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CBSE Questions for Class 12 Medical Biology Microbes In Human Welfare Quiz 2 - MCQExams.com
CBSE
Class 12 Medical Biology
Microbes In Human Welfare
Quiz 2
The major gas in biogas production is ___________.
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Methane
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Carbon dioxide
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Hydrogen
0%
Nitrogen
Which of the following microorganisms is used as a biofertilizer?
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Bacillus
0%
Azospirillum
0%
Pseudomonas
0%
Saccharomyces
Which of the following act as a biofertilizers?
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Blue-green algae
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Green algae
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Yellow algae
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Red algae
Microbe used for biocontrol of pest butterfly caterpillars is?
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$$Bacillus$$ $$thuringiensis$$
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$$Streptococcus$$ species
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$$Trichoderma$$ species
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$$Saccharomyces$$ $$cerevisiae$$
Explanation
$$Bacillus$$ $$thuringiensis$$ are regarded as excellent biocontrol agents for butterfly caterpillars and hence used as a bioinsecticide.
Correct answer-A
The residue left after methane production from cattle dung is:
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burnt
0%
burned in land fills
0%
used as manure
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used In, civil construction
Explanation
The residue left after methane production from cattle dung is used as manure because it supply some organic materials and minerals to the soil.
So, the correct answer is 'used as manure'
A sewage treatment process in which a part of decomposer bacteria present in the wastes is recycled into the starting of the process is called as:
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primary treatment
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activated sludge treatment
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tertiary treatment
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none of these.
Explanation
A sewage treatment process in which a part of decomposer bacteria present in the wastes is recycled into the starting of the process is called activated sludge treatment .
So, the correct option is 'activated sludge treatment'
Statement 1 : Biocontrol refers to the use of biological methods for controlling plant diseases and pests.
Statement 2 : Use of biocontrol measures will greatly reduce our dependence on toxic chemicals and pesticides.
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Both statements 1 and 2 are correct.
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Statement 1 is correct but statement 2 is incorrect.
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Statement 1 is incorrect but statement 2 is correct.
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Both statements 1 and 2 are incorrect.
Explanation
Biocontrol refers to the use of biological methods for controlling plant diseases and pests.
Use of biocontrol measures will greatly reduce our dependence on toxic chemicals and pesticides.
So, the correct option is 'Both statements 1 and 2 are correct'
Biofertilisers are the living organisms which.
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bring about soil nutrient enrichment
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maximise the ecological benefits
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minimise the environmental hazards
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all of these
Explanation
Biofertilisers are living micro organisms which bring about soil nutrient enrichment,
maximise the ecological benefits,
minimise the environmental hazards.
So, the correct option is 'all of these'
First antibiotic discovered was ____________.
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Penicillin
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Ampicillin
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Celin
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Erythrocin
Explanation
The first antibiotic discovered was penicillin. It was discovered in 1928 by Alexander Fleming when he noticed the growth of mould-fungi in the culture of
Staphylococcus
and there were no bacteria in the region where the fungi were growing. It was because the fungi were secreting the chemical that had killed the bacterial cells in the culture. The fungus was recognized as
Penicillium
.
Hence, the correct answer is 'Penicillin'.
Sewage water can be purified for recycling with the action of
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Non-biodegradable chemicals
0%
Penicillin
0%
Microorganisms
0%
Fishes
Explanation
Sewage pollution can be prevented by treating sewage before passing into the watercourse, in sewage or effluent treatment plants (ETP).
The sewage is treated in ETP in three stages.
Stage one is Primary Treatment which comprises physical processes like sedimentation.
The second stage is aerobic and anaerobic biological degradation by microorganisms.
The last or tertiary stage is physicochemical degradation for removing turbidity and dissolved substances.
So, the correct answer is option C.
Azolla
is used as a biofertilizer because
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Azolla
multiplies very fast to produce massive biomass.
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Azolla
has association with nitrogen-fixing
Rhizobium
.
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Azolla
has association of nitrogen fixing cyanobacteria.
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Azolla
has association of mycorrhiza.
Explanation
Azolla
is used as a biofertilizer and it is known to contribute 40-60 kg N/ha per crop.
Azolla
is a pteridophyte and is used as a biofertilizer because it has association with nitrogen-fixing cyanobacteria
Anabaena azollae
.
