* Bacteria: This is the most diverse and abundant group of prokaryotes. They are found in nearly every environment on Earth, including soil, water, and the human body. Bacteria can be beneficial, such as those involved in nitrogen fixation and food production, or harmful, such as those that cause disease.

* Archaea: These prokaryotes are often found in extreme environments, such as hot springs, salt lakes, and deep-sea vents. They have unique biochemical features that distinguish them from bacteria, including different cell wall structures and membrane lipids. Some archaea play important roles in the environment, such as in methane production.