Learning Objectives

21.3.1 Compare the factors that influence energy flow in an ecosystem between bottom-up and top-down perspectives.

21.3.2 Describe how changes in the abundance of organisms at the fourth trophic level may impact rates of primary production through a trophic cascade.

21.3.3 Explain how the size of an ecosystem, the rates of disturbance, and the amount of primary production can influence the number of trophic levels.