NEET AIPMT Biology Chapter Wise Solutions – Microbes in Human Welfare
Contents
1. Match the following list of microbes and their importance.
(a) A-(iv), B-(ii), C-(i), D-(iii)
(b) A-(iii), B-(i), C-(iv), D-(ii)
(c) A-(iii), B-(iv), C-(i), D-(ii)
(d) A-(iv), B-(iii), C-(ii),D-(i) (AIPMT 2015)
2. The guts of cow and buffalo posses
(a) Methanogens
(b) Cyanobacteria
(c) Fucus sp.
(d) Chlorella sp. (AIPMT2015, Cancelled)
3. Which one of the following fungi contains hallucinogens?
(a) Morchella esculenta
(b) Amanita muscaria
(c) Neurospora sp.
(d) Ustilago sp. (AIPMT 2014)
4. An alga which can be employed as food for human being is
(a) Ulothrix
(b) Chlorella
(c) Spirogyra
(d) Polysiphonia. (AIPMT 2014)
5. What gases are produced in anaerobic sludge digesters?
(a) Methane and C02 only
(b) Methane, Hydrogen sulphide and C02
(d) Methane, Hydrogen sulphide and 02
(d) Hydrogen sulphide and C02 (AIPMT 2014)
6. A good producer of citric acid is
(a) Clostridium
(b) Saccharomyces
(c) Aspergillus
(d) Pseudomonas. (NEET 2013)
7. Microbe used for biocontrol of pest butterfly caterpillars is
(a) Saccharomyces cerevisiae
(b) Bacillus thuringiensis
(c) Streptococcus sp.
(d) Trichoderma sp. (Karnataka NEET 2013)
8. Monascus purpureus is a yeast used commercially in the production of
(a) ethanol
(b) streptokinase for removing clots from the blood vessels
(c) citric acid
(d) blood cholesterol lowering statins. (Prelims 2012)
9. A patient brought to a hospital with myocardial infarction is normally immediately given
(a) penicillin
(b) streptokinase
(c) cyclosporin-A
(d) statins. (Prelims 2012)
10. A nitrogen-fixing microbe associated with Azolla in rice fields is
(a) Spirulina
(b) Anabaena
(c) Frankia
(d) Tolypothrix. (Prelims 2012)
11. Which one of the following is an example of carrying out biological control of pests/diseases using microbes?
(a) Trichoderma sp. against certain plant pathogens.
(b) Nucleopolyhedrovirus against white rust in Brassica.
(c) Bt-cotton to increase cotton yield.
(d) Lady bird beetle against aphids in mustard. (Prelims 2012)
12. In gobar gas, the maximum amount is that of
(a) butane
(b) methane
(c) propane
(d) carbon dioxide. (Mains 2012)
13. Read the following four statements (A – D).
(A) Colostrum is recommended for the new bom because it is rich in antigens.
(B) Chikungunya is caused by a Gram negative bacterium.
(C) Tissue culture has proved useful in obtaining virus-free plants.
(D) Beer is manufactured by distillation of fermented grape juice.
How many of the above statements are wrong?
(a) Two
(b) Three
(c) Four
(d) One. (Mains 2012)
14. The domestic sewage in large cities
(a) has a high BOD as it contains both aerobic and anaerobic bacteria
(b) is processed by aerobic and then anaerobic bacteria in the secondary treatment in Sewage Treatment Plants (STPs)
(c) when treated in STPs does not really require the aeration step as the sewage contains adequate oxygen
(d) has very high amount of suspended solids and dissolved salts. (Mains 2012)
15. Consider the following four statements (A – D) and select the option which includes all the correct ones only.
(A) Single cell Spirulina can produce large quantities of food rich in protein, minerals, vitamins etc.
(B) Body weight-wise the microorganism Methylophilus methylotrophus may be able to produce several times more proteins than the cows per day.
(C) Common button mushrooms are a very rich source of vitamin C.
(D) A rice variety has been developed which is very rich in calcium.
