10

Q1. Rotenone is a

• 1) Bioherbicide
• 2) Natural herbicide
• 3) Insect hormone
• 4) Natural insecticide

Solution

Rotenone is obtained from the roots of Derris elliptica. It has insecticidal properties and is used as a natural insecticide.

Q2. Bacillus thuringiensis (Bt) strains have been used for designing novel

• 1) Bio-fertilisers
• 2) Bio-metallurgical techniques
• 3) Bio-mineralisation processes
• 4) Bio-insecticidal plants

Solution

The bacterium Bacillus thuringiensis (Bt) strains contains genes for insecticidal crystal proteins. These have been isolated from the bacteria and incorporated into the genetic material of various crop plants through recombinant DNA technology. Bt-cotton is one such example of bio-insecticidal plant.

Q3. Which of the following is a product of yeast fermentation?

• 1) Caproic acid
• 2) All of the above
• 3) Lactic acid
• 4) n-Propanol

Solution

Some of the products obtained from yeast fermentation are ethanol, caproic acid, lactic acid, n-propanol, glycerol, butanol and acetaldehyde.

Q4. Alexander Fleming is associated with 

• 1) Anthrax
• 2) Ethanol production
• 3) Yeast fermentation
• 4) Penicillin

Solution

Alexander Fleming discovered the antibiotic penicillin and explored its possible therapeutic use.

Q5. Milk begins to coagulate when lactic acid bacteria (LAB) are added to warm milk as a starter. Mention any other two benefits that LAB provide.

Solution

Other benefits of LAB: (i) Increase the nutritional quality of curd by increasing vitamin B₁₂ content (ii) Inhibit the growth of disease-causing microbes in the gut

Q6. The major component of biogas is

• 1) Oxygen
• 2) Methane
• 3) Hydrogen
• 4) Nitrogen

Solution

Methane is the major component of biogas, consisting of about 50-68% of the total gas.

Q7. Which one of the following microbes is used in the commercial production of ethanol?

• 1) Clostridium butyricum
• 2) Saccharomyces cerevisiae
• 3) Trichoderma polysporum
• 4) Streptococcus spp.

Solution

The yeast Saccharomyces cerevisiae is used in the brewing industry for the preparation of alcoholic drinks like ethanol, beer, wine etc. through fermentation. Certain Streptococcus species produce lactic acid. Trichoderma polysporum is being developed as an effective biocontrol agent of several plant pathogens.  Clostridium butyricum is a bacterium used for the production of butyric acid.

Q8. Formation of compost requires how many months?

• 1) 2-4 months
• 2) 6-8 months
• 3) 10-12 months
• 4) 1-3 months

Solution

Compost is formed by the degradation of organic wastes such as dung, farm waste and crop residue. The preparation of compost from organic matter takes about 6-8 months.

Q9. Which bacterium is used in the production of Swiss cheese?

• 1) Streptococcus faecalis
• 2) Penicillium roqueforti
• 3) Pedicoccus cerevisiae
• 4) Propionibacterium sharmanii

Solution

Propionibacterium sharmanii is used in the production of Swiss cheese. The bacterium gives the cheese its characteristic flavour and is responsible for the large holes in the cheese body. 

Q10. Which of the following is a non-symbiotic biofertiliser?

• 1) Rhizobium
• 2) Vesicular arbuscular mycorrhizae
• 3) Azotobacter
• 4) Anabaena

Solution

Azotobacter is a free-living, non-symbiotic nitrogen-fixing bacterium found in the soil. It fixes atmospheric nitrogen and makes it available to plants.

Q11. VAM contains

• 1) Saprophytic bacteria
• 2) Saprophytic fungi
• 3) Symbiotic fungi
• 4) Symbiotic bacteria

Solution

Vesicular Arbuscular Mycorrhiza (VAM) is an important mycorrhizal association. In this association, the fungal mycelium forms some special kinds of organs called vesicles and arbuscules within the root cortical cells. The vesicles and arbuscules serve as the food storage organs of the fungus.

Q12. Which of the following is not degraded during anaerobic digestion of organic waste?

• 1) Cellulose
• 2) Lipid
• 3) Lignin
• 4) Hemicellulose

Solution

Lignin is a complex plant polymeric molecule which remains undigested by anaerobic bacteria during the decomposition of organic waste.

Q13. Toddy is prepared by the fermentation of

• 1) Latex of toddy palm
• 2) Dried fish
• 3) Coconut water
• 4) Both latex of toddy palm and coconut water

Solution

Toddy is prepared by the fermentation of the latex of toddy palm and coconut water.

