VBQs Microbes in Human Welfare Class 12 Biology

VBQs for Class 12

VBQs Microbes in Human Welfare Class 12 Biology with solutions has been provided below for standard students. We have provided chapter wise VBQ for Class 12 Biology with solutions. The following Microbes in Human Welfare Class 12 Biology value based questions with answers will come in your exams. Students should understand the concepts and learn the solved cased based VBQs provided below. This will help you to get better marks in class 12 examinations.

Microbes in Human Welfare VBQs Class 12 Biology

Very Short Answer Type Questions

Question. Name the types of association that the genus Glomus exhibits with higher plants.
Answer :
 Symbiosis / Mycorrhiza / Mutualism. 

Question. Write the significance of nucleopolyhedrovirus in pest management.
Answer :
 Nucleopolyhedroviruses are the effective biocontrol agent. They are species specific and have narrow spectrum insecticidal application having no negative impact on non target beneficial organisms.
They play significant role in pest management. 

Question. Name any one symbiont which serves as a biofertilizer. Mention its specific role.
Answer :
 Rhizobium, a root nodule bacterium of legumes is a symbiont. It fixes nitrogen symbiotically and thus help the plants in obtaining their nitrogen nutrition and therefore serve as a biofertilizer. 

Question. Name any two free living nitrogen fixing bacteria.
Answer :
 Azotobacter and Azospirillum. 

Short Answer Type Questions

Question. Name a genus of baculovirus. Why are they considered good biocontrol agents ?
Name the genus to which baculoviruses belong.
Describe their role in the integrated pest management programmes. 
Answer :
Species specific, narrow spectrum insecticidal application, no negative impact on non-target organisms. 
Detailed Answer :
Nucleopolyhedrovirus is a genus of baculoviruses.
They are useful as they are good biocontrol agents.
They are species specific, narrow spectrum bioinsecticides. They control only species specific pest, do not affect non target organisms / beneficial insects are conserved / they aid in IPM problems / no negative impact on plants or other animals.
Therefore, they are considered as an important component of integrated pest management programme. 

Question. Explain the significant role of the genus Nucleopolyhedrovirus in an ecological sensitive area. 
Answer :
 The genus Nucleopolyhedrovirus include baculoviruses which are insecticidal and therefore used as biocontrol agents. They have narrow spectrum, insecticidal application (IPM). They have no negative impact on plants / mammals / birds / fish / even non target insects. They are desirable in integrated pest management programme. 

Question. What is the pathogenic property of baculovirus, used as a biological agents ? Name the genus of these organisms.
Answer :
 Attacks insect and other arthropods. 
Detailed Answer :
Baculoviruses are pathogens that attack insects and other arthropods. The majority of baculoviruses used as biological control agents belongs to the genus nucleopolyhedrovirus.

Question. How do mycorrhizae help the plants to grow better? 
How do mycorrhiza act as biofertilizers ? Explain.
Name a genus of fungi that forms a mycorrhizal association with plants.
Answer :
 Mycorrhiza refers to symbiotic association between the fungus and the root of higher plants. These fungi in these associations absorb water, phosphorus, nitrogen, potassium, calcium from soil and pass it to the plant. The fungus brings about the solubilization of organic matter of soil humus, release of inorganic nutrients absorption and their transfer to roots. The genus Glomus forms a mycorrhizal association with plants. 

Question. Given below is a list of six micro-organisms. State their usefulness to humans.
(i) Nucleopolyhedroviruses
(ii) Saccharomyces cerevisiae
(iii) Monascus purpureus
(iv) Trichoderma polysporum
(v) Penicillium notatum
(vi) Propionibacterium sharmanii
Answer :
 (i) Nucleopolyhedrovirus : It is a biological control agent and is a species-specific insecticide.
(ii) Saccharomyces cerevisiae : It is used to ferment bread dough and used in the preparation of ethanol.
(iii) Monascus purpureus : It is commercialised as blood cholesterol lowering agent.
(iv) Trichoderma polysporum : It produces cyclosporin A, which act as an immunosuppressive agent in organ transplant patients.
(v) Penicillium notatum : It is a source of penicillin, an antibiotic.
(vi) Propionibacterium shermanii : It is used in the preparation of cheese for texture, flavour and taste. 

