Answer
The flow of energy and nutrients takes place in an upward direction through different trophic levels in the food web. Trophic cascades occur when the consumer indirectly affects the species that are lower in the food web.
Work Step by Step
The figure showing a vertical food chain in which the sea urchins eat kelp and the sea otters eat sea urchins is depicted below. The kelps are at the bottom as they are the primary producers in this case. The sea urchins are in the middle, while sea otters at the top. The arrows point upward because the flow of energy and nutrients take place from one trophic level up to the next trophic level.
