FREE NEET Biology Practice MCQ Test: Microbes In Human Welfare Exercise 4 Questions Answers With Detailed Explanations [PDF]

Answer: (c)

Methanogens are microorganisms that produce methane as a metabolic byproduct in anoxic conditions. They are obligate anaerobic ancient and primitive bacteria. They are involved in methanogenesis.

Answer: (a)

Trichoderma species are free-living fungi that are very common in root ecosystems or soil. These are effective biocontrol agents of several plant pathogens.

Answer: (b)

Primary treatment of sewage is a physical process and concerned mainly with the removal of coarse solid materials through filtration and sedimentation.

Answer: (c)

Answer: (c)

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, non-methanogenic and methanogenic. Methanogenic bacteria produce a mixture of gases containing methane, $H_2$S and $CO_2$.

Answer: (c)

Answer: (b)

Human insulin is being commercially produced from a transgenic species of Escherichia Coli. E.coli is a bacterium that is commonly found in the lower intestine of warm blooded animals.

Answer: (a)

Lactobacillus produce acids that coagulate and digest milk proteins.

Answer: (d)

Answer: (a)

In the secondary treatment of sewage, if oxygen availability to activated sludge flocs (masses of bacteria associated with fungal filaments to form mesh like structure) is reduced; the centre of flocs will becomes anoxic, which would cause death of bacteria and eventually breakage of flocs.

Answer: (a)

Primary treatment is a physical process which involves two process, i.e. filtration and sedimentation of big solid waste.

Answer: (a)

The control of insect pests by the introduction, encouragment and artificial increase of biological agencies like predaceous and parasitic insects, other animals and diseases is termed as biological control. It is basically a natural control in which man plays significant role of making the biological agencies more effective. Of these agencies, insect enemies play important role in nature for managing the phytophagous insect pests and keep a balance e.g., lady bugs or praying mantis, frog, toads, lizard and birds are employed by man to eat up the insect pests like aphids. It is a self perpetuating method.

Answer: (d)

Answer: (b)

Extensive growth of Opuntia (Cactus) in Australia was checked through introduction of its natural herbivore, cochineal insect (Cactoblastis cactorum).

Answer: (a)

Answer: (c)

Answer: (d)

Clostridium butylicum is used for butyric acid production

Answer: (d)

A common biocontrol agent for control of plant diseases is Trichoderma. Trichoderma is a free-living fungus that exerts biocontrol over several plant pathogens for the control of plant diseases. It is the natural method of pest and pathogen control.

Answer: (b)

Citric acid is obtained through the fermentation carried out by Aspergillus niger on sugary syrups. Citric acid is employed in dyeing, engraving, medicines, inks, flavouring and preservation of food and candies.