FREE NEET Biology Practice MCQ Test: Microbes In Human Welfare Exercise 3 Questions Answers With Detailed Explanations [PDF]

Answer: (c)

Answer: (a)

Answer: (a)

Organic farming includes serval methods to enhance soil fertility. In such farming, methods of biological origin are used e.g., biopesticides biofertilizers, IPM (Integrated Pest Management) green manure, bioherbicides etc. Chemical fertilizers are not used in organic farming.

Answer: (a)

Activated sludge microorganisms require oxygen as they oxidise wastes to obtain energy for growth. Insufficient oxygen will slow down or kill off aerobic to the breakage of flocs.

It may also result in the production of the foul-smelling by products of anaerobic decomposition, So, sufficient oxygen should always be maintained in the aeration tank to ensure complete waste stabilisation.

Answer: (b)

Answer: (b)

Biofertilizers are living organisms, which help in increasing the fertility of soil. Example includes Azolla and blue green algae.

Answer: (b)

This incorrect statement can be corrected as

Methanogens are present in the rumen (a part of stomach) of cattle (runminant) where it acts on the cellulosic content to yield a methane rich mixtrue of gases.

Rest of the statements are correct.

Answer: (d)

Answer: (d)

Answer: (b)

Answer: (c)

Microbial biocontrol agent that can be introduced in order to control butterfly caterpillars is the bacteria Bacillus thuringiensis (Bt). They are sprayed onto vulnerable plants, where they 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.

Answer: (c)

Answer: (a)

Answer: (c)

Aspergillus niger is used for the production of citric acid in industries. Citric acid is the most important organic acid and is extensively used in food and pharmaceutical industries. It is produced mainly by submerged fermentation using Aspergillus niger or Candida sp. from different sources of carbohydrates, such as molasses and starch based media.

Answer: (a)

A – III; B – IV; C – II; D – I

Answer: (c)

Zymase is an enzyme complex that catalyzes the fermentation of sugar into ethanol and carbon dioxide. It occurs naturally in yeasts. Its activity varies among yeast strains.

Answer: (a)

Bacteria develop mutant strains that become resistant to antibodies, so these antibodies become incapable of removing bacteria mediated diseases.

Answer: (c)

This incorrect statement can be corrected as

Certain bacteria, which grow anaerobically on cellulosic material, produce large amount of methane along with $CO_2$ and $H_2$ .

These bacteria are collectively called methanogens and one such example is Methanobacterium.

Rest of the statements in other options are correct.

Answer: (c)

Sewage water can be purified by passing it through sewage treatment plants with the action of heterotrophic microorganisms. There are three stages of this treatment – primary, secondary and tertiary. Primary treatment removes floating and suspended solids from sewage through two processes of filtration and sedimentation. First floating matter is removed through sequential filtration.

The filtrate is kept in large open settling tanks where grit settles down. The sediment is called primary sludge while the supernatant is called effluent. The primary sludge traps a lot of microbes and debris. In secondary treatment, the primary effluent is taken to aeration tanks. A large number of aerobic heterotrophic microbes grow in the aeration tank. They form flocs. Flocs are masses of bacteria held together by slime and fungal filaments to form mesh like structures.

The microbes digest a lot of organic matter, converting it into microbial biomass and releasing a lot of minerals. As the BOD of the waste matter is reduced to 10-15% of raw sewage, it is passed into settling tank. Thus secondary treatment is more or less biological. The sediment of settling tank is called activated sludge. The remaining is passed into a large tank called anaerobic sludge digester. It is designed for continuous operation. The aerobic microbes present in the sludge get killed.

Anaerobic microbes digest the organic mass as well as aerobic microbes of the sludge. They are of two types, nonmethanogenic and methanogenic. Methanogenic bacteria produce a mixture of gases containing methane, $H_2 S$ and $CO_2$ .

Answer: (c)

Probiotics are live microorganisms (bacteria in most cases) that are similar to beneficial microorganisms found in the human gut. They are also called "friendly bacteria" or " good bacteria". Probiotic microorganisms consist mostly of strains of Lactobacillus, Bifidobacterium and Streptococcus. Probiotics are taken as food supplement and energy drinks (e.g. Yakult).