The often-stated goal of ecology is to understand the distribution and abundance of organisms. Although this quest must include influences of history, the physical environment, and species interactions, food web dynamics is unarguably of central importance. My seminar will focus on the work my colleagues and I have done on sea otters and kelp forest food webs over the past half century. I will begin with a description of the key species and how they connect with one another via consumer-prey interactions. After explaining how sea otters initiate a trophic cascade that reaches downward through the food web to autotrophs and from there to other species and processes, I will address the following questions: how general is the sea otter-kelp forest trophic cascade across the coastal North Pacific Ocean; how are sea otters and the otter-induced trophic cascade linked to other adjoining ecosystems; what are the evolutionary consequences of strong indirect effects between sea otters and autotrophs and how have these evolutionary effects in turn come to influence food web dynamics; what can we learn about the longer-term dynamics of this system from historical proxies; and to what degree does what we’ve learned or think we know about the sea otter/kelp forest system apply to other species and ecosystems?