This article describes an interactive lesson in which the complexity of food webs and ecosystems is explored. Students generate a list of organisms in a Pacific aquatic ecosystem, assign each organism to a student, and then link the organisms together in a food web using string. Students tug on the string to identify the connections in the food web. In response to several potential changes the teacher describes, the students tug on their strings to predict patterns of interactions. Next, they investigate the limiting factors in an ecosystem. As a concluding activity, students respond to how organisms are affected with differing "Interdependence Scenarios."