Symbiosis is a close, usually long-term interaction between two or more different species; until 1877, it referred to people living together in community. Some symbiotic relationships are obligate (meaning that both participants, or symbionts, are entirely dependent upon each other for survival), while others are facultative, meaning that they can exist symbiotically, but they don’t need to in order to survive. Symbiosis is usually associated with animals which live and function for mutual benefit, though many plants (such as lichens) are also symbiotic. In nature, sea anemones and clownfish are among the best-known symbiotic animals: the clownfish feeds on smaller animals which would otherwise harm the anemone, and the anemone feeds on the clownfish’s leaving and protects it from predators with its stinging cells, which the clownfish is immune to. Not all interspecies relationships are symbiotic; the interactions between humans and fleas, for instance, are parasitic rather than symbiotic, as only the flea benefits from this and acts as a pest towards the human.
InGen engineered a facultative symbiotic relationship between two of the dinosaur species they cloned: the Apatosaurus and the Procompsognathus. The apatosaurs (and presumably other large herbivores) lacked bacteria in their digestive tracts which properly broke down their food. To remedy this, InGen’s scientists redesigned the procompsognathids so that they could consume and break down the apatosaurs’ fecal matter further as a means of waste control in the park.