interorganismic

Interorganismic is an adjective used in biology to describe processes, interactions, or phenomena that occur between different organisms, as opposed to intraorganismic processes that occur within a single organism. The term is common in ecology, evolutionary biology, and studies of symbiosis and community dynamics, where attention is on how organisms influence each other's survival, reproduction, and behavior.

Interorganismic interactions span a wide range of relationships, including competition for resources, predation, parasitism, mutualism, commensalism, and various forms of symbiosis. These interactions shape individual fitness, population dynamics, species distributions, and ecosystem structure, and they often drive coevolution, whereby species reciprocally adapt in response to one another.

In evolutionary theory, interorganismic selection describes selection pressures that arise from interactions among different organisms, such as pathogens shaping host defenses or mutualists constraining cheating. Researchers also distinguish between interorganismic processes that operate between species and those occurring among individuals within a species, the latter sometimes called social or social-ecological interactions.

Examples include predator–prey cycles, plant–pollinator partnerships, host–parasite dynamics, and coral–algae symbiosis. Studying interorganismic relationships helps explain food webs, community resilience, and the evolution of social behavior.

See also: interspecific interaction, coevolution, symbiosis, mutualism, parasitism, competition.