Prokaryotes – Incredibly Diverse
First, I will talk about their habitats. They live in many different habitats; some live in extremely salty conditions (9% for one), and many live in extreme heat, such as black smokers (more detail here), and geothermal vents (more detail here). They also create biofilms on your teeth (plaque) and on medical equipment. Some can only survive in areas with no oxygen, and others require oxygen to live. Others live on animals and people, helping the host through symbiosis to carry out its body functions, such as digestion.
Prokaryotes can obtain nutrition multiple ways. First, it could wander around and eat dead cells or even prey on live ones, but this method is in the minority. The most common method is the creation of usable energy through photosynthesis or the use of other minerals, like sulfur, to create usable energy for the prokaryote.
I’m not even scratching the surface; there is so much info and data out there on prokaryotes and all forms of cells. Without them, we would probably not be around today, as we depend so much upon them for food and the ability to get food from the environment.