Scientists assign Euglena to the Kingdom Protista, although these unique organisms share characteristics of plants and animals. The complex physical and biological structures of Euglena keep them from meeting all the qualification criteria of most kingdoms, but they most closely resemble protists. The Kingdom Protista contains other microorganisms like amoebas and paramecium, making it the most suitable classification for Euglena.
The Euglena family contains over 800 species of organisms. These organisms form from single cells and move through water using flagella. They thrive in aquatic environments around the world, residing primarily in still freshwater bodies. Euglena possess the unique ability of producing their own food like plants, and consuming food like animals. These feeding habits prevent placement in either a true plant or animal kingdom. As autotrophs, Euglena perform photosynthesis like other plants. They absorb sunlight, which then transfers into energy and fuel. Euglena typically appear in various shades of green; the green color derives from ingesting green algae, their primary food source. Lack of adequate sunlight prompts Euglenas' transition to heterotroph mode. As heterotrophic feeders, they surround and ingest particles of food. In addition to algae, Euglena feed on other microbes. A bright red spot on the organisms' top gives a distinct appearance and helps Euglena find sunlight.