The monera kingdom is the set of microorganisms that have a single prokaryotic type cell.
The monera kingdom is the set of microorganisms that are made up of a single prokaryotic cell , lacking a defined nucleus. The notion, however, is not used much today, as the concept of a prokaryotic kingdom is preferred.
Living beings can be classified in different ways. This classification, in fact, has changed throughout history, adapting to scientific discoveries and the different positions of experts.
Discovery of the monera kingdom
The German naturalist Ernst Haeckel ( 1834 – 1919 ) is usually noted as the first scientist to speak of the kingdom monera or mónera . In 1866 , Haeckel divided living beings into animals , plants and protists . In this last kingdom he included a set of organisms called moneras , which would be the simplest of all. Eukaryotes and prokaryotes were also included in this classification.
It should be noted that in the etymology of this term, which derives from a Greek word whose pronunciation is close to "moneres" , the idea of simplicity is found and that is why it was chosen to name these organisms.
In the 1920s , it was the Frenchman Édouard Chatton ( 1883 – 1947 ) who distinguished between prokaryotes and eukaryotes . From then on, the Monera kingdom began to be associated with the first.
Bacteria belong to the kingdom monera.
The concept today
Currently, the theory of the five kingdoms predominates: living beings are divided into animals , plants , fungi , eukaryotes and prokaryotes . The classification of monera was linked to the clade of prokaryotic organisms, which are the smallest cellular organisms, lacking a cell nucleus and organelles.
The lack of use of the idea of kingdom monera has to do with the distinction that is currently made between bacteria and archaea , two sets of different characteristics. In this way the entire system of classification of organisms is modified.
Archaea are a group of single-celled microorganisms that, like bacteria, have a prokaryotic morphology, that is, they do not have a nucleus or, generally, membranous organelles inside. Since they are essentially different from bacteria, they have their own kingdom (or domain). In the past, when they were included in the kingdom Monera, scientists called them archaebacteria , a name that has since fallen into disuse.
The word monera is still used to talk about bacteria in general; In other words, it serves to refer to the evolutionary branch (the clade ) of which all cellular organisms that do not have a defined nucleus are part, that is, the prokaryotes, the oldest forms of life discovered by humans.
Characteristics of the monera kingdom
We can say that the Monera kingdom has the following characteristics, added to those already mentioned in previous paragraphs:
- Its size, the smallest of any cellular organism, can be between 3 and 5 micrometers (a unit of length that is equivalent to one millionth of a meter).
- Regarding their cellular level, they are generally unicellular organisms.
- They do not have mitochondria, plastids or endomembranous systems of any type.
- Their diet is osmotrophic, that is, they acquire the nutrients they need in the form of dissolved substances, through the process known as osmosis , and it can occur heterotrophically (if they feed on substances that other organisms have synthesized) or autotrophically (if they They themselves synthesize their own organic substances, necessary for metabolism, starting from inorganic substances).
- They require a minimal level of oxygen for their survival.
- They reproduce mainly through binary fission , asexually. Prokaryotic organisms do not undergo mitosis . They exchange or combine genetic material to achieve the formation of a new specimen.
- They may have flagella to facilitate their locomotion.