- Flagellates are distinguished by the presence of one or more flagella.
- Classically, the group has included many autotrophic groups (phytoflagellates), such as chrysomonads, euglenids, and the volvocids. They possess chlorophyll plus other pigm ents and store such food materials as oils, fats, and starches (other than glycogen). These groups are more properly assigned to the various algal phyla.
- The remaining heterotrophs (zooflagellates) are a small, heterogeneous assemblage. A few are free living, but most are parasitic, commensal, or mutualistic in other animals.
- Flagella (and cilia) are composed of microtubules surrounded by the plasma membrane. The arrangement of m icrotubules in which nine pairs (doublets) surround two central microtubules is with few exceptions characteristic of flagella and cilia in all eukaryote organism s. Movement of the organelle is thought to result from the sliding ofated with the microtubules relative to each other. Each flagellum (or cilium] arises from a basal body, or kinetosome.
- Flagella commonly beat by undulation in two planes. The beat pushes or pulls the flagellate, and the path of movement depends on the point of flagellum attachment and the combined action, when there is more than one flagellum.