Euglena are unique in that we cannot classify them in only one group of protists...why?
Protists are an interesting group in that they serve as kind of a catch-all classification for organisms that don't fit into other kingdoms (animal, plant, bacteria, or fungi). They are eukaryotes but are either unicellular or multicellular without any higher organization. Euglena are classified as protists but there is some difficulty in classifying them exactly due to the fact that they are both autotrophs and heterotrophs. In other words, they can both produce their own food and also consume outside food. They contain chloroplasts for sugar formation and enzymes for food breakdown.