For food and resources. Types: interference (by direct attack), exploitation (forced to share a resource), scramble (everyone gets something), contest (one competitor gets it all), and restrictive (preventing someone else from getting it); also, inter- and intraspecific modes (between or within species). Competition tends to characterize less mature ecosystems. Note: there is some debate about how much of the "competition" and "dominance" we see in the natural world is projected there by observers who take such behaviors in overmanaged human societies for granted.