The above image shows bacteria dyed with a fluorescent color. They look just like little cells. Well, that's exactly what they are.
Bacteria are prokaryotic organisms. About 3.5 billion years ago, long before the first plants, people, or other animals appeared, prokaryotes were the first life forms on Earth. For at least a billion years, prokaryotes ruled the Earth as the only existing organisms.
What do you think of when you think of bacteria? Germs? Diseases? Bacteria can be harmful, but they can also help you. How do you think bacteria can help humans and other organisms?
Did you know that bacteria are not the only type of prokaryote? There is another type, called archaea, which we will explore in addition to the questions asked above.
Jed Fuhrman. commons.wikimedia.org/wiki/File:Seawater_small_life.png. CC BY 2.5.