Final answer:
A food web, which accounts for multiple trophic interactions between species, is a more accurate description of ecosystem structure than a food chain that follows a linear sequence.
Step-by-step explanation:
A food chain is a linear sequence of organisms through which nutrients and energy pass, with each organism occupying a specific trophic level. However, food chains are limited in accurately describing ecosystems because some organisms can feed on more than one trophic level and can be eaten by species from multiple trophic levels. Instead, a more accurate and descriptive model for ecosystems is a food web, which accounts for the multiple trophic interactions between species. In a food web, there are several trophic connections between each species and other species that interact with it, crossing multiple trophic levels. Therefore, the best summary of the model is option 2) a series of trophic levels.