What is a food chain?

A food chain is best defined as a linear sequence of organisms through which nutrients and energy pass. This description captures the fundamental concept of how energy flows through an ecosystem, starting from primary producers like plants, which convert sunlight into energy through photosynthesis, and moving up to primary consumers (herbivores), and then to secondary and tertiary consumers (carnivores). Each step in this sequence represents a transfer of energy as one organism is consumed by another, highlighting the straightforward nature of these interactions.

In contrast, a complex network of feeding interactions represents a food web, which is a more intricate and holistic view of the feeding relationships in an ecosystem, integrating multiple food chains. A pyramid representing trophic levels visually illustrates the distribution of biomass or energy among different levels of a food chain but does not define what a food chain is. Lastly, a model of population dynamics focuses on how populations of species change over time and does not specifically address the energy transfer aspect depicted in a food chain. Thus, the choice highlighting the linear sequence is the most accurate definition of a food chain.