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Here is a food chain:

Foodchain - cat, bird, caterpillar images Wikipedia (Creative Commons); Mullein image (c) iStockphoto.com

 

 
A wildcat will eat 3 birds every day. These three birds will eat 10 caterpillars each, every day, totaling 30 caterpillars. The 30 caterpillars will eat one small bush together every day.
 
a. In the area that these animals live in, the ecosystem can support 500 small bushes being eaten every day. Calculate the numbers of each animal in the food chain.
 
b. As you go up the food chain, the amount of energy available to the following predator decreases. For this food chain, the amount of energy available decreases by 25% for every level in the chain. Calculate how much more energy the wildcat could obtain from becoming a vegetarian and eating the bush rather than from eating birds.
 
c. One year, a bacteria kills 5000 caterpillars. What effect will this have on the food chain?
 
d. Suppose that the wildcats decide to become vegetarians and eat bushes instead of other animals. How many wildcats could 500 bushes support (ignoring the other animals)?

e. If the wildcats became omnivorous (with some of them eating animals and some eating bushes), how many animals would there be if half of the bushes were eaten by caterpillars and the other half were eaten by wildcats?