Q14. A sewage treatment process in which a part of the decomposer bacteria present in the wastes are recycled into the starting of the process is called

• 1) Tertiary treatment
• 2) Cyclic treatment
• 3) Primary treatment
• 4) Activated sludge treatment

Solution

Activated sludge refers to a mass of microorganisms cultivated in the sewage treatment process to break down organic matter into carbon dioxide, water and other inorganic compounds. The activated sludge treatment process has three basic components- a reactor in which the microorganisms are kept in suspension, aerated and in contact with the waste they are treating, liquid-solid separation and a sludge recycling system for returning activated sludge back to the beginning of the process.

Q15. Expand LAB.

• 1) Latent antibiotic bacteria
• 2) Lactic acid biogenesis
• 3) Lactic acid bacteria
• 4) Latent antibiotic biogenesis

Solution

LAB stands for lactic acid bacteria, which are used in various fermentation processes.

Q16. Which of the following gases is not produced in a biogas plant?

• 1) Oxygen
• 2) Methane
• 3) Hydrogen
• 4) Sulphur

Solution

The major gas produced in a biogas plant is methane, which accounts for about 50-68% of the total gases produced. The other gases produced include hydrogen, carbon dioxide, nitrogen, oxygen and, in some cases, hydrogen sulphide.

Q17. An example of endomycorrhiza is

• 1) Glomus
• 2) Agaricus
• 3) Nostoc
• 4) Rhizobium

Solution

Glomus is a genus of arbuscular mycorrhizal (AM) fungi which is used as a biofertiliser. Nostoc is a cyanobacterial biofertliser. Agaricus is a genus of mushrooms. Rhizobium forms an endosymbiotic nitrogen fixing association with roots of legumes and Parasponia.

Q18. A good example of organic fertilizer which improves phosphorus uptake is

• 1) None of these
• 2) Streptomyces
• 3) Saccharomyces
• 4) Azospirillum

Solution

Microphos biofertlisers include microorganisms such as Azospirillum, Pseudomonas and Bacillus, which solubilise bound phosphate of rocks and soil to increase the availability of soluble phosphate to the plants. The phosphate dissolving bacteria reduce the pH of the substrate by secretion of a number of organic acids. This causes release of soluble inorganic phosphate into the soil through decomposition of phosphate-rich organic compounds.

Q19. Which cheese is characterised by large holes?

• 1) Cottage cheese
• 2) Goat cheese
• 3) Roquefort cheese
• 4) Swiss cheese

Solution

Swiss cheese is known for its characteristic flavour and large holes. These holes are formed due to the production of a large amount of CO_2­ during the fermentation process.

Q20. Explain in brief about the Yamuna Action Plan.

Solution

Most of the sewage water from urban as well as rural areas was discharged directly into the rivers resulting in their pollution. In order to protect the major rivers in India from sewage pollution, the Ministry of Environment and Forests has initiated development of sewage treatment plants under the National River Conservation Authority, e.g. Ganga Action Plan, Yamuna Action Plan etc. Under these plans, a large number of sewage treatment plants were built so that only treated sewage is discharged in the rivers. Importance of microbial treatment of sewage was then realized and more sewage treatment plants were established.

Q21. Nematicides are components used to protect plants against

• 1) Mice
• 2) Ticks
• 3) Nematodes
• 4) Mites

Solution

Nematicides are components used to protect plants against nematodes.

Q22. What are the advantages of using biofertilisers in agriculture?

Solution

Advantages of using biofertilisers in agriculture: 1. They do not cause any form of environmental pollution. 2. They are inexpensive and economical. 3. At places where irrigation is not sufficient, few biofertilisers even improve the crop yield. 4. They enhance soil structure and function. 5. They increase the availability of vitamins and other growth promoting substances.

Q23. Why is Rhizobium categorised as a 'symbiotic bacterium'? How does it act as a biofertiliser?

Solution

Rhizobium forms a symbiotic association with the root nodules of leguminous plants. The bacterium obtains food and shelter from the plant and the plant in turn, gets the fixed nitrogen. It multiplies as soon as it gets the rhizosphere of leguminous plants, enters inside their roots and forms root nodules. These bacteria fix atmospheric nitrogen into organic forms, which is used by the plant as a nutrient.

Q24. What are biofertilisers? Give the significance of biofertilisers.

Solution

Biofertilisers are organisms that enrich the nutrient quality of soil. Significance of biofertilisers: 1. Increase the soil fertility 2. Reduce the use of chemical fertilisers and in turn, the chances of environmental pollution

Q25. The term antibiotic was first used by

• 1) Lister
• 2) Flemming
• 3) Pasteur
• 4) Waksman

Solution

Antibiotics are chemical compounds produced by microorganisms that inhibit or slow down the growth of bacteria. The term antibiotic was first used by Selman Waksman and his collaborators in 1942 in journal articles to describe any substance produced by a microorganism that is antagonistic to the growth of other microorganisms in high dilution.

Q26. (a) What are biopesticides? Give any two examples of their application. (b) What are mycorrhizae? How do they act as biofertilisers?

