CBSE Class 9 Answered
Symbiotic nutrition or symbiosis is a mode of nutrition in which two types of organisms live together, exchange nutrients and are mutually benefited. One of the organisms provides nutrients required by the other organism while the other provides shelter or nutrients or both. The organisms which provide nutrients required by the other organism and obtain shelter or nutrients or both in return are called symbiotic organisms or symbionts.
Lichens show symbiotic association of entirely two different plants, the alga, which is an autotroph and fungi, which is a saprophyte. In symbiosis, the fungus absorbs water, minerals and salts and provides protection to the alga. The alga being green, utilizes the water supplied by the fungus during symbiosis, to prepare the food during photosynthesis. This food is then made available to the fungus for its growth.