Theory:

Various life processes essential to sustain life:
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The Life Processes
 
Chavan_R_L_&_Khandagale_V_S-Human_Digestive_System-Concept_Map.png
Digestive system in Humans
 
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Respiratory & Circulatory system in Humans
 
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Excretion in Humans
Reference:
https://upload.wikimedia.org/wikipedia/commons/5/57/Chavan_R_L_%26_Khandagale_V_S-Human_Digestive_System-Concept_Map.png
https://www.flickr.com/photos/121935927@N06/13537080705/in/photostream/
https://cmapspublic3.ihmc.us/rid%3D1178479838751_993950325_30367/excretory%2520system.cmap%3Frid%3D1178479838751_993950325_30367%26partName%3Dhtmljpeg