
📘 CLASS XII
Microbes In Human Welfare
Which bacterium is responsible for the production of Lactic acid?
Lactobacillus (a bacterium) is an example of a producer of lactic acid.
Question 76 of 455
📘 CLASS XII
Microbes In Human Welfare
The effluent from the primary settling tank proceeds directly to which stage of sewage treatment?
The effluent from the primary settling tank is taken for secondary treatment.
Question 77 of 455
📘 CLASS XII
Microbes In Human Welfare
What must be constantly done to the primary effluent in the large aeration tanks during secondary treatment?
The primary effluent is passed into large aeration tanks where it is constantly agitated mechanically and air is pumped into it.
Question 78 of 455
📘 CLASS XII
Microbes In Human Welfare
The BOD value of three water samples (A, B, C) were 20 mg/L, 8 mg/L, and 400 mg/L respectively. Which sample is considered the most polluted?
The greater the BOD of waste water, more is its polluting potential. Sample C has the highest BOD (400 mg/L).
Question 79 of 455
📘 CLASS XII
Microbes In Human Welfare
Assuming river water is relatively clean, which sample (A: 20 mg/L, B: 8 mg/L, C: 400 mg/L) likely represents the secondary effluent discharge?
Untreated sewage (C: 400 mg/L) is most polluted. River water (B: 8 mg/L) is least polluted. Secondary effluent (A: 20 mg/L) has reduced BOD but is higher than clean river water.
Question 80 of 455
📘 CLASS XII
Microbes In Human Welfare
The gases produced during anaerobic digestion of activated sludge, particularly methane, are used as a source of energy because the gas mixture is:
These gases form biogas and can be used as source of energy as it is inflammable.