Protozoa: a now obsolete term that referred to colorless protists and included flagellates, ciliates, amoebae and sporozoa. The protozoa were all thought to be single celled eukaryotes. The concept was popular for much of the 20th century, but it has become clear that some are relatives of animals and fungi, others have closer relationships with algae than with other protozoa, and that protozoa are not closely related. The term has largely fallen into disuse.

protozoa (protozoa (unspecified)) is prey of:
Crustacea
Entomostraca
Rotifera
Tardigrada
Nematoda
Oligochaeta
zooplankton
Actinopterygii
Polychaeta
Synchaeta
Polyarthra
Conochilus
Daphnia
Bosmina
Eudiaptomus
Mysidacea
Ostracoda
Euphausiacea
Hyperiidea
Cyclopoida
Calanoida
Chaetognatha
Tripteroides
Culex
Uranotaenia
Hydropsyche
Salmo salar
Phoxinus phoxinus

Based on studies in:
USA: California (Estuarine, Intertidal, Littoral)
Norway: Spitsbergen (Coastal)
New Zealand (Grassland)
Finland (Lake or pond, Pelagic)
South Africa (Desert or dune)
Russia (Lake or pond)
Pacific (Marine, Tropical)
Malaysia, W. Malaysia (Plant substrate)
Wales, Dee River (River)

This list may not be complete but is based on published studies.

protozoa (protozoa (unspecified)) preys on:
primary producers
detritus
algae
bacteria
phytoplankton
bacterioplankton
allochthonous organic matter
Insecta
fungi

Based on studies in:
USA: California (Estuarine, Intertidal, Littoral)
South Africa (Desert or dune)
Pacific (Marine, Tropical)
Malaysia, W. Malaysia (Plant substrate)
USA: Florida, Everglades (Estuarine)
Norway: Spitsbergen (Coastal)
New Zealand (Grassland)
Russia (Lake or pond)
Finland (Lake or pond, Pelagic)
unknown (Soil)

This list may not be complete but is based on published studies.

In Great Britain and/or Ireland:
Foodplant / feeds on
Rhizophydium gibbosum feeds on cyst of Protozoa

Cellulose digested for fuel: protozoans
 

Mixotricha protozoans digests cellulose for termite metabolism.

   
  "Termites harbor in their digestive system protozoa called mixotrichs that are critical to their ability to get energy by digesting cellulose." (Vogel 1998:29)
  Learn more about this functional adaptation.

Microscopic oars move organism: protozoan
 

Bundles of microtubules projecting from the microscopic Sticholonche zanclea move the protozoans along through a rowing motion.

   
  "At least one odd actinopod, heliozoan protozoan, Sticholonche, rows along with oars made of bundles of microtubules that emerge from the nuclear membrane through microfibrillar oarlocks. These form the central axes of external cytoplasmic protrusions--oars of a sort (Cachon and Cachon 1978; Margulis and Schwartz 1998)." (Vogel 2003:450)
  Learn more about this functional adaptation.