This exercise includes example protozoa from the three major protozoa phyla.  Protozoans are eukaryotic unicellular organisms.  They are important to us ecologically as producers (autotrophs such as Euglena), consumers of small organisms such as bacteria or other protozoa (Paramecium or Stentor), beneficial symbionts (such as Trichonympha), or disease-causing parasites (such as Plasmodium).