Answer: Mutualism is a relationship of two organisms wherein both organisms benefit from each other. ... Commensalism is a relationship of two organisms wherein one organism benefit from the other with neither harm nor benefit to the other
        
             
        
        
        
Answer: positive sodium ions
Explanation:
This relates to the Action Potential which is what a nerve cell goes through when it needs to send information down the nerve cell to another cell and so on till it gets to the destination of the message. 
The information is transmitted when the segments of the axon fire and when they do, positive sodium ions come in from outside the cell to the inside thereby making the inside positive. The previous segment would return to a resting potential when potassium ions which are negative, rush into the cell. 
 
        
             
        
        
        
Answer:
There were 1.2 billion persons in the year 1850
Explanation:
 
        
                    
             
        
        
        
I might be wrong but soil?
        
             
        
        
        
Because if you come across something surprising, it's best to know how and why that happened