The main responsible for the delay among the atrial and
ventricular contractions is the action potential conduction velocity of the AV
node cells. If the atria and ventricles contract simultaneously, atria cannot
give any help in filling the ventricles, which is needed, especially in those
with stiff ventricles as in the elderly. Hence atria have to contract first and
then the ventricles.
 
        
             
        
        
        
 <span>In bacteria, DNA polymerase adds an incorrect base to a growing strand of DNA about once in every 100 000 bases added. The result is a mismatch such as the pairing of A with C. 
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Answer:
lysosomes
Explanation: 
Animal cells each have a centrosome and lysosomes, whereas plant cells do not. Plant cells have a cell wall, chloroplasts and other specialized plastids, and a large central vacuole, whereas animal cells do not.
 
        
             
        
        
        
Answer:
I believe this would be The Scientific Method
Explanation: