Claude Levi-Strauss used “floating signifier” to refer to terms with meaning only in a given cultural context. Derrida of course would argue that all words are floating signifiers. I’m not sure what he means.
“Symbiosis” is one such floating signifier. Last weekend my brother in law’s future brother in law described a parasite he had once had.
Sensible people at this point in a conversation either keep their trap shut or head for the bar. I’m not sensible, so after returning from the bar I turned on the mouth. I’m sure they were all thinking “note to self future brother of brother in law = bloviator.” I pointed out that, at least in biology textbooks, symbiosis does not necessarily mean a relationship that is mutually beneficial: it just means organisms living in a close physical proximity — often contact. He could call his parasite a symbiont and didn’t that sound nicer?
There are three types of symbiosis: commensalism, where one organism benefits and the other is unharmed; mutualism, where both organisms benefit; and parasitism where one organism benefits and the other is harmed.
Examples or parasitism and mutualism are pretty easy to think of. For instance, most politicians are parasites. They require the host (the nation) to stay alive just enough to continue sucking their sustenance. Mutualistic symbioses include our gut bacteria: we give them a home and they help us digest things.
Commensal interactions are a bit unusual. Some epiphytic plants, like orchids and bromeliads don’t harm the tree they grow in. Bromeliads form a cup with their leaves and this can make a habitat for little frogs and insects which don’t harm the bromeliad or the tree it lives in. A good example is the Guyanese golden bromeliad frog. That’s really an organism, I didn’t just make it up.
After they chased me out of the little party, I looked at my driveway and noted that it was covered in maple fruit (some people call them whirlybirds). Whereas humans and other top of the food-chain type organisms tend to raise few young and put a lot of time into them, most producer organisms use the opposite tactic: they produce lots of potential offspring. Most of these get eaten by insects, fungi, small creepy animals, and other beasties. These fruits end up feeding all the other creatures that don’t produce anything on their own.
When the American chestnut was killed off by blight, the loss dramatically altered the trophic web of the Atlantic seaboard. According to a paper from 2000 in the Journal of Applied Forestry by Diamond et al there was a decrease in the hard mast of the forest by about one third, but also a decrease in the stability from year to year. That meant the animals (turkey, deer, mice, squirrels, and bigfoot) had less to eat.
In broad strokes, where do symbioses end? Is it the physical interaction only? The remora fish on a shark is a symbiotic relationship, but the bird that chases after herds in the African plains to eat the stirred up insects is not. I would suggest that both are symbiotic relationships and that there are few relationships which aren’t. In a biological community the organisms all depend on each other for something. Certain politicians might do well to remember that.