Every organism needs to obtain energy in order to live. Plants get energy from the sun and animals eat plants or other animals. A food chain is the sequence of what eats what in an ecosystem. The arrows in a food chain show the flow of energy, from the sun or hydrothermal source to a top predator in a single path. The terms food chain and food web both refer to groups of organisms that depend on each other for food. A network of many food chains is called a food web, in which everything is connected. A food chain helps ecologists understand how specific plants and animals depend on one another and as a basis for studying food webs. This Demonstration shows two examples of food webs using the new graph functions introduced in Mathematica 8.