Solution

(a) Biopesticides are biological control agents and their products are used to control pests like weeds, insects and pathogens. Bioherbicides like Dalpon are used to control broad-leaved weeds of cereal crops and Baculoviruses are bioinsecticidal viral pathogens that kill insects and other arthropods. (b) The symbiotic association of fungi and roots of higher plants is called mycorrhiza. The fungal hyphae increase the absorptive surface of roots which facilitates better intake of nutrients such as nitrogen, phosphorus, calcium etc., assist in absorption of water, carry out solubilisation of complex organic molecules into simple inorganic nutrients, their absorption and transfer to roots, offer protection to the plants from the attack of disease-causing pathogens by secreting antimicrobial substances and provide tolerance to salinity and drought.  

Q27. The bacterium responsible for curd formation is

• 1) Leuconostoc mesenteroides
• 2) Streptococcus thermophilus
• 3) Pedicoccus cerevisiae
• 4) Saccharomyces cerevisiae

Solution

The two most commonly used bacteria which help convert milk to curd are Lactobacillus bulgaricus and Streptococcus thermophilus.

Q28. The aquatic fern which is an excellent example of a biofertiliser is

• 1) Pteridium
• 2) Marsilea
• 3) Azolla
• 4) Salvinia

Solution

Leaves of Azolla carry colonies of Anabaena, which help fix nitrogen and make it available to plants. Hence, Azolla is used as a biofertiliser to supply nitrogen to plants.

Q29. List the characteristics of an ideal pesticide.

Solution

An ideal pesticide should possess the following characteristics: 1. It should be inexpensive and easily available. 2. It should be effective only against the specific target organism. 3. It should be non-persistent. 4. It should be non-toxic to other living organisms. 5. It should be biodegradable.

Q30.     The above diagram shows a typical biogas plant. Explain the sequence of events occurring in a biogas plant. Identify a, b and c.

Solution

The biogas plant tank is fed with a mixture of dung or waste materials from kitchen and night soil along with water. The biogas tank is covered with a floating lid which keeps on rising as the gas is produced in the slurry due to the microbial activity of methanogens like Methanobacterium. Methanogens grow anaerobically on cellulosic material in cowdung to produce a large amount of methane, CO₂ and H₂. The biogas plant has an outlet, which is connected to a pipe to supply biogas. The leftover slurry is removed through another outlet and is used as fertiliser. a: Sludge tank b: Gas holder c: Charge pit

Q31. (a) Baculoviruses are excellent candidates for integrated pest management in an ecologically sensitive area. Explain giving two reasons. (b) What is organic farming? Why is it suggested to switch over to organic farming?

Solution

(a) Baculoviruses are excellent candidates for integrated pest management in an ecologically sensitive area because: (i) Baculoviruses are biological control agents. They are an excellent source for species-specific, narrow-spectrum insecticidal applications. (ii) They have no negative effect on plants, mammals or even on non-target insects.   (b) The use of biofertilisers and biopesticides to improve crop yields to minimise the problems associated with the overuse of chemical fertilisers is known as organic farming. It is advisable to switch to organic farming due to the following reasons: (i) Excessive use of chemical fertilisers makes the soil unfit for cultivation. (ii) Natural resources get depleted due to the production of chemical fertilisers.

Q32. How is the presence of cyanobacteria in paddy fields beneficial to the rice crop?

Solution

Cyanobacteria can fix atmospheric nitrogen. The soil conditions in paddy fields provide suitable environment for the growth of nitrogen fixing cyanobacteria. Cyanobacteria act as important biofertilisers. They also add organic matter to the soil and increase its fertility.

Q33. Fill in the blank spaces a, b, c and d in the table given below:   Type of microbe Name Commercial product Fungus a Penicillin Bacterium Acetobacter aceti b c Aspergillus niger Citric acid Yeast d Ethanol    

Solution

(a) Penicillium notatum (b) Acetic acid (c) Fungus   (d) Saccharomyces cerevisiae

Q34. Describe a biogas plant in brief.

Solution

Biogas is a mixture of gases produced from decomposable organic matter by the activity of various anaerobic bacteria that can be used as a fuel.       Mechanism of biogas production: 1. The biogas plant tank is fed with a mixture of dung or waste materials from kitchen and night soil along with water. 2. The biogas tank is covered with a floating lid which keeps on rising as the gas is produced in the slurry due to the microbial activity of methanogens like Methanobacterium. 3. Methanogens grow anaerobically on cellulosic material in cowdung to produce a large amount of methane, CO₂ and H₂. 4. The biogas plant has an outlet, which is connected to a pipe to supply biogas. The leftover slurry is removed through another outlet and is used as fertiliser. 5. Biogas is used as a fuel for heating and cooking, lighting, power for irrigation and other purposes as an alternative for firewood, kerosene, electricity and LPG. It is considered as an ecofriendly and pollution free source of energy.