Azolla-Anabaena
symbiotic system is the main biofertilizer inoculated in rice fields in South-Eastern Asia to increase yield up to 50%.
So, the correct answer is option C.
Which of the following symbiotic association is useful as biofertilizer?
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Rhizobium
and leguminous roots
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Azolla
and
Anabaena
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Both A and B
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None of the above
Explanation
Biofertilizers are organisms that enrich the nutrient quality of soil. The main sources of biofertilizers are bacteria, fungi, and cynobacteria (blue-green algae). The most striking relationship that these have with plants is symbiosis, in which the partners derive benefits from each other. Plants have a number of relationships with fungi, bacteria, and algae, the most common of which are with mycorrhiza, rhizobium, and cyanophyceae. These are known to deliver a number of benefits including plant nutrition, disease resistance, and tolerance to adverse soil and climatic conditions. These techniques have proved to be successful biofertilizers, that form a healthy relationship with the roots. Examples of symbiotic association used as a biofertilizers are Rhizobium and leguminous roots, Azolla and Anabaena etc.
Product of which of the following organisms has been commercialized as blood cholesterol lowering agent?
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Trichoderma polysporum
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Saccharomyces cerevisiae
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Aspergillus niger
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Monascus purpureus
Explanation
Trichoderma polysporum
i
s the
fungus used for commercial production of Cyclosporin A, which is used as an immunosuppressive agent in organ-transplant patients.
Saccharomyces cerevisiae
, also known as baker's yeast is the most common yeast species in bread and in sourdoughs.
Aspergillus niger
is one of the most important fungi used to produce extracellular (food) enzymes and citric acid.
Red yeast rice is a Chinese fermented rice product that improves blood circulation by decreasing cholesterol and triglyceride levels in humans as it produces blood-cholesterol lowering agents called statins.
Monascus purpureus
is a fungus used in the production of red yeast rice.
So the correct answer is option D.
Biodegradable pollutant among the following is _______.
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Plastic
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Asbestos
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Sewage
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All of the above
Explanation
A degradable pollutant is a pollutant, which degrades after some time either automatically (e.g., by heat) or through the agency of microorganisms e.g., sewage, livestock wastes, garbage, etc.
The wastewater generated from the homes and factories is known as 'Sewage' which is rich in organic substances and thus biodegradable.
So, the correct answer is option C.
When a natural predator applied on the other pathogenic organisms to control them, this process is called as
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Biological control
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Genetic engineering
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Confusion technique
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Artificial control
Explanation
Biological control is a component of an integrated pest management strategy.
Biological control is keeping the population of organisms or harmful pests and weeds under check by means of natural predators and
parasites.
so, the correct answer is '
Biological control'.
Stoppage of reproduction in an organism by creating hurdle in its biology or physiology or its destruction by use of another organism is known as
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Predation
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Competition
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Biological control
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Physiological control
Explanation
Biological control is keeping the population of an organism or harmful pests and weeds under check by means of natural predators, parasites, and amensals.
Trichoderma
species are free-living fungi found in the root ecosystem these are effective as biocontrol agents of several plant pathogens.
The bacteria which belong to the genus
Coccobacillus
are comparatively more pathogenic to insects and hence used for biological control.
So, the correct answer is '
Biological control'.
Antibiotic inhibits the growth or kills
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Bacteria
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Fungi
0%
Virus
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Both A and B
Explanation
A chemical substance or toxins produced by organisms such as bacteria or fungi is used to kill or reduce the growth of other pathogenic organisms such as bacteria and fungi, known as an antibiotic. It interferes with a particular step of cellular metabolism, causing either bactericidal or bacteriostatic inhibition. These are also called antimicrobial agents. Certain antibiotics destroy the bacteria and fungi by the disintegration of the bacterial and fungal cell walls. Some of the antibiotics inhibit DNA replication or translation of proteins.
Thus, the correct answer is option D.
The common Nitrogen-fixer in paddy fields is
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Frankia
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Rhizobium
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Azospirillum
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Oscillatoria
Explanation
Azospirillum
is a microaerophilic nitrogen fixer commonly found in association with the roots of cereals and grasses of interest.
It colonizes the root mass and fixes nitrogen in association with plants.
It is the popular nitrogen-fixer used in paddy fields along with
Azolla
. When a small amount of it is added to the soil, it multiplies into million and is capable of providing up to 20-40kg of nitrogen per hectare per season.
