Question

Is lichen a symbiotic relationship?

Answer 1

Lichens consist of two or more closely interacting organisms, a fungus, and one or more photobiont partners. An alga and/or cyanobacteria, both of which can make simple sugars through photosynthesis, could constitute the photobiont. Fungi, on the other hand, are 'heterotrophic,' meaning they require sustenance from outside sources. The fungus constructs the lichen thallus, within which they create the circumstances for a long-term, stable relationship with their photobionts, which is the foundation of the lichen symbiosis.

Complete answer:
Yes, a lichen is a durable symbiotic relationship between a fungus, algae, and/or cyanobacteria.

Lichen fungi, like all fungi, require carbon as a food supply, which is given by photosynthetic parasitic algae and/or cyanobacteria. Because both the fungi and the photosynthetic partners, known as photobionts, benefit from the lichen symbiosis, it is regarded to be a mutualism.

Lichens are symbiotic relationships between fungus (mycobionts, such as Ascomycetes) and photosynthetic partners (photobionts), such as green algae or diazotrophic cyanobacteria (commonly Nostoc spp.)

The mutually beneficial symbiotic interaction of green algae and/or blue-green algae (cyanobacteria) dwelling among filaments of a fungus, generating lichen, is known as lichen symbiosis. Living as a symbiont in a lichen appears to be an effective strategy for a fungus to obtain critical nutrients, as it is found in roughly 20% of all fungal species. The autotrophic symbionts found in lichens include a wide range of basic photosynthetic organisms that are generally referred to as "algae." Both prokaryotic and eukaryotic species have symbionts.

Note:
Lichen fungi have developed multiple times independently inside the mushroom-forming fungi and their relatives (the basidiomycetes), but most typically from within the cup mushrooms (the ascomycetes). Cup fungus account for nearly all of the familiar and colourful crusts, rosette-forming, foliose (leafy) forms, and shrubby or fruticose lichens that many people are familiar with.