food chain

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A succession of organisms in an ecological community that are linked to each other through the transfer of energy and nutrients, beginning with an autotrophic organism such as a plant and continuing with each organism being consumed by one higher in the chain.
• noun Informal A competitive hierarchy.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun The feeding relationships between species in a biotic community.
• noun idiomatic a hierarchy

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun (ecology) a community of organisms where each member is eaten in turn by another member