So, the correct answer is '
Azospirillum
'
Some blue green algae can be used as biofertilizer as they are
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Photosynthetic
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Surrounded by mucilage
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Growing every where
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Capable of fixing nitrogen
Explanation
Some blue-green algae can fix atmospheric nitrogen because they contain an O$$_{2}$$ sensitive enzyme nitrogenase. They live in close association with the roots of the plant and fix the atmospheric nitrogen into the soluble form which is utilized by the plant.
So, the correct answer is option D.
Trichoderma harzianum
has proved a useful microorganism for?
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Gene transfer in higher plants
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Biological control of soil-borne plant pathogens
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Bioremediation of contaminated soils
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Reclamation of wastelands
Explanation
Trichoderma harzianum
is an effective biocontrol agent against several fungal soil-borne plant pathogens.
They have an inhibitory effect on the growth of the mycelium of
Phytium
. They suppress the growth of fungi in order to allow the plant to grow favorably.
However, possible adverse effects of
T. harzianum
on plant growth-promoting microorganisms, such as arbuscular mycorrhiza (AM) fungi, might be a drawback in the use of this biocontrol agent in plant protection.
So, the correct answer is '
Biological control of soil-borne plant pathogens
Organic farming is the technique of raising crops through use of
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Manures
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Genetically modified seeds
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Biofertilizers
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Both A and C
Explanation
Organic farming is a system that involves those practices which maintain the natural fertility of the soil.
It avoids or largely excludes the use of fertilizers, pesticides, hormones, feed additives and relies upon crop rotations, crop residues, animal manures, off-farm organic waste, mineral grade rock additives, and a biological system of nutrient mobilization and plant protection.
Organic farming does not use plants or seeds with genetic modifications.
So, the correct answer is option D.
Mycorrhiza is a symbiotic association between
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Bacteria and fungi
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Algae and fungi
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Fungi and roots of higher plants
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Blue green algae and roots of higher plants.
Explanation
Mycorrhiza is the association of fungi and the roots of plants. It is a
symbiotic association where fungus helps in increasing the surface area of absorption. The mycorrhiza fungi help in the mineral uptake for the plant. The plant provides shelter and protection to the fungus. The fungus also obtains sugars from the plant.
Thus, the correct answer is option C.
$$Trichoderma$$
species are potentially useful as
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Biopesticides
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Biofertilizers
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Methanogens
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Vectors for genetic engineering
Explanation
$$Trichoderma$$ is a genus of fungi. It is used to treat seeds and soils to eliminate pathogens. These species have long been recognized as biological agents to control plant diseases.
The first application of these species was in the 1930s. Since then,
$$Trichoderma$$
species became a popular biological agent to protect crops against plant pathogens all over the world.
So, the correct answer is option A.
Biofertilizers include
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Nitrogen-fixing bacteria
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Nitrogen-fixing cyanobacteria
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Both bacteria and cyanobacteria
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Bacteria, cyanobacteria and mycorrhizal fungi
Explanation
The term biofertilizers or microbial inoculants may be used to include all organic resources (manure) for plant growth which are rendered in an available form for plant absorption through microorganisms or plant associations or interactions.
Biofertilizers are of three types, nitrogen-fixing bacteria, nitrogen-fixing cyanobacteria, and mycorrhiza.
So, the correct answer is option D.
Which of the following can be controlled by using biopesticides?
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Insects
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Diseases
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Weeds
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All of the above
Explanation
Biopesticides are biochemical pesticides that are naturally occurring substances that control pests like insects and weeds by nontoxic mechanisms.
It is made up of
living organisms or its product to manage the pests that are injurious to plants.
They pose less threat to the environment and humans.
Biopesticide also controls the spread of disease by killing the causing organisms.
These include biofungicides (
Trichoderma
), bioherbicides (
Phytophthora
) and bioinsecticides
(Bacillus thuringiensis).
Thus, the correct answer is option D.
One of the major difficulties in the biological control of insect pests is that
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The predator develops a preference to other diets and may itself become a pest.
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The predator does not always survive when transferred to a new environment.
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The method is less effective as compared with the use of insecticides.
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The practical difficulty of introducing the predator to specific areas.
Explanation
Biological control is not a quick fix for most pest problems.
Biological control can be fickle. While it's supposed to manage one pest, there is always the possibility that predators will switch to a different target as they might decide to eat crops instead of the insects infesting them.
