When a protist is ready to eat, it will wrap its cell wall and cell membrane around its prey,
which is usually bacteria. In doing so, it creates a food vacuole or a sort of “food storage
compartment.” Next the protist produces toxins which paralyze its prospective dinner. Once
paralyzed, the food material simply moves by force of gravity through the vacuole and into
the cytoplasm of the hungry protist. Other protists are parasitic, and absorb nutrients meant
for their host, harming the host in the process.
Animal-like Protists
Animal-like protists are called protozoa. Protozoaare unicellular eukaryotes that share
certain traits with organisms in the animal kingdom. Those traits are mobility and het-
erotrophy. Animal-like protists areheterotrophswhich mean they get their carbon from
outside sources—in other words, they eat organic materials. Animal-like protists are very
tiny measuring only about 0.01–0.5mm. Animal like protists include the zooflagellates, cili-
ates, and the sporozoans (Figure9.3).
Figure 9.3: Euglena are animal-like protists. Over 1000 species of Euglena exist and are
used in industry in the treatment of sewage. ( 5 )
Although most protists obtain nutrition through pinocytosis, some protists literally “eat
with their tails”. The tail of a protist is a flagellum and these protists are calledflagellates.
Flagellates acquire oxygen and nitrogen by constantly whipping the flagellum back and forth
in a process of filter-feeding. The whipping of the flagellum creates a current that brings
food into the protist.
Aflagellum(plural: flagella), is a tail-like structure that projects from the cell body of
certain prokaryotic and eukaryotic cells, and it usually functions in helping the cell move.