(a) Statements (C) and (D)
(b) Statements (A), (C) and (D)
(c) Statement (B), (C) and (D)
(d) Statement (A) and (B). (Mains 2012)
16. The most common substrate used in distilleries for the production of ethanol is
(a) com meal
(b) soya meal
(c) ground gram
(d) molasses. (Prelims 2011)
17. Which one of the following is not a biofertilizer?
(a) Agrobacterium
(b) Rhizobium
(c) Nostoc
(d) Mycorrhiza (Prelims 2011)
18. Secondary sewage treatment is mainly a
(a) physical process
(b) mechanical process
(c) chemical process
(d) biological process (Prelims 2011)
19. Which of the following is mainly produced by the activity of anaerobic bacteria on sewage?
(a) laughing gas
(b) propane
(c) mustard gas
(d) marsh gas (Prelims 2011)
20. An organism used as a biofertilizer for raising soyabean crop is
(a) Azotobacter
(b) Azospirillum
(c) Rhizobium
(d) Nostoc. (Prelims 2011)
21. Ethanol is commercially produced through a particular species of
(a) Saccharomyces
(b) Clostridium
(c) Trichoderma
(d) Aspergillus. (Prelims 2011)
22. Continuous addition of sugars in ‘fed batch’ fermentation is done to
(a) produce methane
(b) obtain antibiotics
(c) purify enzymes
(d) degrade sewage. (Prelims 2011)
23. Organisms called methanogens are most abundant in a
(a) sulphur rock
(b) cattle yard
(c) polluted stream
(d) hot spring. (Prelims 2011)
24. Read the following statement having two blanks (A andB).
“A drug used for A patients is obtained from a species of the organism B .
The one correct option for the two blanks is
25. Consider the following statements (A-D) about organic farming.
(A) Utilizes genetically modified crops like Bt cotton.
(B) Uses only naturally produced inputs like compost.
(C) Does not use pesticides and urea.
(D) Produces vegetables rich in vitamins and minerals.
Which of the above statements are correct?
(a) B, C and D
(b) C and D only
(c) B and C only
(d) A and B only (Mains 2011)
26. Which one of the following is a wrong matching of a microbe and its industrial product, while the remaining three are correct?
(a) Yeast – statins
(b) Acetobacter aceti – acetic acid
(c) Clostridium butylicum – lactic acid
(d) Aspergillus niger – citric acid (Mains 2011)
27. Select the correct statement from the following
(a) biogas is produced by the activity of aerobic bacteria on animal waste
(b) Methanobacterium is an aerobic bacterium found in rumen of cattle
(c) biogas, commonly called gobar gas, is pure methane
(d) activated sludge-sediment in settlement tanks of sewage treatment plant is a rich source of aerobic bacteria. (Prelims 2010)
28. A common biocontrol agent for the control of plant diseases is
(a) baculovirus
(b) Bacillus thuringiensis
(c) Glomus
(d) Trichoderma. (Prelims 2010)
29. The common nitrogen-fixer in paddy fields is
(a) Rhizobium
(b) Azospirillum
(c) Oscillatoria
(d) Frankia. (Prelims 2010)
30. Which one of the following is not used in organic farming?
(a) Glomus
(b) earthworm
(c) Oscillatoria
(d) snail. (Prelims 2010)
31. An example of endomycorrhiza is
(a) Nostoc
(b) Glomus
(c) Agaricus
(d) Rhizobium. (Mains 2010)
32. Which one of the following pairs is wrongly matched?
(a) alcohol – nitrogenase
(b) fruit juice – pectinase
(c) textile – amylase
(d) detergents – lipase (Prelims 2009)
33. Which ofthe following is not used as a biopesticide?
(a) Trichoderma harzianum
(b) nuclear polyhedrosis virus (NPV)
(c) Xanthomonas campestris
(d) Bacillus thuringiensis (Prelims 2009)
34. Trichoderma harzianum has proved a useful microorganism for
(a) gene transfer in higher plants
(b) biological control of soil-borne plant pathogens
(c) bioremediation of contaminated soils
(d) reclamation of wastelands. (Prelims 2008)
35. Nitrogen fixation in root nodules of Alnus is brought about by
(a) Frankia
(b) Azorhizobium
(c) Bradyrhizobium
(d) Clostridium. (Prelims 2008)
