Final answer:
The kingdom Bacteria is made up of single-celled prokaryotic organisms without a nucleus, known as the domain Bacteria, formerly classified under kingdom Monera. Though similar to the domain Archaea, they differ notably in cell wall structure and habitat preferences, including Archaea's ability to inhabit extreme environments.
Step-by-step explanation:
The kingdom Bacteria is composed solely of the domain Bacteria, which was formerly categorized under the kingdom Monera in older classification systems. The domain Archaea and the domain Bacteria both consist of single-celled prokaryotic organisms, which means their cells do not contain a nucleus or membrane-bound organelles. While they may share some similarities, such as the ability to reproduce asexually and having cell walls, there are marked differences between the two domains. For instance, bacterial cell walls contain the polysaccharide peptidoglycan. Additionally, many Archaea are known to thrive in extreme environments such as hot springs and salt flats—conditions where the bacteria from the Bacteria domain generally do not live.
Understanding the distinctions and characteristics of these domains is crucial, especially when one considers that prokaryotes were the first life forms to emerge on Earth and are found in almost every environment imaginable, from the harshest of habitats to the most common, like our own systems. These extensive varieties encompass the diversity of life within the domains Archaea and Bacteria. In the current classification system, the highest level of organization is the domain, which includes the Eukarya, Archaea, and Bacteria, with Prokaryota being an informal term for organisms in the domains Archaea and Bacteria without nuclei.