Answer
cutting or incision 
for example: gastrotomy means a surgical incision to the stomach 
 
        
                    
             
        
        
        
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The bottom of the sea is lined with calcium carbonate, which comes from the shells of zooplankton that have died and sunk to the ocean floor. ... As a result, according to a study published recently in PNAS, parts of the seafloor are disintegrating.
        
             
        
        
        
Answer:
The population is people who buy mystery novels at that specific book store.