Answer:
Changes that cannot be reversed are called irreversible changes
Example: if you cook an egg or if something goes bad. these changes can not be reversed.  
 
        
             
        
        
        
Answer: The fertilized ovum, now called a zygote, is ready for the first mitotic cell division.
 
        
             
        
        
        
Answer:
nervous, skeletal, and muscular
Explanation:
 
        
             
        
        
        
Would this be speciation?