The general theory is that mitochondria and chloroplasts began initially as separate cells that were "eaten" by larger cells, but not digested and simply passed on due to their advantages.<span />
        
             
        
        
        
Answer:
Connective Tissues
Explanation:
According to my research on studies conducted by various medical professions, I can say that based on the information provided within the question this scientist is most likely looking at Connective Tissues. These are tissues in which material secreted by the cells is fills up the spaces between the cells, thus connecting or binding otherwise separate tissues or organs. Which is what the scientist seems to be describing.
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Answer:
They are called  decomposers.
Explanation:
 
        
                    
             
        
        
        
Well considering the lack of information given, most logically we can conclude it’s the peripheral nervous system.