FREE NEET Biology Practice MCQ Test: Microbes In Human Welfare Exercise 2 Questions Answers With Detailed Explanations [PDF]

Answer: (b)

A biological control being developed for use in the treatment of plant disease is the fungus Trichoderma. Trichoderma species are free living fungi that are very common in the root ecosystems. They are effective biocontrol agents of several plant pathogens.

Answer: (c)

Primary or physical treatment is the process of removal of small and large, floating and suspended solids from sewage through two processes of filtration and sedimentation.

Answer: (a)

Answer: (d)

Answer: (d)

A good source of citric acid is Aspergillus niger (a fungus). Apart from citric acid, oxalic acid, gallic acid, and gluconic acid are extracted from fungus.

Answer: (c)

Answer: (b)

In the digesters (during secondary treatment of waste water), heterotrophic microbes like methanogens anaerobically digest biodegradable waste in sludge producing mixture of gases such as methane, hydrogen sulphide and $CO_$2 which form the biogas. Thus, $O_2$ is not produced by methanogens.

Answer: (a)

Rhizobium is used as a biofertilizer for raising leguminous crop. Rhizobium japonicum forms symbiotic association in the roots of the leguminous plant, soybean.

Answer: (d)

Answer: (c)

Answer: (d)

Organic farming involves use of organic wastes and other biological material along with beneficial microbes to release nutrients to crop to increase the soil fertility in an eco-friendly, and pollution free environment. Glomus, earthworm and Oscillatoria can be used in organic farming while snail cannot.

Answer: (d)

Pheromones are volatile chemicals produced by a given species to communicate with other individuals of the same species to change their behaviour. The synthetic versions of lepidopteran pheromones can be used as pesticides. Sometimes the relative amount of several pheromone chemicals in a pesticide product determine which specific pests are controlled when the pesticide product releases pheromone into the air where males are looking for females, the males become confused and cannot easily locate the females.

As a result, many of the females do not mate and lay eggs and there are many fewer offspring than usual. These insect pheromones are third generation pesticides. Other third generation pesticides are insect growth regulators, chitin synthesis inhibitors and juvenile hormones.

Answer: (b)

Answer: (b)

Thurioside is toxic to several insects and produced by bacterium Bacillus thuringiensis.

Answer: (d)

The natural method of pest and pathogen control involving use of viruses, bacteria and other insects (which are their natural predators and pests) is called biocontrol or biological control. For example, free living fungus Trichoderma exerts biocontrol over several plant pathogens for the control of plant diseases. Baculoviruses (mostly of genus Nucleopolyhedrovirus) are also used as biocontrol agents but they are used for the control of insects and arthropods. Bacillus thuringiensis is a soil bacterium which is used as biopesticide. Glomus species are the most common fungal partners of mycorrhiza residing in the roots of higher plants.

Answer: (c)

A biofertilizer is a substance which contains living microorganisms which, when applied to seed, plant surfaces, or soil, colonizes the rhizosphere or the interior of the plant and promotes growth by increasing the supply or availability of primary nutrients to the host plant. Cyanobacteria (blue green algae), symbiotic bacteria (Rhizobium, Anabaena) and free living bacteria (Azotobacter, Clostridium) are used as biofertilizer. Yeast is a microscopic fungus which consists of single oval cells that reproduce by budding, and capable of converting sugar into alcohol and carbon dioxide.

Answer: (b)

Biofertilizers are organisms that enrich the nutrient quality of the soil. The main sources of biofertilizers are bacteria, fungi and cyanobacteria. Rhizobium bacteria is found in the nodules on the roots of leguminous plants by symbiotic association. These bacteria fix atmospheric nitrogen into organic forms, which is used by the plants as nutrient. Fungi are also known to form symbiotic associations with plants called mycorrhiza. Cyanobacteria are autotrophic microbes widely distributed in aquatic and terrestrial environments. Many of which can fix atmospheric nitrogen, e.g., Anabaena, Nostoc, Oscillatoria etc. But Agrobacterium tumefaciens is a pathogen of several dicot plants. It causes gall tumor in the plants.

Answer: (a)

Tissue plasminogen activator (TPA) is the enzyme that dissolve blood clots.

Answer: (a)

Answer: (a)

Probiotics are dietary supplements containing potentially beneficial bacteria or yeast, with lactic acid bacteria (LAB) as the most common microbes used. LAB have been used in the food industry for many years, because they are able to convert sugars (including lactose) and other carbohydrates into lactic acid. They not only provides the characteristic sour taste of fermented dairy foods such as yoghurt, but acts as a preservative, by lowering the pH and creating fewer opportunities for spoilage organisms to grow.