[Biology Class Notes] on Monera Pdf for Exam

In biology, monera is a kingdom comprised of prokaryotes that are single – celled organism without a true nucleus. This kingdom monera is one of the earliest groups of organism on earth. In this particular kingdom, it has been observed that the organisms have naked DNA which creates a clump which is termed as the nucleoid. The organisms belonging to the other kingdom are known to have DNA enclosed in a nucleus. The organisms belonging to the kingdom monera are prokaryotes, like bacteria and do not have membrane bound organelles. The organisms are microscopic and are generally found living in moist environments. For instance, the organisms belonging to this kingdom can be found within animal bodies, plants, deep oceans and hot springs.

                                                            

Characteristics of Monera

In kingdom monera, some organisms are found to be autotrophic who are responsible for the preparation of their own food either by chemosynthesis (for instance, conducting nitrification of Bactria in the cycle of nitrogen) or by photosynthesis. The remaining are heterotrophic and are either existing as saprophytic decomposers or as parasitic bacteria. The organic matter is fed by the saprophytic decomposers found in the soil and the parasitic bacteria derive their food from a living host. The organisms are unicellular and contain 70S ribosomes.

The organism belonging to this group has different means of mobility like movement of organisms using flagella. Or they may secret slime so that they can glide or use axial filaments to rotate themselves. The organisms do not have organelles like centrosome, endoplasmic reticulum, lysosomes, Golgi bodies, mitochondria, plastids etc.

The organisms of the monera kingdom are known to reproduce asexually by binary fission. This process does not allow any noticeable genetic diversity. This is due to the fact that the daughter cells receive genetic information which is identical to that of its parent’s. Another known method of reproduction among this group is budding.

Some organisms in the kingdom monera have the ability to surround themselves by a capsule for the purpose of defending themselves. The defense is against adverse conditions and threats like desiccation and phagocytosis by white blood cells. The cells are coated and are dehydrated partially and thus turning into an endospore which is a dormant phase. The endospore will return to being an active and normal cell when the conditions are favourable for it. The cell walls of the organisms in kingdom monera are made up of peptidoglycan.

Bacteria 

Bacteria are microscopic organisms which have the ability to survive in very diverse environments. The bacteria are known to be both beneficial and harmful. They have a simple structure with very few cell organelles and no nucleus is present. The bacteria have two protective coverings which surround them and they are the outer cell wall and inner cell membrane. It has been found that some of the bacteria use capsule to be covered up, whereas, some other, for instance Mycoplasma do not possess a cell wall. 

The surface of the bacteria is covered by shirt whip – like extensions called pili. The long which like structure that extends from the body is called flagella. The bacteria are known to demonstrate both autotrophic and heterotrophic modes of nutrition. Inorganic substances provide nutrition to the autotrophic bacteria. They draw hydrogen and carbon from the carbon dioxide present in the atmosphere, hydrogen, hydrogen sulphide and ammonia. The heterotrophic bacteria in the other hand are dependent on external organic materials for deriving their food. They can either be saprotrophs, symbionts and / or parasites. 

Bacterial Shape

The bacteria have different shapes and they are discussed below:

Bacilli – These bacteria are rod – shaped and may or may not have flagella.

Cocci – The bacteria are either oval or spherical in shape. They can be staphylococcus (in clusters), streptococcus (in chains), tetracoccus (in fours), 

diplococcus (in pairs) and micrococcus (single).

 
Vibrios – These bacteria are kidney – shaped or comma shaped bacteria and the flagella is found at only one or sometimes at both ends.

Spirillum – The spirillum are the spiral or coiled shape bacteria. These bacteria are rigid due to the spiral structure and flagella may be present only at one or at both ends.

Filament – In this case, the body are found to have small filaments like the fungal mycelia.

Budded – The body of this bacteria are swollen at places.

Stalked – This type of bacteria possesses a stalk in its body.

Classification of Monera

The kingdom Monera has been divided into three sub – kingdoms known as Cyanobacteria, Eubacteria and Archaebacteria. 

Archaebacteria – in the most extreme habitats the Archaebacteria are found. They are the most ancient group of bacteria living. Their habitat includes halophiles i.e., salty areas, thermoacidophiles i.e., hot springs and methanogens i.e., marshy areas. The structures of their cell walls are found to be different from other groups of bacteria and this helps them in surviving in such conditions. The mode of nutrition among Archaebacteria is autotrophic and the nucleotide sequences of their t – RNA and r – RNA are unique. 

Eubacteria – This group of bacteria are also termed as “true bacteria”. They have rigid cell walls which are formed of peptidoglycans. The mode of locomotion is flagella. A few bacteria are known to contain short appendages on the surface of the cell and are known as pili.

Cyanobacteria – The Cyanobacteria are also known as blue – green algae and mode of nutrition is photosynthesis. These types of bacteria are commonly available in the aquatic regions and some can even fix atmospheric nitrogen. Anabaena is a type of Cyanobacteria.

Summary

Monera is a kingdom comprised of prokaryotes that are single – celled organism without a true nucleus.

The organisms have naked DNA which creates a clump which is termed as the nucleoid.

The organisms belonging to this kingdom can be found within animal bodies, plants, deep oceans and hot springs.

Organisms are found to be autotrophic who prepare their own food either by chemosynthesis or by photosynthesis.

Bacteria are microscopic organisms which have the ability to survive in very diverse environments.

The kingdom Monera is broadly classified into three sub – kingdoms known as Archaebacteria, Eubacteria and Cyanobacteria.