Description of trophic interactions within ecosystems that takes into account species consuming at multiple .
The concept of food webs is preferable to that of food chains because not only can different species obtain nutrients and energy from different trophic levels but multiple exploiter species may exploit the same species or individual exploiter species may exploit multiple victim species.
Everybody (almost) is everybody else! (OK, yes, that's a bit of an exaggeration, but nonetheless is suggestive of the true complexity of trophic interactions within ecosystems.)
See also the concept of trophic structure.