36. Which one of the following proved effective for biological control of nematodal diseases in plants?
(a) Gliocladium virens
(b) Paecilomyces lilacinus
(c) Pisolithus tinctorius
(d) Pseudomonas cepacia. (Prelims 2008)
37. Probiotics are
(a) cancer inducing microbes
(b) new kind of food allergens
(c) live microbial food supplement
(d) safe antibiotics. (2007)
38. Which one of the following pairs is wrongly matched?
(a) Yeast – Ethanol
(b) Streptomycetes – Antibiotic
(c) Coliforms – Vinegar
(d) Methanogens – Gobar gas. (2007)
39. Dough kept overnight in warm weather becomes soft and spongy because of
(a) absorption of carbon dioxide from atmosphere
(b) fermentation
(c) cohesion
(d) osmosis. (2004)
40. Which one of the following pairs is not correctly matched?
(a) Streptomyces – Antibiotic
(b) Serratia – Drug addiction
(c) Spirulina – Single cell protein
(d) Rhizobium – Biofertilizer. (2004)
41. The most thoroughly studied of the known bacteria- plant interactions is the
(a) cyanobacterial symbiosis with some aquatic ferns
(b) gall formation on certain angiosperms by Agrobacterium
(c) nodulation of Sesbania stems by nitrogen fixing bacteria
(d) plant growth stimulation by phosphate- solubilising bacteria. (2004)
42. A major component of gober gas is
(a) ammonia
(b) methane
(c) ethane
(d) butane. (2004)
43. During anaerobic digestion of organic waste, such as in producing biogas, which one of the following is left undegraded ?
(a) lipids
(b) lignin
(c) hemi-cellulose
(d) cellulose (2003)
44. Which bacteria is utilized in gober gas plant?
(a) methanogens
(b) nitrifying bacteria
(c) ammonifying bacteria
(d) denitrifying bacteria. (2002)
45. During the formation of bread it becomes porous due to release of C02 by the action of
(a) yeast
(b) bacteria
(c) virus
(d) protozoans. (2002)
46. Which of the following is the pair of biofertilizers
(a) Azolla and BGA
(b) Nostoc and legume
(c) Rhizobium and grasses
(d) Salmonella and E.coli. (2001)
47. Spoilage of oil can be detected by which fatty acid
(a) oleic acid
(b) linolenic acid
(c) linoleic acid
(d) erucic acid. (2001)
48. Which aquatic fem is used to increase the yield in paddy crop?
(a) Azolla
(b) Salvinia
(c) Marsilea
(d) Isoetes. (2000)
49. Which of the following is used to manufacture ethanol from starch?
(a) Penicillin
(b) Saccharomyces
(c) Azotobactor
(d) Lactobacillus. (2000)
50. Which of the following fern is an excellent biofertilizer?
(a) Marsilia
(b) Pteridium
(c) Azolla
(d) Salvinia. (1999)
51. Which of the following is non-symbiotic biofertilizer?
(a) Anabaena
(b) Rhizobium
(c) VAM
(d) Azotobacter. (1998)
52. Yeast (Saccharomyces cerevisiae) is used in the industrial production of
(a) tetracyline
(b) ethanol
(c) butanol
(d) citric acid. (1998)
53. Farmers have reported over 50% higher yields of rice by using which of the following biofertilizer?
(a) Cyanobacteria
(b) legume-Rhizobium symbiosis
(c) Mycorrhiza
(d) Azollapinnata. (1998)
54. Which of the following microorganisms is used for production of citric acid in industries?
(a) Aspergillus niger
(b) Rhizopus nigricans
(c) Lactobacillus bulgaris
(d) Penicillium citrinum. (1998)
55. Biological control component is central to advanced agricultural production. Which of the following is used as a third generation pesticide?
