Matching Pairs Define Ecological RelationshipOnline version Define Ecological Relationships by Amanda O'Malley 1 Predation 2 Parasitism 3 Commensalism 4 Competition 5 Mutualism Organisms competing for the same limited resource. One organism is harmed and the other benefits. Both organisms benefit by their association with eachother. One organism benefits, the other is neutral (unharmed but does not benefit). One organism eats another organism.