I
ntroducing a new species to an environment, there runs the risk of disrupting the natural food chain.
It is a slow process and takes a lot of time and patience for the biological agents to work their magic on a pest population.
Predators can only survive if there is something to eat, so destroying their food population would risk their own safety.
Therefore, they can only reduce the number of harmful pests.
While it is cheap in the long run, the process of actually setting up a biological control system is a costly endeavor.
A lot of planning and money goes into developing a successful system.
Thus, the correct answer is option A.
Yield of paddy field can be increased by application of
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Iron bacteria
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Nostoc/Anabaena
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Archae bacteria
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Symbiotic bacteria
Explanation
Blue-green algae are ideally suited for propagation in rice fields because blue -green algae form a self-sufficient system which is capable of fixing atmospheric nitrogen in organic forms and which grows upon a free water surface. It
increases nitrogen content of moist soil and water bodies, which can be used in increasing paddy yield
So, the correct answer is
'
Nostoc/Anabaena'
Leghaemoglobin occurs in
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Coralloid root
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Blue green algae
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Around bacteriods
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Mycorrhiza
Explanation
A single enlarged, non - motile bacterium is referred to as bacteroids. These results in proliferation of tissues, which eventually results in forming a root nodule. A typical root nodule contains several thousand bacteroids. The nodule contains a protein called leghemoglobin which gives nodules a pink color.
Thus, the correct answer is option C.
Azolla
is used as biofertilizer as it has
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Rhizobium
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Cyanobacteria
0%
Mycorrhiza
0%
Large quantity of humus
Explanation
Azolla
is used as a biofertiliser because the leaves of this plant have cyanobacteria called
Anabaena.
This is an algae which have the enzyme nitrogenase in the heterocysts. The heterocysts are specialized cells in the algae. These cells help in fixation of nitrogen with the help of the enzyme. The rice plants grown in these paddy fields use this fixed nitrogen. Thus, the yield is increased.
Thus, the correct answer is option B.
Which one is a biofertilizer?
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VAM
0%
Sporeine
0%
Devine
0%
Agent Orange
Explanation
VAM (Vesicular-arbuscular mycorrhizae) is formed by the symbiotic association between certain phycomycetous fungi and angiosperm roots. The fungus absorbs the water and nutrients from the soil and provides them to the plant while the angiosperms provide the prepared food to the fungi.
So, the correct answer is option A.
Most famous nitrogen fixing bacterium/biofertilizer is
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Nitrobacter
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Nitrosomonas
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Nitrococcus
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Rhizobium
Explanation
Rhizobium is the most well-known species of a group of bacteria that acts as the primary symbiotic fixer of nitrogen. These bacteria can infect the roots of leguminous plants, leading to the formation of lumps or nodules where the nitrogen fixation takes place.
So, the correct answer is '
Rhizobium'.
Which of the following statements is correct?
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Legumes fix nitrogen through bacteria in their leaves
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Legumes fix nitrogen through bacteria in their roots
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Legumes fix nitrogen independent of bacteria
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Legumes do not fix nitrogen
Explanation
Leguminous plants in association with the bacteria in their root nodules can fix atmospheric nitrogen in the soil. The nitrogen can be fixed with the help of nitrogenase enzyme. The nitrogen is fixed and converted into forms of nitrates. The nitrates can be easily taken up by the plant roots. The increased nitrogen will help in the growth of succeeding crops as well.
Thus, the correct answer is option B.
Mycorrhiza represents
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Antagonism
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Endemism
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Symbiosis
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Parasitism
Explanation
Mycorrhiza is the symbiotic relationship between fungi and roots of the higher plants where fungi help in increasing the surface area of absorption. They also help in the mineral uptake by the plant in return plant provides protection and shelter and food to the fungi
So, the correct answer is '
Symbiosis'
Which one of the following is not biofertilizer?
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Mycorrhiza
0%
Agrobacterium
0%
Rhizobium
0%
Nostoc
Explanation
Agrobacterium
is a gene transfer agent.
Agrobacterium tumefaciens
causes crown gall disease of a wide range of dicotyledonous (broad - leaves) plants, especially members of the rose family such as apple, pear, peach, cherry, almond, raspberry, and roses.
So, the correct answer is option B.
