Answer:
By the process of cellular differentiation which consists of physical and functional changes of the cell used by processes at the genetic level. The expression of these in each type of cell is different. That is to say that the type of cell follows at a time of development there is differential activation of some genes and repression of others
 
        
             
        
        
        
Answer:
An explosion of a star= Supernova 
The dense remains of a star= Neutron star 
A large mass of gas and dust= Nebula 
Explanation:
 
        
                    
             
        
        
        
Answer:
homologous structure
Explanation:
those organs which have the same basic structure but have different functions are known as homologous organs/structures.
 
        
                    
             
        
        
        
Answer:
The reduction of friction between the parietal and visceral surfaces of an internal cavity is the function of serous fluid.
Explanation:
Between the parietal layer and visceral layer of an internal cavity there is serous fluid that reduces the friction between these two surfaces and allows an easier movement of the parietal and visceral layers. The serous fluid is produced by serous glands that are in the parietal and visceral membrane.