Symbiosis is when two or more different species interact with one another in a relationship.
These relationships are not always beneficial.
There are actually three different types of symbiosis:
- Mutualism - Both creatures benefit.
- Commensalism - Only one creature benefits, but the other isn't harmed.
- Parasitism - Definitely an uneven trade, where one creature may end up dead.
Mutualism happens when different organisms form a biological interaction where both benefit. In other words, both species involved get something out of the deal, whether it be food, a place to live or protection.
The most common form of mutualistic relationships are between flowering plants and animal pollinators.
Flowering plants have a problem—they can't move. Because of this, they have a hard time reproducing. Unless a plant has evolved a different means of exchanging pollen, they need animals to aid them in finding a mate.
These produce flowers containing sweet nectar that is appealing to many types of insects, birds and even mammals. The plants offer up a free meal, and in return, the pollinators willingly (and unknowingly) pick up some pollen from the stamen (male portion) of the flower.
When the pollinator reaches another flower on a different or even the same plant, the pollen may rub off into the pistil (female portion). This leads to fertilization and eventually reproduction.
Human beings and bacteria
Did you know that you have 10 times more bacterial cells in your body than human ones? Well, it's true, and we couldn't live without them!
In our gut, there are many different kinds of bacteria that aid us in the digestion process. These bacteria break down substances our digestive system can't. We provide them with an endless source of energy, and in return, they help us digest our food properly. In addition, these bacteria also help us establish a healthy immune system.
Zooxanthellae and coral
Another amazing example of mutualism is the relationship between zooxanthellae, which are microscopic and photosynthetic protists, and coral.
Since zooxanthellae are photosynthetic, they make sugar using the energy in sunlight. These zooxanthellae actually are found living in the tissues of some corals. The coral provide shelter and nutrients to the zooxanthellae and, in return, the zooxanthellae provide sugars.
Clown fish and sea anemones
Sea anemones are carnivores that trap and disable prey with stinging harpoons on their tentacles. Clown fish are immune to the toxins of the anemones and actually reside within their deadly tentacles.
The anemone provides shelter and even food for the clown fish. The clown fish are protected by the tentacles from predators and gain a meal or two by eating the anemone's dead tentacles and feasting on morsels left over by the anemone.
In return, the clown fish help attract prey for the anemone to eat and provide a fertilizing feces that helps nourish the anemone.
Commensalism is a biological relationship in which one organism benefits in some way and the other is harmlessly unaffected.
Grazing animals and birds
Have you ever watched the Discovery Channel or National Geographic Channel and saw a large ox or a water buffalo walking through a field. Chances are some of those oxen and buffalo had birds perched on their backs.
The reason these birds do this, aside from looking cool, is the large grazing animals kick up lots of flying insects in the process. These insects fly away and scatter. In the frenzy, the bird has a smorgasbord of insects that it can literally pluck out of the sky!
As you can see, the bird benefits, while the animal grazer couldn't care less.
Whales and barnacles
Whales and sea turtles are regularly seen with barnacles on parts of their bodies. These barnacles are crustaceans that have anchored themselves to the underbelly of whales and the shells of turtles.
The reason barnacles do this is because both whales and turtles migrate incredibly long distances. This supplies the barnacles with an endless supply of new, fresh food. Sometimes, the barnacles get some of their host's leftovers. These little guys can even grow on boat bottoms.
Parasitism is a biological relationship where one organism gains or benefits, while the other one is harmed in some way, or even killed.
Humans (mammals) and ticks
Anyone who has ever hiked, fished, or been outside for a long period of time has probably found a tick on themselves before.
The tick attaches to our skin and makes a puncture where it feeds on our blood. The tick becomes engorged and therefore benefits. On the other hand, us mammals have the delight of having a tick feeding on us and the chance of getting an infection or Lyme's disease—clearly not beneficial.
Parasitic worms and grasshoppers
There is a certain type of worm that invades grasshoppers. These worms grow and mature inside the body cavity of the host grasshopper.
When they reach maturity, the worms secrete a type of protein that interacts with and eventually takes over the grasshopper's central nervous system.
Eventually, the grasshopper loses control and jumps into a body of water, killing itself.
At this point, the parasitic worms leave the grasshopper via the abdomen and start the reproductive portion of their life cycle, which happens in the water.
These interesting relationships are very common in the biological spectrum, and even help shape the food chain. What would happen in some of these relationships were disrupted? Think about it!