Ecology is about relationships. You think the human body is complex, and it is, try sorting out how different organisms interact with one another on a landscape scale! What a task! And what marvelous provision. Functioning ecosystems = clean water, clean air, healthy wildlife populations, amazing beauty, endless opportunities for observation and study, and more.
So, let’s make a little order of these myriad relationships. There are many types of relationships between species. There is the remora and the shark, the mycorrhizal fungi and the tree, the brown-head cowbird and the yellow warbler. These three relationships show varying degrees of involvement between participants and varying degrees of benefit.
The remora (Remora remora) has proven to be a bit of an irritant to its shark, whale, or sea turtle hosts, but truly is a mostly harmless freeloader looking to expend as little energy as possible as it makes its way across the ocean floor. This type of relationship is called commensalism. One animal benefits (the remora, with a free ride) and the shark receives no “cost” nor a benefit. Amazingly, the remora uses its dorsal fin as a suction cup creating a vacuum which adheres to its ride.
Mycorrhizal fungi colonize the roots of many plants, especially trees, improving the ability of the plant to absorb nutrients. The tree roots provide a home for the fungi. This is an example of a symbiotic relationship where both organisms benefit.
The brown-headed cowbird is a “nest parasite,” never making a nest of its own but rather dumping its eggs into usually unsuspecting songbirds nests including the yellow warbler but many others as well. Unfortunately for the warbler, the larger cowbird eggs hatch first and often kick out the smaller native eggs or simply outcompete the smaller chicks for food. (I have watched this first hand with hooded warblers in Ohio. The cowbirds are expert scouts, locating nests and waiting for the right moment to unload their offspring). Here we have one clear winner and one clear loser. This is a classic example of parasitism. Be sure to click on the cowbird/warbler link to read about how yellow warblers fight back.