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61. Define BOD and COD.

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62. Do you think microbes can be used as source of energy ? If yes, how ?

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63. Microbes can be used to lessen the burden of use of chemical pesticides. Explain how this can be accomplished.

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64. Write a short note on natural insecticides.

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65. What is biopesticide ? Give a few examples.

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66. What for Nucleopolyhydro viruses are being used now a days?

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Biofertilizers are substances which contain micro-organisms that bring about soil nutrient enrichment by their biological activity.

Micro-organisms used are Bacteria, cyanobacteria and fungi.

Symbiotically nitrogen fixing organisms

1. Rhizobium leguminosarum.

2. Nostoc (Cyanobacteria).

Asymbiotically nitrogen fixing organisms

1. Free living aerobic bacteria—Azotobacter

2. Free living photosynthetic—Chlorobium.

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68. Why are biofertilizers or biopesticides preferred to chemical fertilizers or pesticides ?

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69. What is biogas ?

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70.

Why is the biogas plant usually built in the rural area?

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