Class 11 Biology Biological Classification Kingdom Monera

Kingdom Monera

  • Bacteria are the sole members of the Kingdom Monera.
  • Bacteria are grouped under four categories based on their shape
  • spherical Coccus
  • rod-shaped Bacillus
  • comma-shaped Vibrium
  • spiral Spirillum.


Fig. Categories of bacteria

  • Bacteria are divided into two major groups
  • Archaebacteria


  • They live in some of the most harsh habitats such as extreme salty areas called as halophiles, hot springs and so, named as thermoacidophiles, marshy areas and hence, named as
  • The can survive in extreme habitats due to a different cell wall structure.
  • Methanogens are present in the guts of several ruminant animals and they are responsible for the production of methane (biogas).


Fig. Archaebacteria 


  • Eubacteria are known as true bacteria, and are cauterized by the presence of a rigid cell wall, and if motile, a flagellum.
  • The cyanobacteria or blue-green algae have chlorophyll a similar to green plants and are photosynthetic autotrophs.
  • The cyanobacteria are unicellular, colonial or filamentous, marine or terrestrial algae, and the colonies are generally surrounded by gelatinous sheath.
  • Some of the cyanobacteria can fix atmospheric nitrogen in specialized cells called heterocyst. For example- Nostoc and Anabaena.


Fig. Anabaena

Chemosynthetic autotrophic bacteria oxidize various inorganic substances such as nitrates, nitrites and ammonia and use the released energy for their ATP production.

  • Heterotrophic bacteria are important decomposers.
  • They are helpful in making curd from milk, production of antibiotics, fixing nitrogen in legume roots.
  • Some are pathogens causing damage to human beings, crops and cause cholera, typhoid, tetanus to human being.
  • Bacteria reproduce mainly by fission, or producing spores under unfavorable conditions or by a sort of sexual reproduction transferring DNA from one bacterium to other.
  • The Mycoplasmas are organisms that completely lack a cell wall, and they are the smallest living cells known, which can survive without oxygen.

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