If producers were removed from an ecosystem, it would fall apart. Producers are the organisms at the bottom of the food chain, which produce glucose and nutrients for consumers. If producers were removed from an ecosystem, the consumers would have no nutrients and die, causing their predators to die, and so on.
        
             
        
        
        
C. The brain sends messages to the spinal cord
        
             
        
        
        
Answer:
Cellular Respiration: a process able to extract a large amount of energy from food molecules.  In eukaryotic cells oxygen is a required component. This metabolic process is the main reason that animals have elaborate gas exchange organs such as lungs, gills and other systems. The goal of these systems is, of course, to get access to oxygen and to get rid of carbon dioxide.
Explanation: