This set of Class 12 Biology Chapter 10 Multiple Choice Questions & Answers (MCQs) focuses on “Microbes as Biocontrol Agents”.
1. What does biocontrol refer to?
a) Use of biological methods for controlling plant diseases
b) Use of chemical methods for controlling plant diseases
c) Use of morphological methods by the plants to control the attack of pathogens
d) Use of physical methods by the plants to control the attack of pathogens
Explanation: Biocontrol refers to the use of biological methods for controlling plant diseases and pests. Fertilisers of biological origin are of two types-manures and bio-fertilizers.
2. Which of the following is generally not polluted by the use of chemical fertilisers?
Explanation: The chemical fertilisers have been polluting our environment-soil, ground, water, fruits, vegetables and crop plants. Our soil is also polluted through our use of weedicides to remove weeds.
3. What is the method of controlling pests in agriculture by the organic farmer?
a) Chemical fertilizers
b) Natural predation
c) Morphological method
d) Physiological method
Explanation: In agriculture, there is a method of controlling pests that relies on natural predation rather than introduced chemicals. A key belief of the organic farmer is that biodiversity furthers health and the use of chemicals sometimes kills both useful and harmful life forms.
4. The more variety a landscape has, the more sustainable it is.
Explanation: The more variety a landscape has, the more sustainable it is. The organic farmer works to create a system where pests are not eradicated but instead are kept at manageable levels by a complex system of checks and balances.
5. Which of the following is not true regarding biological farming?
a) Farmers understand the webs of interaction among organisms
b) Use of biocontrol measures will increase our dependence on chemical fertilizers
c) Farmers become familiar with the various life forms that inhabit the field
d) Farmers become aware of the life cycles and feeding habits of organisms
Explanation: In biological farming, farmers understand the webs of interaction between the myriad of organisms that constitute the field flora and fauna. They also become familiar with the life cycles, feeding habits, pests and predators of various life forms that inhabit the field. Thus, the use of biocontrol measures greatly reduces our dependence on chemical fertilizers.
6. What are the dragonflies use to get rid of?
d) Honey bees
Explanation: The dragonflies are very useful to get rid of mosquitoes. The very familiar beetle with red and black markings-the Ladybird is useful to get rid of aphids.
7. What are biocontrol agents for controlling butterfly caterpillars?
a) Bacillus thuringiensis
c) Acetobacter aceti
d) Treponema palladium
Explanation: Biocontrol agents are the organisms which are the natural enemies of insect pests or the disease-causing microbes which can be used for our own benefit. For example, bacteria Bacillus thuringiensis which can be introduced to control butterfly caterpillars.
8. How is Bacillus thuringiensis available to be sprayed on plants?
a) In the form powder
b) In the form of log
c) In the form of dried spores
d) In the form of wet spores
Explanation: Bacillus thuringiensis is often available in sachets as dried spores which are mixed with water and sprayed onto vulnerable plants such as brassicas and fruit trees, where they are eaten by the insect larvae.
9. When larva eats the bacteria, then in the head of the larvae, the toxin is released.
Explanation: When the bacteria are eaten by the larva, then in its gut, the toxin is released and the larva gets killed. The bacterial disease will kill the caterpillars, but leave other insects unharmed.
10. Which of the following crop has been developed by genetic engineering in India?
Explanation: Due to the development of various methods of genetic engineering, in the last decade or so, scientists have introduced Bacillus thuringiensis toxin genes into the plants. Bt-cotton is one such example, which is being cultivated in some states of our country.
11. Which of the following statements is incorrect regarding Trichoderma?
a) It is a bacterium
b) Very common in root ecosystems
d) Effective biocontrol agents
Explanation: Trichoderma species are free-living fungi that are very common in the root ecosystems. They are effective biocontrol agents of several plant pathogens.
12. For which of the following, Baculoviruses are not the excellent candidates?
a) Species-specific applications
b) Narrow spectrum applications
c) Insecticidal applications
d) Broad-spectrum applications
Explanation: Baculoviruses are excellent candidates for species-specific, narrow spectrum, insecticidal applications. The majority of baculoviruses used as biological control agents are in the genus Nucleopolyhedrovirus.
13. On which of the following does the baculoviruses attack?
Explanation: Baculoviruses are pathogens that attack insects and other arthropods. They have shown no negative impacts on plants, mammals, birds, fish or even on non-target insects.
14. What is the full form of IPM?
a) Indian Pests Management
b) Integrated Pest Management
c) Integrated Plant Management
d) Indian plant management
Explanation: IPM stands for Integrated Pest Management. Biocontrol agents are especially desirable when beneficial insects are being conserved to aid in an overall IPM programme, or when an ecologically sensitive area is being treated.
15. Which of the following is the first developed bio-insecticide?
d) Nicotine Sulphate
Explanation: Sporeine was developed in Germany and is the first commercially used bio-insecticide. Its other trade names are Dipel, Biostol and Thuricide.
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