Question. Explain the role of Baculoviruses as biological control agents. Mention their importance in organic farming.
Explain the significant role of the genus Nucleopolyhedrovirus in an ecological sensitive area. 
Answer : The role of Baculoviruses : 
Baculoviruses are pathogens that attack insects and other arthropods. The majority of baculoviruses used as biological control agents are in the genus Nucleopolyhedrovirus. These viruses are excellent species-specific, biocontrol agents have narrow spectrum insecticidal applications. They have been shown to have no negative impacts on plants, mammals, birds, fish or even on non-target insects.
Importance in organic farming :
(i) Baculoviruses are known to control pests like potato beetles, aphids and corn borers.
(ii) Entomopox virus is another baculovirus which adversely affects the rate of development of grasshopper and the amount of food it eats.

Question. (i) Why do farmers prefer biofertilizers to chemical fertilizers these days ? Explain.
(ii) How do Anabaena and Mycorrhiza act as biofertilisers ? 
Answer :
 (i) Farmers prefer biofertilisers to chemical fertilizers because :
(a) They help to get high yield of crops by making the soil rich with nutrients and useful microorganisms necessary for the growth of the plants.
(b) Chemical fertilizers make the environment polluted by releasing harmful chemicals and show biological magnification.
(c) Biofertilisers destroy only those harmful components from the soil that cause diseases in the plants.
(d) Biofertilisers are environment friendly and protect the environment against pollutants.
(ii) Fungi are known to form symbiotic association with plants called mycorrhiza. Many members of the genus Glomus forms mycorrhiza. The fungal symbiont in this association absorbs phosphorus from soil. Arbuscular mycorrhizal fungi play a vital role as a phosphatic biofertilizer.
Cyanobacteria are autotrophic microbes widely distributed in aquatic and terrestrial environments, many of which can fix atmospheric nitrogen e.g. Anabaena, Nostoc, Oscillatoria etc.

Question. (a) Organic farmers prefer biological control of diseases and pests to the use of chemicals for the same purpose Justify.
(b) Give an example of a bacterium, a fungus and an insect that are used as biocontrol agents.
Answer :
 (a) (i) Reduces dependence on toxic chemicals.
(ii) Protects our ecosystem or environment.
(iii) Protects and conserves non-target organisms / they are species – specific.
(iv) These chemicals being non-biodegradable may pollute the environment permanently.
(v) These chemicals being non-biodegradable may cause biomagnification.
(b) Bacteria : Bacillus thuringiensis. 
Fungus : Trichoderma. 
Insect : Ladybird / Dragonfly / Moth or any other correct example. 

Question. Baculoviruses are good example of biocontrol agents. Justify giving three reasons.
Answer :
 i. Species specific / narrow spectrum insecticidal application. 
ii. They have no negative impact on plants / mammals / birds / fish / non target insects. 
iii. They are beneficial for IPM (Integrated Pest Management ) / Pest Management Programme.

Question. An organic farmer relies on natural predation for controlling plant pests and diseases. Justify giving reasons why this is considered to be holistic approach. 
Answer :
 Organic farming is holistic approach for controlling plant pest because it seeks to develop an understanding of the interactions amongst the organisms in the ecosystem.
Organic farmers do not try to completely eradicate the pest but keep them at manageable levels. A complete eradication of the pest is not beneficial and also not desirable because many beneficial predatory and parasitic insects can not survive without them. 

Long Answer Type Questions

Question. (i) How does Bacillus thuringiensis act as a biocontrol agent for protecting Brassica and fruit trees ? Explain. 
(ii) (a) List the components of biogas.
(b) What makes methanogens a suitable source for biogas production ?
Answer :
(i) Bacterium Bacillus thuringiensis (Bt) are available in sachets as dried spores, mixed with water and sprayed onto vulnerable plants, these are eaten up by the insect larvae, the toxins are released in the gut and larva gets killed.
(ii) Methane, H2S, CO2, H2
(iii) Methanogens grow anaerobically on cellulosic material, produce large amount of methane, alongwith CO2 & H2