Science williams Crossword
                
                
                
                
                
                
                
                
                
                
                
                
 
 
Down: 1) air sacs within the lungs where gases are exchanged between the lungs and the blood2) 4) a form of a trait carried by a gene Across: 1) an inherited trait that increases an organism's chance os survival3) any nonliving part of an ecosystem4) a form of immunity that develops from exposure to a pathogen
 

 

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