Microbes in Human Welfare Class 12 Notes

According to the CBSE Syllabus 2023-24, this chapter has been renumbered as Chapter 8.

Microbes or microorganisms form a significant component of the biological systems on the Earth. They are ubiquitous, present everywhere – in the soil, around us, in water, the air we breathe, and both in and on our bodies. Also, microbes are present in other animals and plants. They are so tiny, microscopic in nature, varying in shape and size. They can only be seen through the microscope. The different types of microbes are:

  • Algae
  • Bacteria
  • Fungi
  • Protozoa
  • Virus

Also See: Important Questions for Class 12 Chapter 10: Microbes in Human Welfare

For more information on Microorganisms, watch the below video

Microbes in Human Welfare

Apart from the harmful and infectious disease-causing pathogens, there are several useful microorganisms which are beneficial to humans in various ways. Some of the most important contributions of microbes to human welfare are discussed below.

In Household Products

  • Fermentation of milk to prepare yoghurt.
  • Curdling of milk to prepare curd, cheese, and paneer.
  • Fermentation of dough, which is used for making bread, idli, and dosa.

In Industrial Products

  • Production of alcoholic beverages.
  • Production of antibiotics like Penicillin and other chemical substances to kill or hamper the growth of disease-causing microbes.
  • A few chemicals, enzymes and other bioactive molecules are also produced by these microbes for various human uses.

See More: Role of Microbes in Industrial Products

In Sewage Treatment

  • Sewage is treated in sewage treatment plans(STPs) before disposing of so as to make it less polluting, which is naturally carried out by heterotrophic microbes present in the sewage. The treatment is carried out in two stages – Primary treatment, Secondary treatment or biological treatment.
  • These processes reduce the BOD(biochemical oxygen demand) of the effluent significantly. BOD is the amount of oxygen that would be consumed if all the organic matter in one litre of water were oxidized by the bacteria. The sewage water is treated until the reduction of BOD as the BOD gauges the rate of uptake of oxygen by microbes in a water sample. Therefore, BOD is a measure of the organic matter present in water. The greater the BOD of wastewater, the more its polluting potential.

In Biogas Production

  • Methanobacterium, commonly found in anaerobic sludge, facilitates sewage treatment. They are also found in the rumen of ruminants.
  • The excreta of cattle, known as gobar, is bacteria-rich. Hence dung can be used for the generation of biogas, commonly referred to as gobar gas.

As Biocontrol Agents 

  • The utilization of biological methods to control plant pests and diseases is referred to as biocontrol which has been achieved through chemicals – pesticides and insecticides.
  • The use of biocontrol measures will reduce the dependence on toxic chemicals and pesticides to a greater extent.
  • Biological farming promotes life forms such as the inhabiting of the field, pests and predators, life cycles, and feeding patterns that will help in developing suitable means of biocontrol.
  • Microbial biocontrol agents example – Bacillus thuringeinsis, available as dry spores, sprayed on vulnerable plants.
  • Genetic engineering developments have enabled scientists to release B. thuringiensis toxins genes into plant bodies thereby making them resistant to attacks by insect pests. Example – Bt-cotton.
  • Most of the baculoviruses used as biological control agents are in the genus Nucleopolyhedrovirus.

Microbes are also used as biofertilizers.

Few Important Questions

  • What are microbes?
  • What is fermentation?
  • List out the uses of microorganisms in agriculture.
  • What is biogas? Explain how microbes are used in the production of biogas.
  • What is sewage? Write the difference between primary and secondary sewage treatment.

Learn more about microorganisms, their types, applications and their benefits to humans from the topics given below:

Microbes Biocontrol Agents
Antibiotics Useful and Harmful Microorganisms

Frequently Asked Questions on CBSE Class 12 Biology Notes Chapter 10 Microbes in Human Welfare


What are the uses of microbes?

Microorganisms help in the production of many food items, making medicines, keeping the environment clean, manufacturing and in research.


What are the types of microbes?

The major groups of microorganisms are bacteria, archaea, fungi (yeasts and molds), algae, protozoa, and viruses.


What is nitrogen fixation?

Nitrogen fixation is the process by which nitrogen is taken from its molecular form in the atmosphere and converted into nitrogen compounds useful for other biochemical processes.


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