Ecosystem as a Unit of Nature
An ecosystem can be visualised as a functional unit of nature representing complex interactions between living and non-living components. The study of any ecosystem involves systematic description of the components and understanding of the close relationship between the biotic and the abiotic components. Why consider ecosystem as a unit of study? This, perhaps, is the question arising in your mind presently. If one wishes to study the various aspects of relationships of living and non-Jiving components of the environment, it would be easy to understand and interpret these relationships in a smaller component of the biosphere that is the ecosystem. We shall elaborate this further with the help of an example. Let us consider a village ecosystem. It is depicted here by the area enclosed within the dotted lines. The boxes within the village ecosystem represent three sub-systems namely: producers or 'crop plants, cattle and humans. The solid lines connecting the boxes represent the interactions. Solar energy, fertilisers and pesticides are the major inputs brought from outside the village ecosystem. These inputs determine the quantum of output, that is, food grain, fodder and other animal products which are exported from the village. So, you see that, the village ecosystem could be considered as a model to study the organisms and their environment as an integrated unit.
Figure: A model of village ecosystem
Ecosystems are conceptual models and these models can be applied at any scale, from a bowl of water to the whole earth. Ecosystems represent enormous contrast in size and complexity. For the purpose of study, an ecosystem can be delineated in almost any way convenient to the interest of the investigator. In the case of some ecosystems such as lake, river or pond, distinct boundaries can be recognised but in the case of other ecosystems, such as a grassland, forest, village or town, boundaries are not so sharp however, they can be delineated according to the object of study or any other practical consideration.