XXVIII. LIFE PROCESSES OF ANIMALS 



In our study of the animal kingdom we have seen that 

 certain processes, necessary to the hfe of the individual and 

 to the perpetuation of the species, go on in the body of 

 every animal. Since the hfe of the animal and the future 

 existence of its kind depend upon these processes, they have 

 been termed the life processes. Among the more important 

 are ingestion, digestion, secretion, excretion, respiration, 

 circulation, and reproduction. 



Ingestion. — The combined activities of procuring, mas- 

 ticating, and swallowing food may be termed ingestion. 

 Without food, the animal would soon die. Therefore, 

 every animal is provided with some means of obtaining it 

 and passing it to the organs of digestion. When the amoeba 

 touches a bit of food, the protoplasm of the body simply 

 incloses the particle, for this animal has no mouth or special 

 organs for ingesting food. The ciha of the Paramecium 

 and vorticella create currents of water that bring food into 

 the mouth. Food is brought to the sponges by the currents 

 of water flowing through the body. The hydra, sea anemone, 

 and coral polyps gather food and pass it into the mouth 

 with the tentacles. The tapeworm absorbs its food through 

 the skin, but the earthworm swallows quantities of soil 

 from which the food particles are extracted. Insects have 

 biting and sucking mouth parts for obtaining their food. 

 Fish have jaws armed with teeth, while toads collect their 

 food with the tongue and swallow it whole. The snakes 



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