Amphibians have three heart chamber and they lay eggs so
                       AMPHIBIAN
        
                    
             
        
        
        
Answer:
cumulative dilution = 0.000001
Explanation:
A serial dilution is a stepwise kind of dilution repeated a certain number of times, in which the concentration reduces exponentially each time.
The cumulative dilution is the final dilution gotten depending on the number of times dilution has been done and the dilution factor. The formula is given as:
Cumulative dilution = (F)ⁿ
where: 
F = dilution factor = 0.1
n = number of serial dilutions = 6
∴ cumulative dilution = (0.1)⁶ = 0.000001
 
        
             
        
        
        
Microorganisms that are involved in the nitrogen cycle are able to break the triple of elemental nitrogen using special enzymes that they have developed and make ammonium. Other organisms like plants are unable to break the triple bond and therefore rely on these microorganisms so that they can absorb the ammonia