Protozoan are unicellular
organisms that live in moist environments (including soil). Most
protozoans are free-living, meaning they do not require a
host to survive. A small percentage of
protozoans cause human disease. Most
protozoans form
cysts in adverse conditions.
Amoebas
- Amoebas are large protozoans that move by pseudopods.
- Example: Entamoeba histolytica causes amoebic disentery (intestinal disease)
Flagellates
- Flagellates move using one or more flagella.
- Examples: Trichomonas vaginalis (sexually transmitted disease) and Giardia lamblia (causes diarrhea)
Ciliates
- Ciliates move by using cilia.
- Example: Balantidium coli (intestinal disease)
Sporozoans
- These very small protozoans can enter the host cell. They also often need two hosts to complete their life cycle.
- Example: The Plasmodium sporozoan causes malaria. Its primary host is mosquitoes, who inject the immature protozoans into humans to complete its life cycle.
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1 - Anatomy and Physiology Basics