VITAL ANIMAL LIFE PROCESSES 



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Groups of organs are combined to form organ systems — the stomach, 

 small intestine, large intestine, liver, and pancreas are organs which 

 aid in digestion and therefore we say they belong to the digestive sys- 

 tem. 



Organ Systems 



The simpler animals carry on their vital life processes without any 

 specialized organ systems ; but as animals become larger and more 

 complex in their morphology, the various organ systems are developed 





Cell 



(Organ system) 

 digestive system 



Tissue 

 (columnar 

 epithelium) 



Oraan 

 (colon) 



Fig. 5.2. Diagram to show how cells make tissues, tissues make organs, and organs 

 make organ systems. This is the digestive system of man. 



and perform the necessary life functions. We will list the organ sys- 

 tems which are found in the highest forms of animals, the vertebrates. 

 In less complex animals, some of the systems may be present and 

 others lacking. 



Digestive System. This system takes care of ingestion, digestion, 

 absorption, and egestion. 



Respiratory System. This system functions to absorb oxygen 

 from the environment (air or water) and gives off carbon dioxide. 



Excretory System. This system removes and excretes the wastes 

 of metabolism. 



