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Many protists take the form of single-celled flagellates. Flagella are generally used for propulsion. They may also be used to create a current that brings in food. In most such organisms, one or more flagella are located at or near the anterior of the cell (e.g., Euglena). Often there is one directed forwards and one trailing behind.
Archaeal flagella are superficially similar to bacterial flagella in that it also has a rotary motor, but are different in many details and considered non-homologous. [ 18 ] [ 19 ] [ 20 ] Eukaryotic flagella—those of animal, plant, and protist cells—are complex cellular projections that lash back and forth.
Flagellates typically have a small number of long flagella distributed along the bodies, and they actuate them to generate thrust. The set of observed movement sequences includes planar undulatory waves and traveling helical waves, either from the base to the tip, or in the opposite direction.
Kinetoplastida (or Kinetoplastea, as a class) is a group of flagellated protists belonging to the phylum Euglenozoa, [3] [4] and characterised by the presence of a distinctive organelle called the kinetoplast (hence the name), a granule containing a large mass of DNA.
Breviatea, a small class [a] related to animals, fungi and amoebozoans, is composed of anaerobic amoeboflagellates with two flagella. [13] [14] Percolozoa contains amoeboflagellates with lobose pseudopods, but are differentiated by their flat mitochondrial cristae, not tubular as in Amoebozoa.
Its cell typically measures between 3 and 10 μm and it has a volume of around 20 μm 3. [2] It is colorless and has two unequally sized flagella. The smooth flagellum, angled posteriorly, is shorter, and attaches to substrates in non-motile cells, but trails behind in motile cells. The hairy flagellum points forward in an arc in sessile cells.
These protists are equipped with one or more whip-like appendages called cilia, undulipodia or eukaryotic flagella, [b] which enable them to swim or glide freely through the environment. Flagellates are found in all lineages, reflecting that the common ancestor of all living eukaryotes was a flagellate.
The prasinophytes are a group of unicellular green algae. [4] Prasinophytes mainly include marine planktonic species, as well as some freshwater representatives. [4] [5] The prasinophytes are morphologically diverse, including flagellates with one to eight flagella and non-motile (coccoid) unicells.