TWO PATTERNS OF LIFE 



5 



armor it was able to exist under many adverse conditions of 

 dessication and physical contacts which would have been fatal 

 to naked protoplasm. By far the majority of organisms today 

 consist of protoplasm thus organized into units or cells. Not only 

 are plants and animals alike in being made up of protoplasm, 

 but both have the protoplasm organized into cellular units. 

 The success of this step upward in the evolution of life is attested 

 by the fact that there still are many thousands of microscopic 



BACTERIA 



PROTOZOA 



Fig. 1 . — A drop of water from a stagnant pool reveals a microscopic world of 

 unicellular organisms including bacteria, protozoa and algae. 



plants and animals which live in the unicellular condition, the 

 whole body being restricted to the dimensions of a single cell. 

 Such are the Protozoa in the animal kingdom, of which familiar 

 representatives are the simple Amoeba or the more complex 

 Paramecium, both carrying on all the activities typical of an 

 animal within the limits of a single cell. Plant species of this 

 simple type of body organization are also common. A drop of 

 water from a stagnant pool (fig. 1 ) reveals a microscopic world 

 of Protozoa and unicellular plants; the colorless rods and spheres 

 of bacteria, the boat-shaped cells of yellowish diatoms, and 



