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ABSTRACT Studies of symbiosis employ the term “parasitism” to connote different sorts of relationships. Within the context of mutualistic symbioses, parasites are otherwise cooperative individuals or strains that appropriate a disproportionate amount of the synergistic products. In the context of antagonistic symbioses, there is no pretence of cooperation, and instead parasites are defined as individuals or strains that derive fitness benefits at a fitness cost to their hosts. In both cases, parasitism is selected for at the lower level (that of the individual symbiont) but selected against at the higher level (the group of symbionts in a single host). Despite these similarities, these different sorts of parasitism likely evolve by different pathways. Once a host–symbiont relationship initiates, if functional synergy is lacking, the relationship will remain exploitative, although parasites may differ in their detrimental effects on the host and the higher‐level unit. If functional synergy is present, however, cooperation may develop with benefits for both host and symbionts (i.e. mutualism). Nevertheless, parasites may still evolve from within these incipient relationships when individuals or strains of symbionts act parasitically by defecting from the common good to further their selfish replication. Levels‐of‐selection dynamics thus underlie both forms of parasitism, but only in the case of latent functional synergy can true symbiotic complexity at the higher level emerge. 

Inquiry-based lessons allow learning that is hands-on and student-driven, fostering engagement and retention of knowledge in any discipline. Here, we use this learning framework to engage students in exploring the effects of biotic and abiotic factors on animal dispersal as a means of connecting students to multiple ecological concepts. Instructors are provided with a guided lecture on key ecological concepts including the impacts of invasive species, dispersal mechanisms, and species interactions with the environment. Furthermore, the interactive lecture introduces students to the snail study system and explains the experimental process, which involves low-cost, readily available materials (e.g., kiddie pools). Students design experiments that explore how variables including density, substrate, and temperature can affect animal dispersal. They conduct the experiments, engage in a process of peer-review, analyze results, and share their study. We performed this lesson in an undergraduate Ecology course and report here on student responses to the experience. The lesson is designed to be performed with the faucet snail (Bithynia tentaculata), an invasive freshwater species throughout much of the Great Lakes region, but can be easily modified to accommodate other species. The lesson is also highly amenable to modifications for variable class sizes, student grade levels, and lesson duration.