LIFE PROCESSES IN ANIMALS 



273 



as it does so the animal moves, frequently leaving waste 

 products in its path. These are given off at any point 

 on the body. Amebas also breathe. Oxygen diffuses 



Fig. 130. An ameba giving off waste products. 



into the body and carbon dioxide is given off in the 



same manner. When an ameba becomes a certain size 



it divides into two nearly equal parts, and thus two 



smaller individuals are formed. These simple animals 



are also sensitive to certain 



agencies, stimuli, acting upon 



them. They are sensitive to 



some extent to contact, to 



heat, to chemical conditions 



of the water, to food, to light, 



and the like. 



In this simple animal we 

 find the following processes: 



1. It takes food into the body. 



2. It digests this food. 3. 

 It gives off waste products. 



4. It takes oxygen into the cell and carbon dioxide is 

 given off. 5. It moves. 6. It is sensitive. 7. It repro- 

 duces. From the simple organization of this animal 

 we may infer that all of these functions, at least, are 

 necessary for the life of any animal. 



Fig. 131. Four stages in the 

 division of an ameba. 



