Although the term "algae" is no longer used in classification, it is still a useful term to describe aquatic photosynthetic organisms with little tissue differentiation. Chlamydomonas is a single-celled protist; Spirogyra and Oedogonium are filamentous. Fucus is a macroscopic organism, placed in the plant kingdom in some textbooks.
View movies of Euglena gracilis on the right side of the page by clicking on the still images.
What characteristics do these cells have that are like plants?
Are like animals?
Note that these cells divide by mitosis, and therefore asexually. Does Euglena have a sexual cycle?