The term 'ecological stages' refers to the different stages of development that an ecosystem goes through. The term SERES is a five-letter word that is used to describe these stages. SERES stands for Succession, Eutrophication, Recovery, Equilibrium, and Succession. Succession is the process of change in an ecosystem over time, while eutrophication is the process of nutrient enrichment in an ecosystem. Recovery is the process of restoring an ecosystem to its original state, and equilibrium is the balance between biotic and abiotic components of an ecosystem. Finally, succession is the process of re-establishing the original ecosystem after a disturbance.