<P> Mutualism is the way two organisms of different species exist in a relationship in which each individual benefits from the activity of the other . Similar interactions within a species are known as co-operation . Mutualism can be contrasted with interspecific competition, in which each species experiences reduced fitness, and exploitation, or parasitism, in which one species benefits at the "expense" of the other . Symbiosis involves two species living in close proximity and includes relationships that are mutualistic, parasitic, and commensal . Symbiotic relationships are sometimes, but not always, mutualistic . </P> <P> A well - known example of mutualism is the relationship between ungulates (such as bovines) and bacteria within their intestines . The ungulates benefit from the cellulase produced by the bacteria, which facilitates digestion; the bacteria benefit from having a stable supply of nutrients in the host environment . This can also be found in many many different symbiotic relationships . </P>

Biological groups of organisms interacting with each other and the physical environment is a(n)