In nature, most relationships are competitive — one creature trying to eat another, or fighting for the same food or territory. But some species have developed a completely different strategy: working together. When two different species live in a long-term, close relationship that affects both of them, that's called symbiosis.
The three types
Symbiosis isn't always a friendly arrangement. There are three types, depending on who benefits:
- Mutualism — both species benefit. This is the one most people mean when they use the word "symbiosis."
- Commensalism — one species benefits, the other is unaffected.
- Parasitism — one species benefits at the direct expense of the other. Technically a form of symbiosis, even though it doesn't sound much like teamwork.
Classic mutualism: the clownfish and the anemone
You know this one from a certain film. Clownfish live among the tentacles of sea anemones, which would sting and kill most other fish. The clownfish has a special mucus coating that protects it. In return, it chases away fish that would eat the anemone, and its waste provides the anemone with nutrients. Neither harms the other — both gain something useful.
Think of a good business partnership. One person is brilliant at making things, the other is brilliant at selling them. Neither could succeed nearly as well alone. They're not the same company, but they each do better because the other exists. That's mutualism — natural commerce between species.
The most important symbiosis on Earth
The single most important symbiotic relationship is probably the one between plants and the fungi woven through soil, called mycorrhizal fungi. The fungi attach to plant roots and extend their thread-like hyphae much further through the soil than roots can reach, gathering water and minerals. The plant provides the fungi with sugars it can't make itself (fungi can't photosynthesise). This relationship exists in over 80% of all plant species.
Symbiosis inside your own body
You don't have to look far for symbiosis — it's happening right now inside you. Your gut contains trillions of bacteria that help you digest food, produce certain vitamins, and train your immune system. You provide them with warmth and food. They help you function. Without them, you'd be significantly less healthy. You are, in a very real sense, a walking symbiotic ecosystem.
In nature, most animals compete with each other. They fight over food or try to eat one another. But some species have a totally different approach: they work together. When two different species live closely together for a long time, and it affects them both, we call this symbiosis.
The three types
Symbiosis is not always about being friends. There are three different types. Each type depends on who gets something good out of the relationship.
Mutualism means both species benefit. This is what most people think of when they hear the word symbiosis. Commensalism means one species benefits and the other is not affected at all. Parasitism means one species benefits and the other gets harmed. Parasitism is still a type of symbiosis, even though it does not sound like teamwork.
A classic example: the clownfish and the anemone
You probably know this one from a famous film. Clownfish live inside the tentacles of sea anemones. The anemone would sting and kill most other fish. But the clownfish has a special slimy coating that protects it. The clownfish helps the anemone too. It chases away fish that would eat the anemone. Its waste also gives the anemone nutrients to grow. Both creatures gain something useful.
Think of two friends doing a school project together. One is brilliant at drawing the pictures. The other is brilliant at writing the words. Neither could do the project nearly as well alone. They are not the same person, but they both do better because the other is there. That is mutualism.
The most important symbiosis on Earth
The most important symbiotic relationship is probably between plants and fungi. The fungi live in the soil and are called mycorrhizal fungi. They attach to plant roots. They send out tiny thread-like parts, much further into the soil than the roots can reach. These threads collect water and minerals for the plant. The plant gives the fungi sugars in return. Fungi cannot make their own food like plants can. This relationship exists in over 80% of all plant species on Earth.
Symbiosis inside your own body
You do not have to look far to find symbiosis. It is happening inside you right now. Your gut contains trillions of tiny bacteria. They help you digest your food. They help make some vitamins. They also help train your immune system to fight illness. You give the bacteria warmth and food to live on. They help your body work properly. Without them, you would be much less healthy. In a very real sense, your body is a walking symbiosis team.