Based on Whitaker system, the living world is divided into five kingdoms.
  • Kingdom Monera
    • Member : Bacteria
  • Kingdom Protista
    • Members : Algae, protozoans, slime moulds
  • Fungi
    • members : Mushrooms, moulds, lichens
  • Plantae
    • Members : Plants
  • Animalia
    • members : Animals
The Study of Microorganisms : Microbiology
  • Virus : They have no cellular mechanism of their own to carry out metabolic reactions. Hence they grow and multiply undertaking the control of the genetic mechanism of our cell. As a result, virus infected cells are completely destroyed.

  • Bacteria : After entering the body they multiply by division Certain toxic substances are released into our body as a result of metabolic reactions. They either disrupt the rhythm of cellular activities or destroy the cell itself. Consequently symptoms of these disease appear.

  • Protozoa : Like bacteria, these also produce toxins which become harmful to our body. The enzymes produced by some species of protozoa destroy the epithelium of the intestine and other organs. Some other attack blood cells.

  • Fungus : The enzymes released by fungus destroy our cells. They cause many diseases.