Caption: Protista (Protozoa)
Text: Protozoa are unicellular eukaryotes such as the amoeba and paramecium. Because protozoa do not have cell walls, they are capable of a variety of rapid and flexible movements. Protozoa can be acquired through contaminated food or water or by the bite of an infected arthropod such as a mosquito (e.g., malaria). Diarrheal disease in the United States can be caused by two common protozoan parasites, Giardia lamblia and Cryptosporidium parvum.