CHAPTER II 



Protozoa 



The Protozoa (Gr. protos, first; zoon, animal) are the simplest 

 living animals and some of them resemble plants. Primitive and 

 mostly microscopic though they are, the Protozoa are complete 

 organisms in a single cell, carrying on the physiological processes of 

 higher forms. A protozoan may be ameboid, flagellated, or ciliated, 

 depending on its organs of locomotion. 



Classification 



Class 1. Sarcodina (Gr. sarx, flesh) move by false feet or pseudo- 

 podia. 



Class 2. Mastigophora (Gr. ?nasfix, whip; and phero, bear) move by 

 flagella. 



Class 3. Infusoria (Lat. in/usus, crowd In) move by cilia, and are 

 also called Ciliata. 



Class 4. Sporozoa (Gr. spo?'a, seed; and zoon, animal). No loco- 

 motor organs in adult stage. 



Characteristics 



1. Morphologically the simplest ones are equal to isolated epi- 



thelium. 



2. Physiologically they are equal to the whole group of cells making 



up the human body. Protozoa are complete unicellular 

 organisms and many have a brief multicellular phase. 



3. Functionally they epitomize life processes. 



4. Theoretically they are generalized cells. 



5. Of practical economic importance, they cause many diseases. 



6. As soil organisms protozoa are of doubtful importance. 



Protozoa were first discovered by Leeuwenhoek in rain water. 

 Misconceptions arose because of the insufficient magnification 

 possible. O. F. Mueller (1786) made the first classification. He 

 classified 350 species, 150 of which are still regarded as valid. He 



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