Expert: Walter Hintz - 7/21/2006

Question
When a brown bear eats a salmon, does the bear acquire all the energy contained in the body of the fish? Why or why not? What implications do you think this answer would have for the relative abundance (by weight) of predators and their prey?  Does the second law of thermodynamics help explain the title of the book Why Big, Fierce Animals are Rare?  

Answer
 No.The second states that with any conversion of energy from one form to another this a loss of useful energy.  The bear converts the chemical energy in the fish to heat.  Here is an example of an energy pyramid

                   Bear eats salmon
                 Salmon eats fish
                Bigger fish eats them
               small fish eating them
           Small water animals eating plants
          Small water plants making glucose

    Now consider: It take 10 # of plants plants to make 1 # of small animals
  It takes 10 # of small animals to make 1 # of small fish
  It takes 10 # of small to make 1# of big fish
  It takes 10 # of bigger fish to make a # of salmon
  It takes 10 g# of salmon to make 1 # of bear

So how many ponds of plants are needed to make 1 # of bear
             10x 10x 10x 10x 10x 10

This should answer the question