Symbiosis

The term “symbiosis” was coined by the German microbiologist Anton de Bary circa 1878 to describe an association between different species that persists for a long time. There are two types of symbiosis—endo- and exosymbiosis. Endosymbiosis involves the union of different genomes at either the nuclear or cytoplasmic levels; and exosymbiosis describes all other forms of symbiosis.

A fascinating example of exosymbiosis is the “ant tree” of French Guiana, described by Russ Mittermeier: “They [ant trees] are plants that have coevolved with species of ants for their mutual benefit. The trees often have hollow stems in which the ants live and raise their young. Some plants go so far as to have developed specialized structures that produce nutrient-rich solutions on which the ants feed. In return, the ants viciously attack insects or other intruders that might damage the tree. Some ants also devour vines, stranglers, and lianas that climb onto their host plant. In the most extreme cases, the insects clear away all vegetation within a several-foot radius. Debris from the ant nests inside the tree fertilize the plant. Some of these ants and trees rely on each other to such a great degree that one cannot survive without the other.” (Plotkin, 46)

Symbiogenesis

In 1897, the American lichenologist Albert Schneider published a seminal paper in the Minnesota Botanical Studies that opened with the declaration, “All living organisms manifest a more or less intimate biological interdependence and relationship.” (Ryan, 50) For Schneider, Ryan writes, the only “true symbiosis” was “an interaction between species at the physiological level. The intimacy and intensity of such a relationship would inevitably change the chemistry and even the physical make-up of one or both symbionts. Moreover, he saw that such a change must be controlled and passed on in a hereditary manner. Suddenly a new clarity of vision appeared. Schneider realized that symbiosis was far more than a curiosity in nature: it could create important evolutionary change.” (Ryan, 51)

Could symbiotic interactivity result in the appearance of new tissue, new organs? This question was addressed by a number of biologists in the early decades of the twentieth century, such as the Russian scientists Andrei S. Famintsyn and Konstantine Merezhkovskii. In 1906, Famintsyn claimed that he managed to grow organelles from the living cells of “lower animals.” He became convinced that evolution is the result of a “consortia” of simpler life forms. (Ryan, 52) In 1910, Merezhkovskii coined the term symbiogenesis to signify evolutionary change as the result of symbiosis.