This document defines key terms related to ecosystems, including biotic and abiotic factors, producers, consumers, and decomposers. It describes the structure and functions of ecosystems, including energy flow and food chains/webs. Various types of ecosystems are classified, such as terrestrial (forest, grassland, mountain), freshwater (lentic and lotic), and marine. Specific examples like forest, desert, pond/lake, and ocean ecosystems are outlined, defining their biotic and abiotic components.