Some individuals are more likely to survive and reproduce than others because they are fit and easily adapting. This idea is called 'survival of the fittest'.
        
             
        
        
        
Theories are educated guests that are tested by experiments
        
             
        
        
        
When a predator goes extinct, all of its prey are released from that predation pressure, and they may have big impacts on ecosystems.” ... “If there are too many deer, for example, they can really change the ecosystem because they can destroy forests, and they also carry disease,” Baldwin said.
        
             
        
        
        
C, because DNA is the smallest one
        
                    
             
        
        
        
Answer:
1.message or impulse sent through the nervous system
2.body or lymph performes the action. 
3.muscle contract 
4.message received at muscle fibers 
5.brain decides the action.