(a) insect repellants
(b) organophosphate and carbamates
(c) pathogens
(d) pheromones. (1998)
56. The biofertilizers are
(a) Anabaena and Azolla
(b) cow dung, manure and faryard waste
(c) quick growing crop ploughed under soil
(d) none of these. (1997)
57. Gobar gas contains mainly
(a) CO2 + H2
(b) CO2 + H2O
(c) CH4 only
(d) CH4 + CO2. (1997)
58. Cochineal insects have proved very useful for
(a) Cactus prevention
(b) Eicchornia prevention
(c) weeds control
(d) Parthenium contol. (1996)
59. When a natural predator (living being) is applied
on the other pathogen organism to control them, this process is called
(a) artificial control
(b) confusion technique
(c) biological control
(d) genetic engineering. (1996)
60. The citric acid is produced by
(a) Candida utilis
(b) Azotobacter suboxydans
(c) Aspergillus niger
(d) Streptococcus lactis. (1995)
61. The rotenone is
(a) a natural herbicide
(b) a natural insecticide
(c) an insect hormone
(d) a bioherbicide. (1995)
62. The organism used for alcohol fermentation, is
(a) Aspergillus
(b) Saccharomyces
(c) Pseudomonas
(d) Penicillium. (1995)
63. One of the maj or difficulties in the biological control of insect pest is that
(a) the method is less effective as compared with the use of insecticides
(b) the practical difficulty of introducing the predator to specific areas
(c) the predator develops a preference to other diets and may itself become a pest
(d) the predator does not always survive when transferred to a new environment. (1995)
64. Biological control of agricultural pests, unlike chemical control, is
(a) self perpetuating
(b) polluting
(c) very expensive
(d) toxic. (1994)
65. In cheese manufacture, the microorganisms are important for
(a) the ripening only
(b) the souring of milk only
(c) the development of resistance to spoilage only
(d) both the souring and the ripening processes. (1994)
66. Which of the following species does not have the ability to fix atmospheric nitrogen?
(a) Azotobactor
(b) Anabaena
(c) Nostoc
(d) Spirogyra. (1994)
67. Which one of the following statements is correct?
(a) legumes fix nitrogen only through the specialized bacteria that live in their roots
(b) legumes fix nitrogen independently of the specialized bacteria that live in their roots
(c) legumes fix nitrogen only through specialized bacteria that live in their leaves
(d) legumes are incapable of fixing nitrogen. (1994)
Explanations
1. (c)
2. (a) :
Methanogens like Methanobacterium are found in the rumen (a part of the stomach) of cattle. A lot of cellulosic material is also available in the rumen. In rumen, these bacteria help in the breakdown of cellulose and play an important role in nutrition of cattle.
3. (b) :
Amanita muscaria is a member of class Basidiomycetes. It is a poisonous mushroom and has hallucinogenic properties. It produces a toxic alkaloid, muscarine, which mimics the effects of acetylcholine and binds to muscarinic receptors as well as ibotenic acid which also binds to different receptors. This leads to excitation of neurons bearing these receptors and hence hallucinations.
4. (b):
Chlorella is a single celled chlorophycean alga with rich protein content. It is considered as a source of SCP (single cell protein) and also as food source during long space travels.
5. (b):
The type of gases produced by microbial activity depend upon the microbes and the organic substrates they utilise. Certain bacteria, called methanogens, grow anaerobically on cellulosic material and produce large amount of methane along with carbon dioxide. These bacteria are commonly found in the anaerobic sludge during sewage treatment. Other anaerobic bacteria, involved in the process of anaerobic digestion produce other gases like ammonia and hydrogen sulfide.
6. (c) :
Aspergillus niger produces citric acid, Clostridium butylicum produces butyric acid, Saccharomyces is used for commercial production of ethanol, Pseudomonas produces alkaline proteases.
7. (b) :
Biopesticides are those biological agents that are used for control of weeds, insects and pathogens. The microorganisms used as biopesticides are viruses, bacteria, protozoa, fungi and mites. Some of the biopesticides are being used at a commercial scale. Most important example is the soil bacterium, Bacillus thuringiensis (Bt). Spores of this bacterium produce the insecticidal cry protein. Therefore, spores of this bacterium kill larvae of insects which eat them.
8. (d) :
Statins are produced by the yeast Monascus purpureus which have been commercialized as blood- cholesterol lowering agents. It acts by competitively inhibiting the enzyme responsible for synthesis of cholesterol.
9. (b) :
Streptokinase (Tissue Plasminogen Activator or TPA) is an enzyme obtained from the culture of some haemolytic bacterium Streptococcus which is modified genetically to function as clot buster. Therefore, it helps in clearing blood clots inside the blood vessels through dissolution of intravascular fibrin during myocardial infarction.
10. (b) :
Azolla plays a very important role in rice production. Azolla and its nitrogen-fixing partner, Anabaena, have been used as green manure to fertilize rice paddies and increase production. With the help of Azolla, rice can be grown year after year, several crops a year, with little or no decline in productivity; hence no rotation of crops is necessary.
11. (a):
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.
12. (b):
Biogas or gobar gas is a methane rich fuel gas produced by anaerobic breakdown or digestion of biomass with the help of methanogenic bacteria. It is made up of methane (50 – 70%), carbon dioxide (30 – 40%) with traces of nitrogen, hydrogen sulphide and hydrogen.
13. (b):
Chikungunya is caused by Chikungunya vims. Colostrum is the first breast milk of mother which contains antibodies (especially IgA) which protect the infant by the age of three months. Beer is manufactured by fermentation of barley malt by yeast species.
Tissue culture can be used to obtain virfts-free healthy plants from diseased plants. Although the plant is infected with vims, the meristem (apical and axillary) is free of vims. This is because cells of meristematic region are actively dividing cells and vims cannot keep pace with these cells. Consequently their number is much low in meristematic region and sometimes they are completely absent here. Hence, meristem can be removed and grown in vitro to obtain virus-free plants.
14. (b):
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 floes. Floes 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, H2S and CO2.
15. (d)
16. (d):
The many and varied raw materials used in the manufacture of ethanol are classified into three types. These are sugar, starch and cellulose materials. Sugars (from sugarcane, sugar beets, molasses, fruits) can be converted to ethanol directly. Starch obtained from grains, potatoes, root crops is first hydrolyzed to fermentable sugars by the action of enzymes from malt or maids. Cellulose are also first converted to sugars by mineral acids. Once simple sugars are formed, enzymes from yeast readily ferments it into ethanol.
17. (a):
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 an 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.
18. (d):
Secondary sewage treatment is mainly a biological process. In secondary treatment primary effluent is passed into large aeration tanks, where it is constantly agitated mechanically and air is pumped into it. This allows vigorous growth of useful aerobic microbes into floes. Floes is the masses of bacteria associated with fungal filaments to form mesh like structures. These microbes consume the major part of the organic matter in the effluent while growing. This significantly reduces the BOD (Biological Oxygen Demand) of the effluent. After the reduction of BOD, effluent is passed in a setting tank called activated sludge, where bacterial floes are allowed to sediment. This sludge is large tank, where bacteria and the fungi are digested by an aerobic bacteria present in the large tank called, anaerobic sludge digester and produce biogas.
19. (d):
Marsh gas or methane gas is mainly produced by the activities of anaerobic bacteria on sewage. Sewage contains large amounts of organic matter and microbes, many of which are pathogenic. These microbes (bacteria and fungi) are digested during secondary treatment process of sewage by anaerobic bacteria. During digestion, bacteria produce a mixture of gases such as methane, hydrogen sulphide and carbon dioxide. These gases are called biogas and can be easily used as a source of energy as it is inflammable.
20. (c) :
Rhizobium is used as a biofertilizer for raising crop. Rhizobium japonicum forms symbiotic association
in the roots of the leguminous plant, soyabean.
21. (a):
Ethanol is commercially produced through a particular species of yeast Saccharomyces (Saccharomyces cerevisiae).
22. (b)
23. (b):
Methanogens are any of various archaebacteria that produce methane; they include genera such as Methanobacillus and Methanothrix. Methanogens are obligate anaerobes found in oxygen-deficien environments, such as marshes, swamps, sludge and the digestive systems of ruminants.
24. (b):
Cyclosporin A used as an immunosuppressive agent in organ-transplant patients, is produced by the fungus Trichoderma polysporum.
