Because the stomach is lined by a mucous membrane (the gastric mucosa)
        
             
        
        
        
That waste product would be carbon dioxide.
        
             
        
        
        
"An example of mutualism in the rainforest is the pollination of the Durian tree by bats."
        
                    
             
        
        
        
Red foxes are omnivores. Their diet includes small animals such as  birds, squirrels, rabbits and mice, but also berries, grasses and insects such as crickets, caterpillars, grasshoppers and beetles. Red foxes are therefore primary as well as secondary consumers, and even apex predators. Their removal from an ecosystem would most likely reduce the predation pressure on small animals and insects, and may result in population explosions of these prey animals. This in turn may result in additional pressure on the ecosystem as these animals exceed the carrying capacity, and could lead to other plant and animal species within the food web being decimated. Basically, the balance of the ecosystem would be lost until a new equilibrium can be established.   
        
             
        
        
        
The answer your looking for is the insula. Hope this helps.