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 , 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
General characteristics of kingdom Monera :
It may live individually or in colonies , Its body consists of one cell ( unicellular organisms ) , 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 .
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 .
Most of them survive in harsh environmental 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 .
They live everywhere and in all earth’s environment , such as Air , Land and Water , Some are autotrophic such as Cyanobacteria , such as Nostoc and others are heterotrophic , Reproduction is asexually by binary fission , 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
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 , They are unicellular and microscopic animal-like organisms , They reproduce sexually and asexually , Protozoa is classified into four classes depending on the mean of locomotion which are :
Mean of locomotion : Pseudopodia ( Temporary extensions from the body ) such as Amoeba .
Mean of locomotion : Cilia ( surrounding the body ) , such as Paramecium .
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 .
( They produce phases called spores ) , They have no mean of locomotion , They parasitize the human and infects him with malaria disease .
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 .
They are unicellular organisms , Cytoplasm contains chloroplasts which perform photosynthesis , They move by flagella , Example : Euglena .
Phylum : Chrysophyta
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
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 :
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.