> See also: > - Reference # Symbiosis The *stable association of one organism with another* is called **symbiosis** - Shifting environmental conditions may impact the benefit or harm of a symbiotic interaction There are four main symbiotic relationships: - mutualism - commensalism - *parasitism*: an antagonistic interacction in which one partner obtains biochemical precursors and energy from a living victim - competition ## Mutualism **Syntrophy** occurs when one species *benefits from the metabolic products* of another. ## Antagonism Antagonism is often used as a synonym for amensalism. In this type of relationship, one species is destroyed or inhibited while the other remains unaffected - Viruses can be considered antagonistic to all organisms as they require their energy & resources in order to replicate ### Predation (Killing) ### Parasitism (Exploitation) ### Competition Typically neither species benefits during competitive symbiotic relationships Some level of effort needs to be put out by both groups to improve their reproductive success and the only “benefit” is the successful propagation of their species