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Proteins are responsible for the <u>mass </u>and <u>fat </u>of much of our bodies (and other organisms). The instructions for making protein are encoded in <u>DNA</u>. These genes provide the sequence of building blocks known as <u>nucleotides</u>. This string of amino acids then folds into different shapes. The structure of proteins determines what a <u>molecule </u>can do. Proteins contain carbon, hydrogen, oxygen, and nitrogen. 
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<em>Kindly pardon me: I ain't so sure of the first two answers.</em>
 
        
             
        
        
        
Answer:
Sharks, in their basal form have been on Earth for hundreds of millions of years.  They were the first to develop a stream-like, torpedo shaped body and created a niche for themselves. Their aerodynamic body shape has evolved to allow for efficient and dynamic movement in water. Having a cartilage instead of bones allowed them to grow large and still be relatively light and buoyant . After they've evolved flexible, protruding jaws, there wasn't much to change. They were able to adapt and exploit all the water habitats as the world was changing.
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