Symbiosis comes from two Greek words that mean "with" and "living." It describes an ecological relationship between two organisms from different species that is sometimes, but not always, beneficial to both parties. Keep reading to learn about the different types of symbiosis and how they provide balance in various ecosystems around the world.
Types of Symbiosis
There are several kinds of symbiosis to consider when looking for symbiosis examples. Each type is often found in a habitat, but some are more common than others. The most common types of symbiosis include:
- mutualism - a mutually beneficial symbiotic relationship
- commensalism - a one-sided symbiotic relationship
- parasitism - one species lives on, in or with a host species
- competition - relationship in which organisms compete for resources
- predation and herbivory - symbiosis where one organism feeds on another
These symbiotic relationships are different based on which species benefits the most and whether they can live without each other. However, each one allows an ecosystem to reach a sustainable balance.
When people use the word symbiosis, they’re usually talking about a mutualistic symbiotic relationship. Mutualism is a close, long-lasting relationship where both parties benefit. Organisms can use other organisms for cleaning, protection or gathering food. In some mutualistic relationships, the organisms can’t survive without each other.
Some examples of mutualism in nature include:
- Cleaner wrasse live in “cleaning stations” in a reef. They remove and eat parasites, dead tissue and mucous from reef fish, which helps reef fish stay healthy.
- Clownfish secrete a substance that protects them against the sting of sea anemones. They can pass through anemone tentacles, which keeps them safe from predators. Clownfish attract other fish which the anemones can catch and eat.
- When a fruit bat eats the fruit from a fig tree, it eats the seeds as well. These seeds are dispersed through the bat’s droppings.
- Bees gather nectar from flowers, which they make into food. Pollen rubs onto their bodies as they collect the nectar, and the pollen then falls off into the next flower, which pollinates it.
- Humans have a mutualistic relationship with microorganisms, primarily bacteria, in their digestive tract. Bacteria aid in digestion and regulate the intestinal environment, and in return, they feed off of the food humans eat.
Commensalism is a one-sided relationship where one of the organisms benefits greatly from the symbiosis. The other is not helped, but it is not harmed or damaged from the relationship either. In some of these commensalism relationships, the organism that is reaping the benefit will use the other for protection or transportation.
Examples of commensalism in habitats include:
- The cattle egret, a short bird found foraging in cattle herds, eats insects that have been disturbed when the cattle forage. It doesn’t affect the cattle, but the cattle egret depends on this food source.
- A spider uses a tree to build its web. The tree is not impacted but the spider needs the tree for shelter and safety.
- Remora fish, a type of suckerfish, attach themselves to sharks and other large fish. They detach when the larger fish feeds and eat the leftover scraps.
- Tiny pseudoscorpions hitchhike on larger insects to get from place to place. The insect is not harmed, but pseudoscorpions would not be able to travel without this commensalistic relationship.
- Many weeds create spiky burrs that attach to an animal’s hair or fur. As the animal travels, these burrs fall off, successfully dispersing the plant’s seeds.
In parasitism, one organism benefits from the relationship at the expense of the other. The parasitic organism may live inside another organism's body (endoparasitism) or on its surface (ectoparasitism). The host species often weakens and sometimes dies, but in most cases, the parasite needs it to stay alive so it can keep feeding on it.
Examples of parasitic symbiosis include:
- Fleas and mosquitoes feed on blood from other organisms. In this type of parasitic relationship, the host needs to stay alive and it is not damaged greatly.
- Barnacles attach to the bodies of whales. While most whale barnacles have mutualistic relationships with whales, some barnacles slow the whale down while swimming, which does negatively impact the whale.
- Tapeworms live in the small intestines of animals. They eat the animal’s partially digested food, which deprives the host of some food and nourishment.
- Head lice live on small amounts of blood in the scalp. The host human feels itchiness in their hair as the lice bite and move around.
- Parasitoid wasps begin their lives as eggs that are laid in or other living insects. When they hatch, the larvae feed on the body of the other insect until the host insect dies.
Many species compete for the same resources in an ecosystem, which is called competition symbiosis. It may seem like this type of relationship is the opposite of symbiosis, but ecosystems depend on a balance of different species being present. If one species has an abundance of resources and another doesn’t, both species could suffer and possibly die out.
Examples of competition symbiosis include:
- Sea sponges and coral compete for food and marine resources. If the sea sponges have sole access to the resources, they will be successful – but the coral will die. A lack of coral negatively affects the reef, which means that sea sponges could die.
- Jackals and small animals share the same water supply. If the jackals take over a watering hole and restrict other animals from accessing it, the other animals will either die or move to a new location, taking the jackals' food supply with them.
- Both wolves and bears hunt the same prey in their habitats. But if the bears consume all the prey in the area, the wolves will die off, and the habitat will be imbalanced.
Predation and Herbivory
Predation is the process by which one organism feeds on another, typically one animal eating another animal. Herbivory relationships involve an animal eating part or all of a plant.
It may seem like predation is not an example of symbiosis because only one organism survives the encounter. However, without predation, other species would become too numerous and resources would become source. Predatory (or even herbivory) animals never kill every member of the prey species unless the symbiotic relationship is out of balance.
- A lion stalks and kills a gazelle, which makes the herd smaller. The herd now has fewer animals with which to share resources, and each surviving gazelle is stronger as a result.
- Sheep graze on just enough grass to keep themselves fed. Sunlight and water is more evenly distributed through the rest of the grass, allowing it to grow.
- Sea otters eat a variety of sea creatures, including sea stars, clams and octopuses. Each of these animals becomes stronger as a result of predation, which protects them from other animals.
The Circle of Life
Whether it’s a mutually beneficial relationship, a parasitic relationship or a competitive relationship, symbiosis is an important part of our natural world. Without symbiosis in nature, many ecosystems would suffer and cease to flourish. Check out these examples of food chains in different ecosystems to see more about predation relationships. You can also explore heterotroph examples in food chains to learn more about how different organisms sustain themselves.