What are the major differences between a natural ecosystem and a microcosm that affect biodiversity and population density?
The three biggest differences are the dimensions of size and time, and the impact of the sun (and thereby, the weather). 1) Size. Even small natural ecosystems are typically enormous compared to artificial models. Furthermore, natural ecosystems are extensively subdivided into innumerable microhabitats created by physical heterogeneity and distance. Ultimately all natural ecosystems are partially separated sub-divisions of the global biosphere with perpetual migration of species occurring throughout the system. The vast size of the biosphere creates considerable buffering of chemical changes and huge stockpiles of available resources. 2) Time. Natural ecosystems have the benefit of long periods of time to allow chemical equilibration, rare immigration events and adaptive radiation of species to occupy new or unexploited niches. 3) Sunlight. The sun provides the energy for photosynthesis and other important light dependent reactions that allow the biosphere to cycle and process resource
