Answer and Explanation: The excretory system helps the respiratory system by getting rid of carbon dioxide. The respiratory system helps the excretory system by getting rid of CO2 from the body. They both need each other and if one or the other did not exist, we might've not been able to survive. Tis demonstrates how vital they are for the human body. 
 
        
             
        
        
        
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Explanation:
absolute age(true age) The age of a geologic phenomenon measured in present Earth years, rather than its age relative to other geologic phenomena (compare relative age)
 
        
                    
             
        
        
        
A habitat defines the interaction of organisms with the other factors, which can be living or non-living, while niche describes how that specific organism is linked with its physical and biological environment. Habitat is the part of the ecosystem, while niche plays an important role in the formation of an ecosystem.