Endosymbiosis facts for kids
Endosymbiosis occurs when a symbiont (bacteria, fungi, lichen, etc.) lives inside the body or the cells of another organism. It is a very widespread phenomenon in living things.
The term endosymbiosis is from the Greek: ἔνδον endon "within", σύν syn "together" and βίωσις biosis "living".
Sometimes organims mutually benefit from endosymbiosis. For example, gutless marine worms of the genus Riftia' get nutrition from their endosymbiotic bacteria. This endosymbiosis is obligate; that is, either the endosymbiont or the host cannot survive without the other. However, some endosymbioses can be harmful to either of the organisms involved.
Examples of endosymbiosis
- Rhizobia: nitrogen-fixing bacteria which live in root nodules on plants of the pea family.
- Singly-celled forams which include a single-celled alga inside the cell. This is 'facultative', which means they may or may not do it. A more far-reaching version is idioplastic endosymbiosis. Here, the foram consumes the alga, but keeps its chloroplasts in working order.
- Green algae inside marine polychaete worms.
- Single-celled algae inside reef-building corals.
- Gut flora (often flagellates) inside the digestive systems of insects and vertebrates which digest plant cellulose. These are 'obligate' symbionts, which means the host must have them.
- Lichen: fungus+alga or bacterium.
- Mycorrhiza: fungal hyphae and roots of trees.
Images for kids
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A representation of the endosymbiotic theory
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Diagram of cospeciation, where parasites or endosymbionts speciate or branch alongside their hosts. This process is more common in hosts with primary endosymbionts.
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Pea aphids are commonly infested by parasitic wasps. Their secondary endosymbionts attack the infesting parasitoid wasp larvae promoting the survival of both the aphid host and its endosymbionts.
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See also
In Spanish: Endosimbionte para niños
