CBSE Class 7 Answered

Symbiosis is a kind of relationship between two organisms wherein both the organisms are mutually benefited.

Symbiosis occurs in the plants called ‘lichens’. In lichens, the green coloured plant called ‘alga’ (autotroph) and non-green plant 'fungus' (saprophyte) live together. The fungus holds the alga cells in its mat of web-like hyphae (thin filaments). The fungus absorbs the water and mineral salts from the surroundings and supplies them to alga. The alga plant being green prepares the food by photosynthesis and shares it with fungus. Thus, both alga and fungus gain mutually from one another by living together. This is an example of symbiosis.