Definition

Proper noun A major taxonomic group in biological classification, encompassing all prokaryotic organisms. This kingdom includes bacteria, cyanobacteria (blue-green algae), and various primitive pathogens. It is characterized by organisms whose cells lack a membrane-bound nucleus and other complex organelles.

Usage Notes

• This term is primarily used in the context of scientific taxonomy and biology.
• It represents one of the five kingdoms in a traditional biological classification system (the Five-Kingdom system proposed by Robert Whittaker).
• Due to significant genetic differences discovered later, the organisms within this kingdom are now more commonly classified into two separate domains: Bacteria and Archaea, under the three-domain system of life.

Examples

• In the five-kingdom system, Kingdom Prokaryotae includes all single-celled organisms without a true nucleus.
• Kingdom Prokaryotae was once used to group together both eubacteria and archaebacteria.
• The study of organisms in Kingdom Prokaryotae is crucial for understanding fundamental life processes and ecology.

Advanced Usage

• Informal Major Divisions: As noted in the reference, there is a lack of consensus on formal phyla within this broad group. Therefore, informal names based on shape, staining properties, or metabolism (e.g., cocci, bacilli, Gram-negative bacteria, cyanobacteria) are often used to describe its major divisions.

Variants and Related Words

• Monera (n): A synonymous term for Kingdom Prokaryotae used in many classification systems.
• Prokaryote (n): An individual organism belonging to Kingdom Prokaryotae; any cell or organism lacking a distinct nucleus.
• Prokaryotic (adj): Of or relating to prokaryotes; describing the cellular structure of organisms in this kingdom.

Synonyms

• Monera
• Prokaryotes (as a collective group)

Related Concepts (Not Synonyms)

• Bacteria: The domain containing the majority of organisms formerly placed in Kingdom Prokaryotae.
• Archaea: The domain comprising primitive, often extremophile prokaryotes once included in Kingdom Prokaryotae.
• Eukaryote / Eukarya: Organisms with cells containing a nucleus, which are part of Kingdom Prokaryotae.

Noun

1. prokaryotic bacteria and blue-green algae and various primitive pathogens; because of lack of consensus on how to divide the organisms into phyla informal names are used for the major divisions