Circulatory and Respiratory systems working together to provide body with oxygen. 
 
        
                    
             
        
        
        
Answer:
By exercising, it increases blood flow towards the muscles and digestive tract. This can help move food through the stomach, or digestive tract.  
 
        
             
        
        
        
Answer: PCR allows us to target and amplify one specific segment of DNA that is a few hundred base pairs in length out a complete genome of over 3 billion base pairs.
Explanation:
 
        
             
        
        
        
Answer:
B The version of the trait that is expressed over other alleles for the same trait I believe
 
        
                    
             
        
        
        
Answer:
Explanation: investment in offspring by the parent that increases the offspring's chances of surviving and hence reproductive success at the expense of the parent's ability to invest in other offspring.