The Monera Kingdom: Prokaryotic Life and Classification

Understanding Species in Biology

A taxonomic category, a species is defined as a set of natural populations that can interbreed, either in reality or potentially, and which are reproductively isolated from other similar groups. When individuals can cross, it means their descendants are also fertile. The term "potentially" relates to natural conditions that might prevent crossing between two populations of the same species. All individuals of a species share similar anatomical and morphological features.

The Monera Kingdom: Prokaryotic Life

The Monera kingdom is constituted by the vast majority of prokaryotes. Their cells are bacteria, tiny living things. They are the most abundant organisms and have spread throughout the biosphere. There are species adapted to live in all types of habitats: warm, cold, with oxygen, without oxygen, and so on.

Characteristics and Classification of Monera

Monera are broadly classified by shape:

• Cocci: Spherical (e.g., staphylococci, which can cause food poisoning).
• Bacilli: Elongated, rod-shaped.
• Vibrios: Curved or spiral-shaped.

They have a highly resistant cell wall. Some bacteria also have flagella that facilitate their movement in liquids.

Reproduction and Metabolism of Monera

Monera reproduce primarily by binary fission. When bacteria are in favorable environments for growth, they reproduce very quickly.

Their metabolism and type of nutrition are very varied. Based on their nutrition, they can be classified as:

• Autotrophs: They produce their own food through photosynthesizing or chemosynthesis.
• Heterotrophs: They obtain nutrients from other sources. They can be:
  • Saprophytic: If they live on dead organic matter.
  • Parasitic: If they live at the expense of other living beings.
  • Symbiotic: If they associate with other living beings for mutual benefit.

Domains within the Monera Kingdom

There are two primary domains within the Monera kingdom:

Eubacteria: True Bacteria

Eubacteria are the most numerous of the Monera. The majority are beneficial, including decomposers. Pathogens, which cause disease, represent only a small portion of eubacteria. Within this domain, there are successfully identified 9 groups, two of which are:

• Cyanobacteria: Photosynthetic bacteria, often called blue-green algae.
• Mycoplasmas: The smallest known free-living bacteria, lacking a cell wall.

Archaebacteria: Ancient Extremophiles

Archaebacteria are prokaryotes considered very primitive. They live in habitats with extreme conditions, both aquatic and terrestrial. They can withstand high temperatures, high salinity, and strongly acidic or very alkaline environments. They are classified as:

• Methanogens (Methane-producing): Living in the digestive tracts of herbivores and responsible for much of the methane in the atmosphere.
• Halophiles (Salt-loving): They live only in highly saline waters, giving them a pink tinge due to their pigments.
• Thermophilic Acidophiles: They live in environments with very high temperatures and high acidity.