Simbioza

Simbioza, or symbiosis, is a close and long-term interaction between organisms of different species that live in direct contact. The term was introduced by the German botanist Heinrich Anton de Bary in 1879 and derives from Greek syn ("together") and biosis ("living"). Symbiotic relationships can be mutualistic, commensal, or parasitic, and they may be obligatory (required for survival) or facultative (optional).

Mutualism is a cooperative association in which all partners benefit. Classic examples include lichens (a fungus and a photosynthetic partner such as algae or cyanobacteria), mycorrhizal fungi and plant roots, and the coral-algae symbiosis. In many animals, gut microbes enable digestion or synthesize essential nutrients.

Commensalism describes interactions where one species benefits while the other is largely unaffected. Parasitism is when one organism benefits at the expense of the host, as with tapeworms, fleas, and many plant pathogens. Some relationships are context-dependent and may shift along the spectrum between mutualism and parasitism depending on environmental conditions.

Simbioza is central to ecology and evolution. It drives nutrient cycling—such as nitrogen fixation by rhizobia in legume roots—and shapes communities. Endosymbiotic theory proposes that key organelles, mitochondria and chloroplasts, originated from ancient symbiotic associations. In humans and other animals, the microbiome represents a complex network of symbiotic relationships essential to digestion, immunity, and development.