This document discusses ecological relationships between living organisms. It defines symbiosis as a close relationship where at least one organism benefits. The three main types of symbiotic relationships discussed are mutualism, commensalism, and parasitism. Examples of each relationship type are provided, such as cleaner shrimp and grouper fish in a mutualism relationship, and barnacles attaching to grey whales in a commensalism relationship. Activities are included to help students identify and classify different ecological relationships.