A symbiotic relationship is one in which both parties benefit. Some of these are stranger than others, and some even manage to benefit those outside the relationship. For instance, consider Laurel and Hardy. Stan Laurel, the Englishman, had already had a long career in variety and silent films just as the Georgia native, Oliver Hardy, had had an equally long apprenticeship in vaudeville and the movies before Hal Roach had a brainstorm and teamed them up. The end result was much better than the sum of its parts as proven by the fact that after 80 years the boys are still garnering belly laughs.

Another terrific example was Ginger Rogers and Fred Astaire. She had already appeared in several forgettable movies without causing much of a stir, while Astaire, after making a screen test which led one studio executive to observe that, although he could sing a little and dance a little, he was skinny, balding and looked like a whippet. However, once they were teamed up in “Flying Down to Rio,” they went on to make motion picture history in such movies as “Top Hat,” “Carefree” and “The Gay Divorcee.” In describing the special magic they had together, someone concluded that he gave her class and she gave him sex appeal.

Mother Nature provides an extraordinary example of a symbiotic relationship -- the one that exists between sharks and pilot fish. The shark could have pilots for breakfast, lunch, dinner and a midnight snack. But the little guys are never on the sharks’ menu because the pilots provide them with an indispensable service; they act as nautical toothpicks, picking out bits of food that would otherwise collect and lead to tooth decay and, I assume, gum disease. In short, the pilots are a lot like Hollywood gofers except that they don’t have to chauffeur the stars’ kids and collect the dry cleaning. They’re also paid better, shown more respect and, occasionally, the sharks even bother learning their names.

There are other examples of such relationships, and one of the unfortunate ones that leaps to mind is that which exists between liberal politicians and those engaged in show business. People might assume that it’s a one-way street and that it’s only the office holders who benefit. They, after all, receive multi-millions of dollars from the likes of Barbra Streisand, Alec Baldwin, Larry David, George Clooney, Oprah Winfrey, Billy Crystal, Susan Sarandon, Tim Robbins, Martin Sheen, David Geffen, Steven Spielberg, Robert Redford, Jane Fonda, Bruce Springsteen, Michael Moore, Sean Penn and the Dixie Chicks. It’s not just the checks they write themselves, but the fund-raising events they host and at which they appear that help fill the campaign coffers of such people as Hillary Clinton, John Edwards and Barack Obama.

But what, you ask, do the politicians provide in return? It’s the one thing that these celebrities crave so desperately, and which their gaggle of agents, managers, publicists and assorted sycophants simply can’t deliver; namely, gravitas. It’s not enough, after all, that the world envy them their fame and fortune. These assorted high school drop-outs and high maintenance nincompoops want to be taken seriously.

So, when you see Leonardo DiCaprio standing beside Al Gore as the Nobel laureate prattles on about global warming, the subliminal message is that young DiCaprio could be off somewhere frolicking with bimbos and working on his tan, but because he’s a serious fellow with grave matters on his mind, he’s right there on stage trying to stay awake and look intelligent.

And after the speech, what then? Well, I’m not sure, but I’ve always assumed that DiCaprio sticks around for a while and helps Mr. Gore floss his teeth.