you are likely to find Potato in/at/on Stomach. you are likely to find Food in/at/on Stomach. Food is related to Duck. Duck is related to Fly. 
Condition is part of Experiment. 
Potato --AtLocation--> Stomach <--AtLocation-- Food <--RelatedTo--> Duck <--RelatedTo--> Fly 
Condition --PartOf--> Experiment 