NEET Biology Microbes in Human Welfare Important Questions Set 02

These Class 12 NEET Biology important questions on Microbes in Human Welfare give 21 questions with step-by-step answers, arranged as very short, short and long answer types, taken from a model test paper. They help NEET aspirants revise the definitions, structures, differences and key terms of the chapter.

Very Short Answer Type Questions

Question 1. Name an odd place where no other organisms except some microbes can survive.
Answer: The odd place where no other organism except some microbes can survive can be deep inside geysers [thermal vents] where the temperature may be as high as 100ºC.

Question 2. Expand LAB.
Answer: LAB stand for Lactic acid bacteria.

Question 3. Give two examples where microbes are used in industrial scale production.
Answer: Microbes are used in the industrial scale production of beverages and antibiotics.

Question 4. Define BOD.
Answer: BOD [Biochemical oxygen demand] is the amount of oxygen that would be consumed if all the organic matter in one liter of water were oxidised by bacteria.

Question 5. How Ladybird and Dragonfly are used as biocontrol agents?
Answer: Ladybird and Dragonflies are useful to get rid of aphids and mosquitoes respectively.

Question 6. Name two free living bacteria used as biofertilisers.
Answer: Two free living bacteria used as biofertiliser are Azospirillum and Azotobacter.

Short Answer Type Questions

Question 7. How curd is nutritionally more beneficial than milk? What is the beneficial role of LAB in our stomach?
Answer: When milk is converted into curd, its nutritional quality is improved by increasing vitamin B₁₂. In our stomach, LAB play very beneficial role in checking disease causing microbes.

Question 8. Name the microbe responsible for the production of alcoholic beverages. Give example of any four alcoholic beverages.
Answer: Microbe responsible is known as Brewer's yeast - Saccharomyces cerevisiae e.g., Wine, Beer, Whisky, Brandy, Rum etc. [any four]

Question 9. Name the source of Citric acid and Butyric acid.

Answer:

Question 10. (a) What is biocontrol?
(b) What is the key belief of organic farmer?
Answer: (a) Biocontrol refers to the use of biological methods for controlling plant diseases and pests.
(b) The key belief of the organic farmer is that biodiversity furthers health.

Question 11. Give any two roles of cyanobacteria as biofertilisers.
Answer: Role of cyanobacteria as biofertilisers:
(i) They can fix atmospheric nitrogen.
(ii) They add organic matter to the soil.
(iii) They increase soil fertility (any two role).

Short Answer Type Questions

Question 12. (a) Identify the following virus:
(b) Why does the dough, used for making dosa and idli, shows puffed up appearance?
Answer: (a) Adenovirus
(b) The dough, which is used for making dosa and idli shows puffed-up appearance due to the production of CO₂ gas.

Question 13. Name the oldest food items in which microbes were used. What is the criteria for identifying its different varieties? Give one example.
Answer: Cheese, is one of the oldest food items in which microbes were used. Different varieties of cheese are known by their characteristic texture, flavour and taste, the specificity coming from the microbes used. e.g., "Swiss cheese" is ripened by bacterium Propionibacterium sharmanii.

Question 14. Who discovered Penicillin and how?
Answer: Alexander Fleming discovered Penicillin while working on Staphylococci bacteria, he observed a mould growing in one of his unwashed culture plates, around which Staphylococci could not grow. He found that it was due to a chemical produced by the mould. He named it Penicillin after the mould Penicillium notatum.

Question 15. Fill in the blanks:
(a) _______ are used in detergent formulations and are helpful in removing oily stains from laundry.
(b) _______ is used for commerical production of ethanol.
(c) Bottled juices are clarified by the use of ________ and proteases.
(d) Streptokinase produced by the bacterium Streptococcus and modified by genetic engineering is used as a ________.
(e) ________ is produced by fungus Trichoderma polysporum and is used in organ transplant patients.
(f) Statins are produced by yeast _______.
Answer: (a) Lipases
(b) Saccharomyces cerevisiae or Brewer's yeast
(c) Pectinases
(d) Clot buster
(e) Cyclosporin A
(f) Monascus purpureus

Question 16. What happens to activated sludge generated during secondary treatment?
Answer: Activated sludge - The sediment, including bacterial flocs, generated during secondary treatment is known as activated sludge. A small part of activated sludge is pumped back into the aeration tank to serve as inoculum. The remaining major part is pumped into large tanks called anaerobic sludge digester. Here other kinds of bacteria, which grow anaerobically, digest the bacteria and fungi in the sludge. During this digestion, bacteria produces a mixture of gases such as methane, hydrogen sulphide and carbon dioxide. These gases form biogas.

Question 17. Draw well labelled diagram of a bacterial virus.
Answer: A well-labelled diagram should show these parts: Head; Sheath; Collar; Tail; Plate; Pins; Prongs; Bacterialvirus.

Question 18. Write a short note on following biocontrol agents:
(a) Trichoderma (b) Baculovirus
Answer: (a) Trichoderma : Trichoderma species are free living fungi that are very common in the root ecosystems. They are effective biocontrol agents of several plant pathogens.
(b) Baculoviruses : These are pathogens that attack insects and other arthropods. The majority of baculoviruses used as biocontrol are in the genus Nucleopolyhedrovirus. These viruses are excellent candidates for species-specific narrow spectrum insecticidal applications. They have been shown to have no negative impact on plants, mammals, birds, fishes or even on non target insects.

Question 19. Explain the role of bacteria and fungi as a biofertiliser.
Answer: (a) Role of bacteria as a biofertiliser
(i) Nodules on the roots of leguminous plants are formed by the symbiotic association of Rhizobium. These bacteria fix atmospheric nitrogen into ammonia, which is used by the plants as nutrient.
(ii) Other bacteria can fix atmospheric nitrogen while free living in the soil (e.g., Azospirillum and Azotobacter), thus enriching the nitrogen content of soil.
(b) Role of fungi as biofertiliser The symbiotic association of fungi with plants is known as mycorrhiza. Many members of genus Glomus form mycorrhiza. The fungal symbiont in these associations absorbs phosphorus 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.

Long Answer Type Questions

Question 20. Define the following :
(a) Antibiotics
(b) Sewage
(c) Primary effluent
(d) Biofertilisers OR Draw a well labelled diagram of biogas plant.

Answer:

Definitions
(a) Antibiotics - These are the chemical substances, which are produced by some microbes and can kill or retard the growth of other disease causing microbes.
(b) Sewage - The municipal waste-water with major component as human excreta is known as sewage.
(c) Primary effluent - During primary treatment all solids that settles is known as primary sludge and the supernatant is known as primary effluent.
(d) Biofertilisers - These are organisms that enrich the nutrient quality of the soil. OR

Gas

Gas-holder

Dung Water (CH₄ + CO₂ + ------) Sludge

Digester

Biogas Plant

Question 21. Why secondary treatment of STP is known as biological treatment? Explain.

Answer:

Secondary treatment or Biological treatment
(i) The primary effluent is passed into large aeration tanks where it is constantly agitated mechanically and air is pumped into it.
(ii) This allows vigorous growth of useful aerobic microbes into flocs.
(iii) Flocs are the masses of bacteria associated with fungal filaments to form mesh like structures.
(iv) While growing these microbes consume major part of the organic matter in the effluent.
(v) This significantly reduces BOD of effluent. The effluent of aeration tank is then passed into a settling tank where the bacterial "Flocs" are allowed to sediment.
(vi) This sediment is known as activated sludge. The effluent from the settling tank of the secondary treatment is generally released into natural water bodies like rivers and streams.
(vii) As microbes are used during secondary treatment it is also known as biological treatment.