What is a food chain?

A food chain is best defined as a sequence of organisms each dependent on the next as a source of food. This concept highlights the direct feeding relationships between organisms, where one organism (the predator) consumes another (the prey) in a linear progression. For example, in a simple food chain, grass may be consumed by a rabbit, which in turn is eaten by a fox. This sequence illustrates how energy and nutrients are transferred from one trophic level to another, starting from primary producers (like plants) to herbivores and then to carnivores.

Understanding this relationship is fundamental in ecology, as it helps illustrate how various species interact and how energy flows through an ecosystem. While options like representing an ecosystem or classifying organisms may incorporate aspects of food chains, the core definition lies in the direct dependency of one organism on another for nutritional sustenance. Thus, option B encapsulates the essence of what defines a food chain accurately.