Citric acid is produced by
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Aspergillus
0%
Pseudomonas
0%
Clostridium
0%
Saccharomyces
Explanation
Aspergillus
is a genus of fungi. The largest application of
Aspergillus niger
is as the major source of citric acid. The bacteria is useful for the commercial production of citric acid.
Thus, the correct answer is option A.
Clostridium acetobutylicum
helps in the production of
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Acetone
0%
Ethanol
0%
Butanol
0%
All of the above
Explanation
Clostridium acetobutylicum
is a commercially valuable bacterium. It produces acetone, ethanol, and butanol from starch at the same time.
So, the correct answer is 'All of the above'.
Which weed has been eradicated by biological control?
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Parthenium
0%
Cactus
0%
Eichhornia
0%
Chrysanthemum
Explanation
Cactus was the plant which had beautiful flowers and grows very rapidly. This property of the plant was used to decorate the fences or use the plant as hedges in agricultural land sand farms. The plant has been eradicated by the method of biological control. It was done by introducing the cochineal insect
Cactoblastis Cactorum
. The insect is a type of moth which exceptionally feeds on the cactus plant. Biological control is a method of controlling pests by using microbes and it is based on the the natural predation or parasitism.
Thus, the correct answer is option B.
Find out the pairs, which are correctly matched.
A. Cyanobacteria (i.) Biopesticides
B. Mycorrhiza (ii.) Solubilization of phosphate
C.
Bacillus thuringiensis
(iii.) Cry protein
D. Single-cell protein (iv.) Rhizobia
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A and ii.
0%
C and iii
0%
C and iv
0%
A and iii
0%
B and i
Explanation
Bacillus thuringiensis
(Bt) is commonly used as a biopesticide. It is sporulating, a gram-positive facultative-aerobic soil bacterium. It synthesizes the proteins known as delta endotoxins or cry proteins which infect the insects by paralyzing the digestive tract and makes it porous.
So, the correct answer is option B.
Rhizosphere is the region where ?
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Rhizobium forms root nodules
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Algae and root make contact
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Soil and root are in contact
0%
Bacterial and root nearly make contact
Explanation
The rhizosphere is the small region or zone of soil that is directly influenced by root secretions and associated soil microorganisms. It is an area of soil immediately surrounding the roots along with root surface. This region influences plant roots. A major characteristic of the rhizosphere is the release of organic compounds by plant roots
into the soil
. Due to this, the environment of rhizosphere is very much different from rest of the soil.
Thus, the correct answer is option C.
VAM is important for
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Breaking of dormancy
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Phosphate nutrition
0%
Water uptake
0%
Retarding flowering
0%
Decrease in yield
Explanation
Vesicular
-
arbuscular mycorrhiza
(VAM) is formed by the symbiotic association between certain phycomycetous fungi and angiosperm roots.
It improves plant growth through phosphorous nutrition. In addition to phosphorous, they also help in the uptake of other nutrient elements. Nutrient absorption by fungal symbionts is due to external hyphae of the fungus proliferating beyond the nutrient depletion zone and reaching the source of nutrients. Mycorrhizal fungi appear to be extremely advantageous to crops grown in soils with low fertility.
So, the correct answer is '
Phosphate nutrition'
Which of the following can use molecular nitrogen as nutrient?
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Methanomonas
0%
Mucor
0%
Rhizobium
0%
Spirogyra
Explanation
Rhizobium
fixes the nitrogen symbiotically. The nitrogen-fixing bacteria enter the roots and lead to the incessant growth of the cortical cells which form nodules that act as a primary site for the nitrogen fixation. The enzyme nitrogenase is primarily used for the conversion of molecular nitrogen.
So, the correct answer is option C.
Biofertilizers
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Kill pests
0%
Prevent pest growth
0%
Retain soil fertility
0%
All of the above
Explanation
Biofertilizers are used because they increase soil fertility, crop productivity, and production. Use of biofertilizers is both economical as well as environment-friendly. They remain symbiotically associated with the roots while some are free living. They solubilize the undissolved minerals.
So, the correct answer is option C.
Which one is a non-symbiotic nitrogen fixer?
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Rhizobium
0%
Anabaena
0%
Nostoc
0%
Bradyrhizobium
Explanation
Nostoc
is a
free-living
(non-symbiotic) autotrophic
C
yanobacteria
and used as
biofertilser
for wetland rice and can provide 25-30 kg nitrogen/
hectare
. The heterocysts are the sites of nitrogen fixation. Heterocyst formation occurs only in filamentous
Cyanobacteria
.
