Answer:
The correct answer is - parasite.
Explanation:
In the symbiotic relationship of where one of the symbiotic partner get benefited in the symbiosis and other partner harmed is known as the parasitism.
In this parasitism symbiotic relationship, the organism harmed called the host while the other partner that gets benefited from the parasitism is termed parasite.
 
        
             
        
        
        
It is a perfect example of a natural selection.
(I'm not sure if this is the exact answer that you are looking for.)
        
                    
             
        
        
        
Glycolysis is the first step whereas Krebs cycle is the second step of cellular respiration.
They both formed 2 molecules of ATP along with some carbon as a waste.