Species Interaction
Species can interact in different ways. Some species may benefit from sharing a common space with another species for several different reasons (complementarity), however, some other species may experience negative effects when sharing a common space with certain species (competition).
Competition can be defined as the direct or indirect interaction of organisms that leads to a change in fitness when the organisms share the same resource. The outcome usually has negative effects on the weaker competitors. Species may compete for nutrients (nitrogen, phosphorus, sulfur, iron...), prey, water etc. But species can also compete for the physical space required to live. Typically, the species will compete for the resource that is limiting.
The types of competition can be divided in "interspecific competition" and "intraspecific competition". Interspecific competition refers to the competition between individuals of different species. However, intraspecific competition refers to the competition between individuals of the same species.