Euglena is a/an ______ organism.

Euglena is a single-celled organism belonging to the phylum Euglenozoa within the group of protists. Like other protozoans and many microorganisms, it exists as an individual cell that performs all life functions within one cellular unit. Multicellular organisms consist of many specialized cells working together, acellular refers to entities without cells (like viruses), and syncytial describes multinucleate cytoplasm without cell boundaries - none of which describe Euglena.