Waves are folds of water cause by the gravitational pull of the moon. 
When waves occur, it mixes the water and makes it to where there's less algae and gunk in the water, making it more inhabitable for sea life. 
 
        
             
        
        
        
The endocrine system is made of glands that secrete hormones. These hormones help regulate the organs and cells activity. The hormones among other things control your metabolism.
 
        
             
        
        
        
Answer:
A shark's skeleton is made of cartilage , a type of strong but flexible tissue .Most other fish are covered in smooth , flat scales . A shark is covered in sharp , toothlike scales called denticles . Most other fish have flaps over their gills.
Explanation:
I hope it's help yu and plz mark me brainliest........... plz plz plz
 
        
                    
             
        
        
        
I think calcium but i could be wrong