25. (c) :
Organic farming is the form of agriculture that relies on techniques such as crop rotation, green manure, compost and biological pest control to maintain soil productivity and control pest on a farm. Organic farming excludes or strictly limited the use of manufactured fertilizers, pesticides (which include herbicides, insecticides and fungicides), plant growth regulators such as hormones, food additives and genetically modified ori
26. (c) :
Microbes are used for commercial and industrial production of certain chemicals like organic acids, alcohols and enzymes. Examples of acid producers axe Aspergillus nigex (a fungus) of citric acid, Acetobacter aceti (a bacterium) of acetic acid; Clostridium butylicum (a bacterium) ofbutyric acid and Lactobacillus (a bacterium) of lactic acid.
27. (d):
In activated sludge system (secondary sewage treatment), the primary effluent is taken to aeration tank. A large number of aerobic heterotrophic microbes grow in aeration tank. They form floes, which digest a lot of organic matter. As the BOD of waste water is reduced sufficiently, it is passed into setting tank where bacterial floes are allowed to undergo sedimentation. The sediment of the settling tank is called activated sludge which is a rich source of aerobic bacteria. It is further processed in anaerobic sludge digester. Biogas commonly called gobar gas is produced by anaerobic breakdown of biomass with the help of methanogenic bacteria. Biogas is made up of methane (50-70%), CO2 (30-40%) with traces ofnitrogen, hydrogen sulphide and hydrogen. Methanobacterium is an anaerobic methanogenic bacteria which is found in rumen of cattle and helpful in the breakdown of cellulose.
28. (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 ofplant diseases. Baculoviruses (mostly of genus Nucleo-polyhedrovirus) 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.
29. (b):
Azospirillum is an anaerobic nitrogen fixing bacteria which forms loose association with roots of some plants. Inoculation of paddy fields with these bacteria helps in increasing yield and saving of nitrogen fertilizers.
30. (d):
Organic farming is a method of farming system which primarily aimed to keep the soil alive and in good health by use of organic wastes and other biological material alongwith beneficial microbes (biofertilizers) to release nutrients to crops for increased sustainable production in an ecofriendly, pollution free environment. Basic components of organic farming are green manures, farm yard manure, vermicompost, crop rotation, biopesticides and biofertilizers. Glomus being a myeorrhizal component, earthworm being a vermicompost and Oscillatoria being a nitrogen fixing blue green algae can be used in organic farming. Snail cannot be a component of organic farming.
31. (b) :
The genus Glomus form endomycorrhiza, a symbiotic associations with plants. The fungal symbiont in these associations absorbs phosphoms from soil and passes it to the plant. Plants having such associations show other benefits also, such as resistance to root-borne pathogens, tolerance to salinity and drought, and an overall increase in plant growth and development.
Nostoc is a blue green algae, Agaricus is a basidiomycetes, Rhizobium is a eubacteria.
32. (a) :
Yeast species are used in alcoholic fermentation due to the presence of zymase enzyme. It was known that the yeast extract contained an enzyme zymase, which is nondialyzable and a coenzyme which is dialyzable. It is now well known that the zymase is a complex mixture of many enzymes and that several coezymes are necessary for their function. The activity of this enzyme was lost because the main enzyme was separated from its coezyme during dialyzation. Thus, it was established later that extracellular enzyme zymase,secreted by yeast cells, carry out the process of fermentation.
33. (c):
Nucleopolyhedrosis vims (NPV) is used to kill asiatic rice borer,cotton leaf worm,cabbage looper etc. Trichoderma is used to kill fungal plant pathogen of groundnut, chick pea etc. Bacillus thuringiensis produces protoxin crystal protein which is used to kill lepidopteran and dipteran larvae.
34. (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.
35. (a):
The most common symbiotic association of legume and bacteria on roots is as nodules, which are small outgrowth on the roots. The microbe Frankia is symbiont in root nodules of several non-legume plants like Casurina and Alnus. Both Rhizobium and Frankia are free living in soil but as symbiont can fix atmospheric nitrogen.
36. (b) :
Paecilomyces lilacinus proved effective for biological control of nematodal diseases in plant.
