This document discusses food webs, ecological pyramids, and energy transfer between organisms through a classroom activity called Deadly Links. It explains that food webs show interconnected food chains and ecological pyramids illustrate how energy decreases at each trophic level. The activity simulates bioaccumulation of toxins up the food chain. Students role-play as grasshoppers, shrews and hawks to understand predator-prey relationships and how toxins concentrate in top carnivores.