We explain Monera Kingdom Examples, the origin of the term, its characteristics, and classification with taxonomy.
What is the monera kingdom?
The monetary kingdom is one of the large groups in which biology classifies living beings, such as the animal, plant, or fungi kingdom. Only in this case, it includes the simplest and most primitive life forms that are known, and therefore can be very diverse in nature, although they have common cellular characteristics: they are unicellular and prokaryotic.
Much is ignored regarding the appearance of eukaryotic life, something key in the development of multicellular beings, from eukaryotes that in ancient times belonged to the monetary kingdom. One of the most accepted theories proposes that a pair of these unicellular organisms would have developed a very narrow symbiosis, which led one to be part of the body of the other, taking care of some internal functions. However, the monetary kingdom is phylogenetically prior to all the others that exist.
However, the term currency is currently in disuse. Other classification models are preferred, such as the one that proposes three domains: eukarya (eukaryotes), archaea (archaeobacteria), and bacteria (bacteria), the latter two being what previously formed the monetary kingdom.
Origin of the term Monera
The term monera has its roots in the Greek moneres (“simple”), and has been used over time, its specific meaning changed. In principle, it was proposed by Ernst Haeckel in 1866, who was the first to propose a classification of life-based on evolutionism. In it, he distinguished three kingdoms: animal, plant, and protist, gathering in the last all the “simple” or microscopic forms, among which were the minerals or more: the base of the evolutionary tree.
Subsequently, Edóard Pierre Chatton discovered in 192 that the bacteria did not possess a cell nucleus. Thanks to this, it was possible to distinguish between prokaryotes and eukaryotes, that is, without and with a cell nucleus. As a result, in 1939, Fred Alexander Barkley used the term “monera” to refer to prokaryotes: a new kingdom that was divided into Tracheophyta (cyanobacteria) and schizophyta (bacteria).
Later in history, in 1956, Herbert Copeland reorganized the kingdoms of life into four categories: animals, plants, protists (where the simple eukaryotes were), and minerals (where the prokaryotes were). To this classification, Robert Whittaker would add in 1969 the kingdom of fungi (Fungi) and it is this last version, revised in 2000, that we use today.
Characteristics of the monetary kingdom
The species of the monetary kingdom can be very diverse in their morphology and life habits, but they have minimal characteristics of evolutionary and biological simplicity that unify them, such as:
- They measure 3 to 5 micrometers. It is the smallest living being that exists on the planet.
- They are unicellular and prokaryotic. These are unicellular organisms, that is, autonomous cells that do not form tissues, or colonies, or more complex organisms, and that also lack a cell nucleus where their DNA rests.
- Without organelles of any kind. Unlike eukaryotic cells, much larger and more complex inside, monerans are cells without “internal organs” such as mitochondria or plastids, although they do have simple structures that fulfill internal processes.
- Asexual reproduction. The processes of reproduction of the moneras do not involve the meiosis or production of gametes (sexual cells), but instead involve binary fusion and other processes in which an individual gives rise to two identical ones.
- Circular DNA The DNA of these species is found loose in the cytoplasm and circulates instead of a double helix, being much simpler and smaller.
- Nutrition. Many coins are heterotrophic (saprophytic, parasitic, or symbiotic), that is, they feed on organic matter in the environment; but they can also be autotrophic (photosynthetic or chemosynthetic), taking advantage of sunlight or the chemical reactions of the environment to make their own food.
Classification of the monera kingdom
The coins cover three large groups, which are:
- Eubacteria Called “true bacteria,” have a single chromosome and are the simplest known cell life forms on Earth. Depending on their shape, they can be classified into bacilli (cane shape), coconuts (round shape), spirals (corkscrew shape), and vibrios (comma shape).
- Archaebacteria Radically different forms of bacteria, which survive by taking advantage of chemical resources from extreme habitats: salinity, heat, pH, etc. They are thought to be so numerous that they make up 20% of the earth’s biomass.
- Blue-green algae. Known as cyanobacteria, they perform photosynthesis in a slightly different way from plants, and their presence in most habitats allows them to form symbiotic relationships with other species.
Taxonomy of the Monera Kingdom
This kingdom was initially subdivided into two: bacteria and archaea, each with its own subclassification. But after the discovery of ribosomal DNA, a new classification based on four distinct groups could be established:
- Mendosicutes, arches, or archaebacteria. Arches mean “ancient” since initially they were supposed to be a kind of proteobacteria. It is difficult to classify them since they are really very small, but they present metabolic pathways and internal processes much more similar to eukaryotes than to other traditional prokaryotes.
- Mollicutes, Tenericutes, or mycoplasmas. A type of mostly parasitic bacteria, whose notorious feature is that they lack the cell wall present in most bacteria and that they have a form and a genetic code of the simplest known.
- Gracilicutes or gram-negative bacteria. A supergroup of bacteria that make up the Spirochaetes, Proteobacteria, Planctobacteria, and Sphingobacteria groups, possessing a thin skin of murein and a double plasma membrane. That is why they are not susceptible to Gram staining.
- Firmicutes or gram-positive bacteria. Endobacterial calls have a very thick cell wall and bacillus or coconut. In this group are gram-positive bacteria, which respond to Gram tincture by acquiring blue or violet color, and are associated with fermentation processes of organic matter.
Importance of the monetary kingdom
It is the first kingdom to exist when life originated in one way or another on the planet. Their simplicity allowed them to emerge in the hostile initial conditions of the Earth, and even today it is possible to find coins in habitats hostile to other life forms. Thus, to understand money is to study the very origin of life. As if that were not enough, many of them are infectious agents of the human being, whose understanding will allow to fight diseases better and save lives.
Examples of members of the Monera kingdom are the various bacteria known to mankind, such as Escherichia coli, a gram-negative bacillus that often parasites the human digestive tract, or Clostridium tetani, a very common bacterium in the soil and digestive tract of the animals, which tetanus can cause in humans, a lethal disease, when entering the blood.
Viruses constitute a very particular case. Despite being very simple and primitive biological forms, they are not among the moneras and are classified independently. This is because, although most viruses are much more basic than the simplest bacteria, they depend on them to reproduce, injecting them with their parasitic genetic material to force them to synthesize their proteins . That is, viruses cannot live without cells to infect. There is even scientific debate about whether viruses are life forms, or if they are something totally different.