Competition is an interaction between organisms or species in which both the organisms or species are harmed. Limited supply of at least one resource used by both can be a factor. This example is if two lions get into a fight and they end up hurting each other.
Exploitation competition occurs when individuals interact indirectly as they compete for common resources, like territory, prey or food. An example of this is when people are farming and they are trying to get the best food available but someone else might have already gotten it.
Commensalism is a positive type of ecological interaction between two species in an ecosystem. In commensalism, the association occurs between members of two different species where one species is benefited the other is neither benefited nor harmed. An example of this is tree frogs who use trees as protection.
Other than contributing to potential increase in diversity of species in an ecosystem, exotic species have positive benefits like removing toxins from the soil, regulating erosion, and controlling undesirable species.
