Answer:
1:1
Explanation:
What is the concentration of H+ ions at a pH = 7?
⇒ 0.0000001 mol/L  
What is the concentration of OH– ions at a pH = 7?
⇒ 0.0000001 mol/L  
What is the ratio of H+ ions to OH– ions at a pH = 7?  
1 :1
 
        
                    
             
        
        
        
"Prophase I" is the stage of meiosis that synapsis and the formation of tetrads occur.
        
             
        
        
        
Remember the definition of Osmosis; Water travels through a semipermeable membrane to an area of higher to lower concentration. Since the concentration of a solute is higher outside, we can make the assumption that water concentration is lower, and so the cell is going to release water to balance out and equalize the solution and it's surroundings. 
        
             
        
        
        
Answer:
Hi there!
Your answer is:
It is very important for the cell membrane to be <em>semi-permeable</em> because the ability to pick and choose what comes in and out of the cell keeps the cell safe! The membrane can choose to block out nasty germs and can also choose to get rid of internal waste. 
An example of when this is important is in this scenario:
Let's say the cells are in a really salty solution. Naturally, salt will want to pull the water out of the cell. If the membrane <u>wasn't</u><u> </u> semi permeable, the water would listen to the salt and leave the cell. This would cause cell death. <u>BECAU</u><u>SE</u> the membrane is semi permeable, they can choose <em>not</em> to give the salt any water, keeping them alive
Hope this helps
 
        
             
        
        
        
A halite crystal belongs to the cubic crystal system. The other five crystal systems are monoclinic, triclinic, orthorhombic, tetragonal, and <span>hexagonal.
The cubic crystal system is characterised by</span> <span>the way the atoms in the mineral are arranged in the three </span><span>dimensional</span><span> shape of a </span>cube. The halite crystal has this shape. Attached is an image of it.