In this activity, students model trophic cascades using cards of organisms from seven different habitats. The activity is designed to illustrate the species relationships in a food chain and the effect of predators on the trophic levels below.

Trophic cascades have been described in numerous ecosystems, ranging from kelp forests of the Pacific Ocean, to arctic islands, to Central American jungles, to salt marshes. They occur when predators reduce the abundance or change the activity of their prey, thereby allowing species in the trophic level below to increase in number. These indirect effects by the predator can trickle down (or cascade) to many lower levels of the food chain. In a classic example, sea otters protect kelp forests by controlling the abundance of urchins that graze upon the kelp. In the absence of otters, urchins consume most of the kelp and negatively affect other organisms that live in kelp forests.

This activity complements the concepts explored in other BioInteractive resources, including the Exploring Trophic Cascades Click & Learn and the short film Some Animals Are More Equal than Others: Keystone Species and Trophic Cascades.

The “Card Images” ZIP file contains individual image files for the cards used in this activity that can be used in the classroom, particularly in online courses. A document within the ZIP file contains suggestions for their use. These card images are licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International (CC BY-NC-SA 4.0) license. We would ask that you attribute these to BioInteractive and not use them for commercial purposes.