Ecosystem relationships include populations of the same species, competition for resources between species, limiting factors that control population sizes, and a carrying capacity that determines how many individuals an ecosystem can support. Symbiotic relationships between species can be mutualistic if both benefit, commensalistic if one benefits and the other is unaffected, or parasitic if one benefits at the expense of the other. Predator-prey interactions involve predators consuming other organisms as prey, while cooperation occurs when organisms work together for common goals.