Introduction

The chapter opens with a familiar picture — a pond, lake or pool — to introduce the idea of an ecosystem. Looking closely at such a water body reveals a mix of components: mud, dissolved nutrients and gases, clay, plankton and other microorganisms, plants such as algae, Hydrilla, Nelumbo and Nymphaea, and animals ranging from fish and frogs to tortoises, snakes and cranes — together, this whole assemblage of living and non-living parts is what is meant by an ecosystem. More generally, plants and animals (the living components) are always interacting with the surrounding space components — air, water, soil, sunlight and so on. Photosynthesis is a familiar example of this exchange: a plant draws in sunlight, water, carbon dioxide and soil nutrients, and releases oxygen back to the atmosphere, showing that materials genuinely move between the living and non-living parts of a system. The term ecosystem itself was proposed by A.G. Tansley in 1935, who defined it as the system that results from integrating all the living and non-living factors of an environment; Odum (1962) later defined it more compactly as the structural and functional unit of ecology. Various other ecologists coined roughly parallel terms for the same idea over the years — biocoenosis (Karl Mobius), microcosm (S.A. Forbes), geobiocoenosis (V.V. Dokuchaev and G.F. Morozov), holocoen (Friederichs), biosystem (Thienemann), and bioinert body (Vernadsky).