Prokaryotic organisms are primarily found in two kingdoms: Archaea and Bacteria.
Archaea are single-celled microorganisms that are similar to bacteria in size and simplicity of structure but are genetically and biochemically distinct. They often thrive in extreme environments such as hot springs, salt lakes, and deep-sea hydrothermal vents.
Bacteria are also single-celled organisms that are found in nearly every habitat on Earth. They play crucial roles in various ecological processes, including decomposition, nitrogen fixation, and the production of oxygen through photosynthesis.
Both Archaea and Bacteria lack a nucleus and membrane-bound organelles, which are characteristics of eukaryotic cells. Instead, their genetic material is located in a region called the nucleoid.