37. (c) :
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. This not only provides the characteristic sour taste of fermented dairy foods such as yogurt, but acts as a preservative, by lowering the pH and creating fewer opportunities for spoilage organisms to grow. Probiotic bacterial cultures are intended to assist the body’s naturally occurring gut flora to re¬establish themselves. Experiments into the benefits of probiotic therapies suggest a range of potentially beneficial medicinal uses for probiotics, like
- Managing lactose intolerance
- Prevention of colon cancer
- Cholesterol lowering
- Lowering blood pressure
- Improving immune function and preventing infections
- Reducing inflammation
- Improving mineral absorption
- Prevents harmful bacterial growth under stress
- Irritable bowel syndrome and colitis
38. (c):
Coliform bacteria are a commonlyused bacterial indicator of sanitary quality of foods and water. It is not involved in the production of vinegar.
39. (b)
40. (b) :
Serratia marcescens is considered a harmful human pathogen which has been known to cause urinary tract infections, wound infections, and pneumonia. Serratia bacteria also have many antibiotic resistance properties which may become important if the incidence of Serratia infections dramatically increases.
41. (b) :
Agrobacterium tumefaciens is the causative agent of crown gall, an important disease of many commercial crops. This disease has come to be recognized in recent years as being caused by a DNA plasmid (Ti plasmid) carried by bacterium and transferred to the plant cells.
Following the discovery of the relationship between crown gall and the Ti plasmid, this plasmid has come to be widely used in plant genetic engineering as a vector, novel plant genes being spliced into the plasmid sequence by gene manupulation and thus carried into the host plant cells. This offers the possibility of recombination between the novel sequence in the plasmid and the plant geniomic DNA. Successful recombination would result in integration of the novel sequence into the plant cell genome and expression of the sequence in the life of the cell. Since many plants can be grown from single somatic cells into complete plants, this system provides the opportunity to develop new and better plant species. Some such success has already been achieved.
42. (b):
Refer answer 12.
43. (b):
Lignin is a complex polymer of phenylpropane units, which are cross-linked to each other with a variety of different chemical bonds. This complexity has thus far proven as resistant to microbial degradation.
Cellulose is a long chain of glucose molecules, linked to one another primarily with glycosidic bonds. The simplicity of the cellulosic structure, using repeated identical bonds, means that only a small number of enzymes are required to degrade this material. Hemicelluloses are branched polymers of xylose, arabinose, galactose, mannose, and glucose. Hemicelluloses bind bundles of cellulose fibrils to form microfibrils, which enhance the stability of the cell wall but these can be degraded by increasing the number of enzymes.
44. (a):
Methanogens are a type of archaebacteria that occurs in marshes, swamps and rumen of cattles. They are obligate anaerobes that can catabolize acetate and H2 to gaseous products and are used in the final stage called methanogenesis of biogas production in gobar gas plant. Nitrifying bacteria oxidise NH3 into NO2 and later to NO3 Ammonifying bacteria convert proteins into NH3. Denitrifying bacteria reduce NO3into NH3.
45. (a) :
Saccharomyces converts starch or sugars to pyruvic acid through EMP pathway. Then this pyruvic acid is converted to acetaldehyde and finally to ethyl alcohol in the absence of oxygen. This entire process is called fermentation.
C6H12O6 -> 2CH2COCOOH -> 2C2H5OH + 2CO2
This released carbon dioxide from yeast makes the dough to rise and gives spongy nature to bread.
46. (a):
Refer answer 10.
47. (d):
Erucic acid is an unsaturated fatty acid belonging to the oleic acid series, occurring as glycerides in rape seed oil and other vegetable oils. It is the cis-isomer, the trans-isomer being brassidic acid. Erucic acid is used as a binder for oil paints. Its high tolerance to temperature makes it suitable for trans mission oil. It is useful in manufacture of emulsions to coat photographic films and papers. Oleic acid is found in various animal and vegetable sources. It is widely used in industries including textile, chemical, medicine, leather, stationary, paper making etc. Linolenic acids is used in making soaps, emulsifiers and quick-drying oils, in beauty products. It helps in acne reduction, moisture retention etc.
Linoleic aicd is an important fatty acid especially for growth and development of infants. Commercially it is used in margarine, animal feeds, soaps and drugs.
48. (a) :
Refer answer 10.
