1. Bacteria: These are single-celled organisms that are incredibly diverse and abundant, found in nearly every environment on Earth.
2. Archaea: These are also single-celled organisms, often found in extreme environments like hot springs, salt lakes, and even the human gut. They are more closely related to eukaryotes (like humans) than bacteria, despite their prokaryotic structure.
So, while there are only two *kinds* of organisms with prokaryotic cells, there are countless *species* within those two categories. It's estimated that there are millions of different species of bacteria and archaea, making them incredibly diverse!
