In humans, the yolk sac is the
site of origin for blood cells and primordial germ cells. The human yolk sac is
a membrane located outside the embryo and it is connected by a tube through the
umbilical opening to the embryo's midgut. The yolk sac serves as an early site
for the formation of blood and in time, is incorporated into the primitive gut
of the embryo.
 
        
             
        
        
        
So children<span> look like combinations of </span>their parents<span> because they are. Each </span>parent<span>gives half of </span>their<span> genetic material to </span>their children<span>. The combination makes a unique combination of </span>their parents<span> genes. The scientific study of how </span>traits<span> are passed from </span>parents<span> to </span>children<span> is called genetics. 
sry for the long answer</span>
        
             
        
        
        
On sooory I send u answer in msg
        
                    
             
        
        
        
The core, or middle, of the Sun is the hottest part. Hot gasses bubble up from the core to the surface of the Sun. When the gasses burn, heat and light are produced.
 
        
                    
             
        
        
        
An organism can "make a living" and survive in its niche.