Modern classification of living organisms , Kingdom ( Monera and Protista )

Attempts of classification of living organisms :

The Latin philosopher : Aristotle ( more than 2300 years ago ) , He was the first who classified animals into red-blooded animals and bloodless animals , Plants into trees , shrubs and weeds .

The scientist : Carolus Linnaeus ( 1700 ) , He established the traditional classification system that classified living organisms into two kingdoms only , which are animal kingdom and plant kingdom .

The scientist : Robert Whittaker ( 1969 ) , He established the modern system of classification where living organisms were classified into five kingdoms , where are Monera , Protista , Fungi , Plantae and Animalia , This system is the conventional system in the scientific communities .

There are some organisms that are difficult to classify according to Whittaker classification , They are viruses , viroids and prions .

Kingdom Monera

Kingdom Monera

Kingdom : Monera

General characteristics of kingdom Monera :

Mode of living : It may live individually or in colonies .

Structure : Its body consists of one cell ( unicellular organisms ) .

The nucleus : It is prokaryotic , It does not surrounded by a definite nucleus and the genetic material is found in cytoplasm and not surrounded by a nuclear membrane .

Cell wall : It is devoid from cellulose or pectin .

Cytoplasm : is lack of many membranous organelles such as : mitochondria , plastids , Golgi apparatus and endoplasmic reticulum .

Kingdom Monera is classified into two different groups , which are Archaebacteria and Eubacteria .


  • Habitat : Most of them survive in harsh environment conditions , such as Hot springs , Environment with no oxygen and High salty water .
  • They differ from Eubacteria in structure of both cell membrane and cell wall .


  • Habitat : They live everywhere and in all earth’s environment , such as Air , Land and Water .
  • Nutrition : Some are autotrophic such as Cyanobacteria , such as Nostoc and others are heterotrophic .
  • Reproduction : is asexually by binary fission .
  • Shapes : They have several shapes ( forms , such as Spherical-shaped , Rod-shaped and Spiral-shaped .

Bacteria are classified in a separate kingdom ( Monera ) because they are characterized by the following characteristics :

They are unicellular organisms , They have a cell wall and their genetic material is not surrounded by a nuclear envelope ( nuclear membrane ) .


They are very tiny bacteria , their size is about 20 : 2oo nanometers , Scientists disagree in considering them as crystalline structures or a new form of life , They grow slowly inside the living cell .

Their shape changes during their stages of growth , They are more resistant than the normal bacteria where they can protect themselves from the defence system of the body by secreting stone shields surrounding them as a capsule .

Researchers arrived to that this kind of bacteria is a main cause in the formation of kidney stones , atherosclerosis and inflammation of the prostate .

Kingdom : Protista

General characteristics of kingdom protista :

They are eukaryotic organisms , Their structure is not complex as plants and animals , Some of them have cell walls and plastids , Most of them are unicellular and the little are multicellular .

Kingdom protista is classified into four phyla which are Phylum Protozoa , Phylum Euglenophyta , Phylum Chrysophyta and phylum Pyrrophyta .

Phylum : Protozoa

Habitat : Some are free living , individually or in colonies , in fresh and salt water , as well in moist soils , Others parasitize plants and animals causing diseases .

Structure : They are unicellular and microscopic animal-like organisms .

Reproduction : They reproduce sexually and asexually .

Protozoa is classified into four classes depending on the mean of locomotion which are :

Class Sarcodina

Mean of locomotion : Pseudopodia ( Temporary extensions from the body ) such as Amoeba .

Class Ciliophora

Mean of locomotion : Cilia ( surrounding the body ) , such as Paramecium .

Class Flagellata

Mean of locomotion : Flagella , Trypanosoma presents between blood corpuscles of an infected person with sleeping sickness ( Parasitizes human and infects him with sleeping sickness ) , such as Trypanosoma .

Class Sporozoa

( They produce phases called spores ) , They have no mean of locomotion , They parasitize the human and infects him with malaria disease .

Sleeping sickness

It is one of widespread diseases in the tropical regions , It is caused by Trypanosoma parasite that is transmitted by tsetse fly , when it bites a human , Its symptoms include fever , heavy sweat , headache , hallucination , weakness and tendency to sleep , Without treating the patient in the proper time , he goes into coma which leads to death .

Phylum : Euglenophyta

Structure : Unicellular organisms

Cytoplasm : Contains chloroplasts which perform photosynthesis .

Mean of locomotion : Move by flagella .

Example : Euglena .

Phylum : Chrysophyta

Structure : Most of them are unicellular and called diatoms , They are characterized by : 

They have glass-like walls containing silica , They are considered as an important source of food for fish and other marine animals .

Phylum : Pyrrophyta

Habitat : They live in seas and oceans , where they form a great portion of phytoplanktons , They contain a red pigment , acquiring them a red colour beside the chlorophyll pigment .

Example : Dinoflagellates that represent the largest group of phylum pyrrophyta and they move by two flagella .

Red tide phenomenon :

It is a natural phenomenon occurs in water of seas and oceans where water is coloured red and this is accompanied with death of thousands of fishes .

The cause of this phenomenon is attributed to the enormous increase in numbers of dinoflagellates when water becomes warm with a plenty of nutrients , There organisms reproduce very rapidly and secrete toxins kill fishes .

General characteristics of Kingdom Fungi and Kingdom Plantae

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