Food chain
In simplest terms, a food chain is the flow of energy from one organism to the next. Food chains are a lot simpler than food webs because food chains show a very simple path that shows what usually happens in nature. Food chains don't really show all the multiple species the animals eat or all the multiple species the animals get eaten by. Food chains just show a simple diagram of how the energy gets passed on.

Food Webs
          Food webs are much more complex then food chains. They show many animals and the many animals it eats.  It also shows the many animals that get eaten by other animals.

Food webs and food chains help out the environment and keep all the populations down.  Food chains show how the energy gets from the plants to the herbivores and then to the carnivores.  Food webs show all the different relationships between the animals

Ecology
Muskrat
By Keanan Fox
bibliography
http://en.wikipedia.org/wiki/Food_chain