Biology Class 12 NCERT Solutions: Chapter 10 Microbes in Human Welfare Part 5 (For CBSE, ICSE, IAS, NET, NRA 2022)

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Q. 14 Arrange the following in the decreasing order (most important first) of their importance, for the welfare of human society. Give reasons for your answer. Biogas, Citric acid, Penicillin and Curd

Answer:

  • The order of arrangement of products according to their decreasing importance is:

Penicillin-Biogas − Citric acid − Curd

  • Penicillin is the most important product for the welfare of human society. It is an antibiotic, which is used for controlling various bacterial diseases.
  • The second most important product is biogas. It is an eco-friendly source of energy. The next important product is citric acid, which is used as a food preservative.
  • The least important product is curd, a food item obtained by the action of lactobacillus bacteria on milk.
  • Hence, the products in the decreasing order of their importance are as follows: Penicillin-Biogas − Citric acid − Curd
Biogas

Q. 15 How do biofertilisers enrich the fertility of the soil?

Answer:

  • Bio-fertilizers are living organisms which help in increasing the fertility of soil. It involves the selection of beneficial micro-organisms that help in improving plant growth through the supply of plant nutrients.
  • These are introduced to seeds, roots, or soil to mobilize the availability of nutrients by their biological activity.
  • Thus, they are extremely beneficial in enriching the soil with organic nutrients. Many species of bacteria and cyanobacteria have the ability to fix free atmospheric nitrogen.
  • Rhizobium is a symbiotic bacteria found in the root nodules of leguminous plants.
  • Azospirillium and Azotobocter are free living nitrogen-fixing bacteria, whereas Anabaena, Nostoc, and Oscillitoria are examples of nitrogen-fixing cyanobacteria.
  • Biofertilisers are cost effective and eco-friendly.
Fertility of Soil

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