This organism consists of a single cell with several flagella. Is it a prokaryote, such as a bacterium? Actually, it’s larger than a prokaryotic cell, and it also has a nucleus. Therefore, this organism belongs to the domain Eukarya, the domain that includes humans. This particular eukaryote is one of the smallest, simplest organisms in the domain, called a protist. It’s scientific name is Giardia lamblia. As a human parasite, it can make us sick.
In this chapter, you’ll read more about protists like Giardia lamblia. You’ll discover that protists have a wide diversity of traits and ways of life. And only some of them make us sick.