<span>by collecting “proxy data” from tree rings, ice cores, and historical records</span>
        
             
        
        
        
This example reflects the food chain. 
<span>The food chain describes relationships among the organisms by showing how the organisms are related to each other by the food they eat. The food chain contains levels and each of them presents a different trophic level (position of the organism in that chain). There is reliable energy transfer through each stage of the chain. Not all the energy at one stage is absorbed by the organism at the next stage but, the amount of energy from one stage to another decreases.</span>
        
             
        
        
        
Why is the active site specific for only one type of substrate? Enzymes have a lock and key type fit so only a specific substrate fits in the activation site.