Answer:
(See Attached Punnet Sq)
Explanation:
There are two genes here represented different alleles (Yy & Ss). According to Mendelian law, the principle of independent assortment applies to mean each allele has equal chances of ending up in a gamete. Therefore each gamete can have either allele of the two genes as shown in the punnet square. The combinations of the offspring are therefore numerous.
 
        
             
        
        
        
The answer is environmental stress
        
             
        
        
        
Oxygen Depleting can cause Warm water. During summer, The upper layer of the water is lighter therefore it does not mix with the cooler water below. Which soon becomes stagnant. (Oxygen becomes depleted and toxic compounds may produce). 
That is one of them. I hope it helps. I'm not so good when it comes to this type of science. But if you ever need help with Anatomy Or anything similar to that. I will gladly help.