What is a trophic cascade and what is a food web?

• A. A simple linear chain of who eats whom; no indirect effects.
• B. A food web is a network of feeding relationships; a trophic cascade is indirect effects of predators on lower trophic levels via changes in prey abundance.
• C. A food web is a linear path from producers to apex predator; a trophic cascade is the energy lost as heat.
• D. A food web describes only herbivores; a trophic cascade is when prey populations collapse.

Answer: (B)

Understanding how predators influence ecosystems through indirect effects and how feeding relationships form a network. A food web is the network of who eats whom across producers, consumers, and decomposers, showing multiple feeding pathways that energy and nutrients follow through an ecosystem. A trophic cascade is a specific pattern within that web where changes in a top predator cascade down to affect lower trophic levels, often through changes in prey abundance, which can then influence vegetation and other parts of the ecosystem. For example, predators that reduce herbivore numbers can allow vegetation to rebound, which then benefits many other species.

The description that matches this idea says a food web is a network of feeding relationships, and a trophic cascade involves indirect effects of predators on lower trophic levels via changes in prey abundance. The other ideas fall short because they treat the food web as a single, linear chain with no indirect effects, or they misdefine trophic cascade as energy lost as heat or as something limited to herbivores, which doesn’t capture the real, interconnected dynamics.