I'M LICHEN IT!

Lichen are mutualists.  It's a combination critter being basically a fungus with an alga living within it....one a consumer (fungus) the other a producer (alga).

This combination allows them to colonize many unusual places...they work together to make a living (someone should tell the Congress). They can even colonize solid rock...the fungus provides water, minerals and living space...the alga (singular of algae) can photosynthesize and provide sugars for energy. Neither can survive the rock without the other.
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I've Blipped before about lichen noting that there are several iterations but all of them are simply lichen/alga partners. All that differs is form (structure) and basic habitat.
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For those who can't live without color, check the Extra.
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Best in Large.