What distinguishes a food chain from a food web?

A food chain is characterized by its linear structure, showing a straightforward pathway of energy flow through different trophic levels, starting from producers and moving to primary, secondary, and tertiary consumers. It typically illustrates a single sequence, such as grass → rabbit → fox, clearly delineating how energy and nutrients are transferred from one organism to another.

In contrast, a food web is a more complex representation that consists of multiple food chains interconnected with one another. It reflects the various feeding relationships in an ecosystem, capturing the reality that organisms often consume and are consumed by multiple species. Consequently, while a food chain simplifies energy transfer and interactions to a single, unambiguous route, a food web incorporates the numerous interrelations that exist within an ecosystem, making it a more accurate depiction of ecological dynamics.

Other options introduce concepts that do not effectively differentiate between these two ecological terms. For instance, food chains and food webs can both exist within a single ecosystem; both contain producers and consumers; and organisms within both frameworks can span a range of taxa, not just mammals. Thus, the defining feature of a food chain versus a food web indeed lies in the complexity of the relationships depicted.