Ecosystem refers to a unified whole composed of biological communities and inorganic environments. The scope of an ecosystem can be large or small, intertwined, and the largest ecosystem is the biosphere. The ecosystem is an open system. In order to maintain its stability, the ecosystem needs to be continuously Enter energy, otherwise, there is danger of collapse. Among the following, what constitutes an ecosystem:. ['Species, plants and animals in the primary-secondary forest.', 'Sunlight, soil, various plants and animals in farmland.', 'Grazing herds, tour teams and tourists in grassland pastures.', 'Microbes, algae, small fish and shrimp in the pond.']