Symbiosis facts for kids
Symbiosis means "living together." It describes a close and long-term relationship between two different species. In these relationships, at least one of the species gets a benefit. The word was first used by scientists like Anton de Bary in 1879 to mean "the living together of unlike organisms."
An organism living in a symbiotic relationship is called a symbiont. If one species lives inside another, like tiny organisms living inside the cells of a host, it's called an endosymbiont.
Symbiosis is very common and important for how life on Earth has evolved. Most plants and animals have symbionts. These tiny partners are often crucial for the larger organisms to survive. For example, special fungi called Mycorrhiza help plants, and gut flora (good bacteria) help insects and vertebrates digest food. Humans also rely on many helpful bacteria inside their bodies.
Many symbiotic relationships are between organisms from completely different kingdoms. Even the eukaryote cells that make up all animals and plants contain tiny parts called organelles. These organelles, like mitochondria and plastids, are actually descendants of ancient symbiotic bacteria that started living inside other cells billions of years ago. This shows how important symbiosis has been in the history of life.
Contents
What is Symbiosis?
Symbiosis is a broad term for different ways species interact over a long time. It includes relationships where:
- One organism benefits and the other is harmed (like parasitism).
- Both organisms benefit (called mutualism).
- One organism benefits and the other is not affected (called commensalism).
- Both organisms are harmed (called competition).
Different Kinds of Symbiosis
Symbiotic relationships can be grouped into different types based on how the partners affect each other.
When Partners Stay Separate
In these types of symbiosis, the organisms live close to each other but keep their bodies separate.
- Parasitism: One partner benefits, and the other is harmed. Sometimes, the parasite can even kill its host. (One wins, one loses: + –)
- Mutualism: Both partners benefit from the relationship. (Both win: + +)
- Commensalism: One partner benefits, but the other is not helped or harmed. (One wins, one is neutral: + 0)
- Competition: Both partners are fighting for the same resources, like food or space. This harms both of them. (Both lose: – –)
When Partners Live as One Organism
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This type of symbiosis is called endosymbiosis, where one organism lives inside the other.
- Rhizobia: These are nitrogen-fixing bacteria that live in special bumps (nodules) on the roots of plants like peas. They help the plant get nitrogen from the air.
- Lichen: A lichen looks like a single organism, but it's actually a close partnership between a fungus and an alga (or a bacterium). The alga lives inside the fungus. The fungus needs the alga to survive, but the alga can live on its own.
- Mycorrhiza: This is a partnership between fungi and the roots of trees. The fungal threads (hyphae) help the tree get water and nutrients, and the tree provides food for the fungus.
- Bacteria in guts: Many insects and vertebrates (like cows or termites) have bacteria in their guts that help them digest plant material like cellulose. Animals usually can't break down cellulose on their own, so these bacteria are essential.
- Cells of all animals and plants: Scientists believe that the eukaryote cell (the type of cell all animals and plants are made of) evolved from ancient endosymbiosis. Tiny parts inside these cells, like mitochondria and chloroplasts, have their own DNA. This DNA is a leftover from when they were once separate bacteria that started living inside other cells.
Cool Examples of Symbiosis
Here are some amazing examples of symbiosis in nature:
- Clownfish and Sea Anemones: This is a great example of mutualism. Clownfish live safely among the stinging tentacles of tropical sea anemones. The clownfish is protected from predators because it has a special mucus that stops the anemone's stings. In return, the clownfish protects the anemone from other fish that might eat it. Clownfish waste also provides nutrients, and they can even help the anemone get more oxygen at night!
- Goby Fish and Shrimp: This is another mutualistic partnership. A goby fish and a shrimp often share a burrow in the sand. The shrimp digs and cleans the burrow, but it's almost blind and vulnerable to predators when outside. The goby fish acts as a lookout. If a predator comes near, the goby touches the shrimp with its tail. This signal tells both of them to quickly hide in the burrow.
- Ants and Aphids: Some species of ants act like farmers! They "farm" aphids. The ants protect the aphids from predators and even move them to better feeding spots. In return, the ants get a sweet, sticky fluid called honeydew that the aphids secrete after sucking sap from plants.
- Herbivores and Gut Bacteria: Many plant-eating animals, or herbivores, have special bacteria living in their guts. These bacteria help them digest plant material, especially cellulose, which makes up plant cell walls. Most animals can't digest cellulose on their own, so these bacteria are essential for them to get energy from plants.
Images for kids
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In a symbiotic mutualistic relationship, the clownfish feeds on small invertebrates that otherwise have potential to harm the sea anemone, and the fecal matter from the clownfish provides nutrients to the sea anemone. The clownfish is additionally protected from predators by the anemone's stinging cells, to which the clownfish is immune. The clownfish also emits a high pitched sound that deters butterfly fish, which would otherwise eat the anemone.
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Alder tree root nodule
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Hermit crab, Calcinus laevimanus, with sea anemone.
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Bryoliths document a mutualistic symbiosis between a hermit crab and encrusting bryozoans; Banc d'Arguin, Mauritania
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Phoretic mites on a fly (Pseudolynchia canariensis).
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Flea bites on a human is an example of parasitism.
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See also
In Spanish: Simbiosis para niños
