Ecological relationships describe the interactions between and among organisms within their environment. The can be positive, negative or neutral.
Predation can be considered as any interaction between two species where one species is a bit stronger and benefits by obtaining resources from and to the detriment of the other.
Competition occurs when multiple organisms compete for a limited resource that they all need to survive.
Mutualism is a positive interaction that benefits two different species in the community. For example, the mutualistic relationship between alga and fungus that form lichens creating a new beneficial species in the community.
Commensalism is an interaction where one species benefits and the other remains unaffected.
Amensalism is an interaction in which the presence of one species has a negative effect on another, but the first species is unaffected. This could occur as simply as a human walking across a lawn, crushing the lowest level of the community.
