The distinction between a primary consumer and a secondary consumer lies in their position within the food chain. Primary consumers are typically herbivores that feed directly on primary producers, such as plants or phytoplankton. In contrast, secondary consumers are carnivores or omnivores that feed on primary consumers. This hierarchical structuring of consumers illustrates the flow of energy and nutrients through an ecosystem. Understanding these roles helps ecologists assess interactions within food webs and the overall balance of ecosystem dynamics.