Answer:
Energy transferred during a chemical reaction. ... In an exothermic reaction, the potential energy of the system goes down, and heat is given out. In an endothermic reaction, the potential energy of the system goes up, and heat is taken in.
Explanation:
 
        
             
        
        
        
160lbs also WHO IN THEIR RIGHT MIND WOULD ASK SUCH A QUESTION!?!?!?
        
             
        
        
        
Introduced species
Ecosystems are complex systems that are in dynamic equilibrium with constant interactions between their parts.
When a new species is introduced, new interactions will occur, generating new components of the system and also competing with the previous interactions between the species already present in the system, which normally ends up generating an imbalance in the ecosystem mentioned, i.e a disruption in it. 
 
        
             
        
        
        
Answer:
The sperm and egg have 1/2 the amount because when the sperm fertilizes the egg, it equals out to the regular amount of chromosomes. That is why we have half chromosomes from our dad and half chromosomes from our mom, equaling out to normal amount of chromosomes.
 
        
                    
             
        
        
        
Pollution from a near by city is your answer ;D