In this instructional activity, students compare various types of relationships among organisms (i.e., biotic interactions). Students will: explain the roles of producers and consumers, and predators and prey in an ecosystem. Explain the levels of order in an ecosystem from simple to complex (i.e., individual, community, population, and ecosystem). Use evidence to infer the relationship between changes in predator and prey populations. compare symbiotic relationships among organisms (i.e., parasitism, mutualism, commensalism, and amensalism).