49. (b) :
Saccharomyces convert starch or sugars to pyruvic acid through EMP pathway. Then this pyruvic acid is converted to acetaldehyde and finally to ethyl alcohol in the absence of oxygen. This entire process is called fermentation.
C6H12O6 -> 2CH2COCOOH -> 2C2H5OH + 2CO2
50. (c) :
Azolla is a fern in the leaf cavities of which the blue green algae Anabaena is found. This Azolla-Anabena symbiotic system is the main biofertilizer which increases yield upto 50% Anabaena fixes nitrogen which is excreted in foe leaf cavities and is made available to the fern. When the fem plants die and decay they release nitrogen for utilization of the rice plants.
51. (d):
Biofertilizers are organisms which bring about nutrient enrichment of the soil. Azotobacter is a free living, aerobic, nitrogen fixing bacteria. Anabena is a nitrogen fixing cyanobacteria that occurs in both free living and symbiote associations with Azolla, Cycas roots etc. Rhizobium lives symbiotically in root nodules of legumes and non-legumes. Vesicular-arbuscular mycorrhiza (VAM) is an example of endomycorrhiza in which fungal hyphae penetrate the cortical cells of grasses to form vesicles.
52. (b) :
Refer answer 49.
53. (d):
Refer answer 10.
54. (a) :
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.
55. (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.
56. (a) :
Refer answer 51.
57. (d) :
Refer answer 12.
58. (a):
Extensive growth of Opuntia (Cactus) in Australia was checked through introduction of its natural herbivore, cochineal insect (Cactoblastis cactorum).
59. (c):
The control of insect pests by the introduction, encouragment and artificial increase ofbiological 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.
60. (c):
Citric acid is produced by aerobic fermentation of sucrose in beet molasses by Aspergillus niger. The fermentation process is completed in about 5 – 14 days at 27 – 33°C. Citric acid is made available in the market in the form of anhydrous crystalline chemical as powder. Citric acid is used in food industry (e.g. fruit drinks, confectionery, jams, jellies, preserved fruits), pharmacy (e.g. blood transfusion), consmetics (e.g. astringent lotions, shampoos and hair setting fluids), and industries (e.g. electroplating leather tanning).
61. (b):
Natural insecticides are those which are obtained from microorganisms and plants. The first natural insecticide used by man is azadirachtin obtained from Azadirachta indica.
Rotenone is another natural insecticide which is obtained from the roots ofDerris and Lonchocarpers. It is harmless to warm blooded animals.
62. (b) :
Refer answer 49.
63. (d) :
The control of insect pests by the introduction, encouragment and artificial increase ofbiological agencies like predaceous and parasitic insects, other animals and diseases is termed as bilological 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. It is just possible that predators of a particular plant pest are unable to get established and multiply in a particular environment. In such cases, the predators are reared in the laboratory and let off at a particular time when the pests are about to threaten the crops. And then this practice become expensive.
64. (a):
Refer answer 59.
65. (d) :
Cheese is a protein rich nutritive preparation obtained after fermentation and curding of milk. Cheese contains proteins (20-35%), fats (20-30%), minerals, vitamins and water. Milk is first curdled (soured) with the help of a lactic acid bacterium. Curd is gently heated to separate cheese from liquid called whey. Curd is placed in cloth-lined porous containers for draining out whey. The left out solidified material is called cottage cheese. For preservation and ripening, blocks of cottage cheese are salted and placed in brine solution. Salt solution is drained out. Cheese blocks are wiped and placed in sterilised rooms for ripening with the help of micro¬organisms.
66. (d) :
Members of kingdom monera – bacteria and cyanobacteria (blue green algae) have the ability to fix nitrogen. Azotobacter is a N2-fixing bacteria. Anabaena and Nostoc are heterocystous blue-green algae. The heterocysts are the sites of N2-fixation. Spirogyra is one of the commonest green algae. It has no function in nitrogen fixation.
67. (a):
The nitrogen-fixing ability of leguminous plants is not a property of the plants as such but results from infection of their roots by bacteria in the soil, infection leading to the formation of nodules. These organisms are Gram-negative motile rods that are classified in the genus Rhizobium.
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