Symbiosis
Understand symbiosis (close relationships between different species), including mutualism (both benefit, like clownfish and anemones), commensalism (one benefits without harming the other, like remora fish riding sharks), and parasitism (one benefits at the other's expense, like ticks on deer), and recognise these relationships in nature
What a learner can do afterwards
- Defines symbiosis as a close relationship between different species
- Distinguishes mutualism, commensalism, and parasitism with an example of each
- Identifies symbiotic relationships when presented with new scenarios
1 · Read
Symbiosis is a close relationship between two different kinds of living things. The two species live near each other, and their lives affect one another. Scientists sort these relationships into three types, based on who benefits and who does not.
Take clownfish and sea anemones. The clownfish swims safely inside the anemone's stinging tentacles, protected from other fish. In return, the clownfish cleans the anemone and chases off fish that might eat it. Both animals benefit, so this is called mutualism.
Now think about a remora fish riding along on a shark's body. The remora eats scraps of food the shark leaves behind and gets a free ride to new hunting grounds. The shark is not helped or harmed. Only the remora benefits, so this is called commensalism.
A tick on a deer's skin tells a different story. The tick feeds on the deer's blood and grows fatter, while the deer loses blood and can get sick. The tick benefits, but the deer is harmed. This is called parasitism.
To work out which type of symbiosis you are looking at, ask two questions: does each animal benefit, and is either animal harmed? Both benefit means mutualism, one benefits with no harm means commensalism, and one benefits while the other is harmed means parasitism.
Symbiosis is a close relationship between species: mutualism helps both, commensalism helps one without harming the other, and parasitism helps one while harming the other.
More to read
Symbiotic relationships within ecosystems
Symbiosis means a close link between two kinds of living things. They share a life for a long time. At times both sides win. At times just one side wins.
Bees sip sweet juice from blooms. Blooms get their dust moved plant to plant. Both sides win. That fair deal is called mutualism.
24.4 Fungal Parasites and Pathogens
Some fungi feed on other living things. They rob food from plants and beasts. The host grows sick. The thief grows strong.
This unfair link is called parasitism. One side wins while one side loses.
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2 · Watch
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Where it sits
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Optional connections
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Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
24 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.