So, the correct answer is option C.
Latest trend in plant disease control is
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Chemical control
0%
Biological control
0%
Good manure and fertilizer
0%
Breeding for disease resistance
Explanation
Integrated pest management (IPM) is the programme which particularly focuses on agricultural crop diseases and its management. According to It, the use of b
iological control agent or other living organisms can control the plant diseases. Biological control is environment-friendly and effective against a broad range of insect pests and relatively easy to adopt.
So
, the correct answer is '
Biological control'
Leghaemoglobin takes part in
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Energy release
0%
Stimulating growth of
Rhizobium
0%
N$$_{2}$$ absorption
0%
Protecting nitrogenase
0%
Supply of oxygen
Explanation
The pink color, typical of healthy and effective nodules, is due to the presence of a protein called leghemoglobin. This special protein contains Iron (Fe) and molybdenum (Mo) and is responsible for binding oxygen. This provides sufficient oxygen for the metabolic functions of the
bacteroids but prevents the accumulation of free oxygen that would destroy the activity of nitrogenase.
So, the correct answer is option D.
Which of the following aquatic fern is an excellent bio fertilizer?
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Salvinia
0%
Azolla
0%
Marsilea
0%
Pteridium
Explanation
Azolla pinnata
is an aquatic fern, which contains a nitrogen-fixing cyanobacteria. It contains
Anabaena azollae
in its leaf cavities. It is an excellent biofertilizer for paddy fields because they can fix nitrogen in moist condition also.
Thus, the correct answer is option B.
A common biocontrol agent for the control of plant diseases is
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Trichoderma
0%
Baculovirus
0%
Bacillus thuringiensis
0%
Glomus
Explanation
Trichoderma species of fungi are commonly found in the soil. They form symbiotic associations with plants. They do not cause any infection or disease in plants but suppress the infection by other species of fungus.
The common species of
Trichoderma
are
T. herbarium
,
T. viridae
and
T
.
hamatum.
These species are popular biological agents to protect crops against plant pathogens, all over the world.
They are commonly used for root infections but can also be useful in preventing foliar disease.
Thus, the correct answer is option A.
Confusion technique uses
Report Question
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Juvenile hormone
0%
Ecdysone
0%
Pheromone
0%
A combination of hormones
Explanation
The aim of the confusion technique is to lay artificial pheromone trails or even to saturate the crop environment with the odour of synthetic pheromone, in order to confuse the males and prevent them from locating females. It is expensive and therefore not usually practical
So, the correct answer is '
Pheromone'
Which one of the following bacterial groups are exploited in biogas production?
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Methanogens
0%
Methanotrophs
0%
Organotrophs
0%
Eubacteria
Explanation
$$\textbf{Correct option:}$$ A
$$\bullet$$ Methanogens are the bacterial groups that are exploited in biogas production.
$$\textbf{Explanation:}$$
$$\bullet$$ Methanogens are prokaryotic organisms that produce methane as their metabolic by-product.
$$\bullet$$ They produce methane in two ways either by reducing the carbon dioxide with hydrogen or by converting acetic acid to methane and carbon dioxide.
$$\bullet$$ The process of methane formation is called methanogenesis.
$$\textbf{Additional information:}$$
$$\textbf{Organotrophs:}$$
$$\bullet$$ Organotrophs, including humans, fungi, and many prokaryotes, are chemotrophs that obtain energy from organic compounds.
$$\textbf{Eubacteria:}$$
$$\bullet$$ Eubacteria, or "genuine" microbes, are single-celled prokaryotic microorganisms mainly that have a scope of qualities and are found in different conditions all through all parts of the world.
$$\textbf{Methanotrophs :}$$
$$\bullet$$ Methanotrophs (sometimes called methanophiles) are prokaryotes that metabolize methane as their source of carbon and energy.
Which one is a biofertilizer
Report Question
0%
NPK mixture
0%
Rhizobia in legume roots
0%
Rhizobia in farmyard manure
0%
Green manure
Explanation
All cyanophyceae member's are biofertilizers because they has fixing of NZ e.g. Nostoc. Rebulla, Rhizobia etc.
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Practice Class 12 Medical Biology Quiz Questions and Answers
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