Answer:
Because it helps the planet
Explanation:
Trust me
 
        
             
        
        
        
Once entering the atmosphere the heated up water vapor (that's the process of evaporation) cools back down (the atmosphere is cooler than the Earth you see). it makes clouds Their it will condense until it's heavy enough to fall to Earth as precipitation!  
        
                    
             
        
        
        
Answer:
Sheep carrying out respiration
Explanation:
Because the sheep is exhaling carbon dioxide into the air
 
        
                    
             
        
        
        
Answer: Mitochondria 
Explanation:
Mitochondria are rod-shaped organelles bounded by a double membrane in which the inner membrane is folded and filled with matrix. Mitochondria is present in both plant and animal cells, and serves as the power house where respiration occur and energy is released from the oxidation of simple sugar.
 
        
             
        
        
        
Mainly to make life easier.
if one layer changes than scientists don't need to change all of their data.
it also helps keep organized.
hope this helped
ebs02
:)