In nature, organisms interact with each other in a variety of ways. Some are predators, some are prey, and some just compete for food against each other. Some of these relationships last a long time while others do not. In nature a relationship between two organisms that last a long time is called symbiosis. There are different kinds of symbiosis. There are times when both organisms in the relationship benefit from each other. There are times when only one will benefit while harming the other. Then there are times when only one benefits, but no harm is done to the other.
When a relationship between two kinds of organisms benefits both organisms, it is called mutualism. For example, in The Mojave Desert there is a plant that exists called the Yucca tree. When this tree's creamy flowers are in bloom there appears to be shadows that jump around on the flowers. However, a more careful look reveals that these shadows are actually moths. They are called yucca moths. The yucca moths cannot survive without the yucca tree. The yucca trees would also quickly become extinct if it were not for the yucca moth. The yucca moth visits the yucca flower at night and picks up pollen and rolls it up into a ball. The moth then flutters over to another flower and implants that pollen into that flower's ovary. The moth is able to pollinate the flower which in turn sprouts new seeds that become new yucca plants. The yucca tree and the yucca moth depend on each other for survival and they both benefit and share a relationship of mutualism.
When two organisms form a relationship where one organism lives on or in another organism and may harm the other in the process it is called parasitism. The organism that lives on or in the other is called a parasite. The organisms they feed on both are called hosts. The parasites benefits from the relationship. The hosts are harmed by the relationship. For example, fleas are parasites of dogs. The fleas feed off the blood of the dog and give nothing back to the dog in return. The host is harmed while the parasite benefits. Another example of parasitism is mistletoe. It is an evergreen that grows in the branches of a tree such as a poplar, fir, or apple. The mistletoe feeds off the tree while offering nothing to benefit the tree. The relationship between these two organisms is called parasitism.
The relationship between two organisms where one benefits from the other while causing no harm in the process is called commensalism. An example of this would be when a tropical fish lives unharmed among the poisonous tentacles of a sea creature. The sea creature provides safety for the fish and the fish neither harms nor helps the creature. The fish becomes protected from other predators by the poison, yet provides nothing to the sea creature. Another example is when orchids attach itself to the trunk of a tree on the rain forest floor. The orchid only attaches itself to benefit from the position of the tree in order to get sunlight. It causes no harm to the tree. This relationship is called commensalism.
There are different kinds of symbiosis. Each defines the relationship between organisms in nature. While some organisms are predators, other becomes the prey. Still other organisms can live together without any harm being caused. Whether these relationships are mutualism, parasitism, or commensalism, it is clear that organisms interact with one another in a variety of different ways. The nature of these relationships and how they interact differently together is called symbiosis.