Competition and predation are two key factors that affect the stability of an ecosystem, such as a lake. There are three theories about the effects of competition. Competition can lead to competitive exclusion, stable coexistence or niche differentiation. It has been shown that in marine environments, species are strong competitors for light and nutrients and that competition therefore only leads to competitive exclusion (Passarge et al. 2006). The principle of competitive exclusion states that if two species compete for the same resource in the same place, then one of these species will disappear because one of them will be the better competitor (Jenson 2010). Another factor in ecosystem diversity is predation. The predator-prey relationship is complex. Populations go through cycles of high abundance and low abundance. There is ample evidence that predators are capable of reducing prey populations in density-dependent situations (Freeman 2008). An example is the study of snowshoe and lynx hair. This study proved that hair populations and lynx...