FREE NEET Biology Practice MCQ Test: Microbes In Human Welfare Exercise 1 Questions Answers With Detailed Explanations [PDF]

Answer: (c)

Answer: (b)

Streptokinase are produced by Streptococcus and are used as a ‘clot buster’ to remove clots from the blood vessels of patients who have myocardial infarction.

Answer: (b)

Answer: (b)

Answer: (a)

Bacillus thuringiensis is the most effective biocontrol agent for insect pests such as butterfly caterpillars. Spores of this bacterium produce a toxic insecticidal protein called Cry. These proteins enter the host's body and reach gut where on activation they kill the host by lysis.

Answer: (d)

Anabaena is a free living nitrogen fixing cyanobacterium which can form symbiotic association with the water fern Azolla.

Answer: (d)

Answer: (d)

Answer: (c)

Assertion is true, but Reason is false. Reason can be corrected as

Leguminous crops are grown in rotation of crops. These plants have the ability to fix atmospheric nitrogen to form nitrogen compounds through the help of certain bacteria, like Rhizobium, present in their root nodules. In rotation of crops, leguminous crops like pulses, beans, peas, groundnut and Bengal gram are sown in between the seasons of cereal crops like wheat, maize and pearl millet. These are leguminous plants when grown alternately with non-leguminous plants restore the fertility of the soil.

Answer: (c)

In the biological treatment of sewage, flocs are formed. These are masses of bacteria associated with fungal filaments to form a mesh-like structure. The growing microbes consume organic matter and thus reduce the Biochemical Oxygen Demand (BOD) and lowers the level of pollutants.

Answer: (a)

Answer: (c)

Primary treatment does not involve microbes. It is the physical removal of large and small particles from sewage.

However, secondary treatment of the effluent from the primary settling tank is purely a biological treatment involving microbial activity. Further, in the anaerobic sludge digesters, heterotrophic microbes anaerobically digest bacteria and fungi in the sludge producing mixture of gases such as methane, hydrogen sulphide and $CO_2$ , which form biogas.

Thus, microbes are used in secondary treatment, anaerobic sludge digesters and biogas production.

Answer: (c)

Answer: (b)

Answer: (b)

Answer: (c)

Answer: (a)

Besides cereals, green vegetables, brewer's yeast, egg white, vitamin B12 is also produced by intestinal bacteria. The vitamin was first obtained in 1938 using wild strain of mould Ashbhya gossypii. Vitamin B12 is essential for normal growth and reproduction in a number of laboratory animals.

Answer: (c)

Cyanobacteria (blue-green algae) is one of the major components of the nitrogen fixing biomass in the paddy (rice) field. The agricultural importance of cyanobacteria in rice cultivation is directly related with their ability to fix nitrogen and other positive effects for plants and soil.

Answer: (d)

Answer: (d)

The major component of biogas is methane (about 50-68%) which is highly inflammable . The other gases are carbon dioxide (25 - 35%), hydrogen (1 - 5%), nitrogen (2 - 7%), oxygen (0 - 0.1%) and rarely hydrogen sulfide. Biogas is a “mixture of gases” produced from degradable organic matter by the activity of various anaerobic bacteria that offers a low cost alternative for energy requirements.