The Phylum Zoomastigina contains organisms, such as trichonympha and trypanosome, which have flagellum and belong to the larger class of protozoa. This phylum includes many different organisms, but all have the distinct feature of having flagellum, which are long, whip-like extensions in their rears that look and function like tails. Organisms in this phylum are eukaryotes; they lack chloroplasts and may live in many different environments, including the surface of the Earth, below ground, in the atmosphere and in water.
Flagellates and trypanosomes are among the most common organisms in the Phylum Zoomastigina. Flagellates are unicellular and eukaryotic organisms. As with other species in the phylum, flagellates have flagella, but these extensions develop as flagellates enter adulthood. Flagellates are among the oldest and most abundant organisms on Earth; they are primitive in biological composition and outward appearance. They are abundant and live in many areas, including the digestive tracts of other organisms, including mammals and even humans. Flagellates are heterotrophic and may reproduce sexually or asexually. Trypanosomes are similar to flagellates in appearance, but they live almost exclusively in the digestive systems of mice and rats. These organisms are among the smallest zoomastigina species, and are generally benign, unlike flagellates and other zoomastiginas, which may carry and produce disease and infection.