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Lichen is a natural indicator of air pollution. Select the correct statement about lichen: A. They show symbiotic relationships B. They are made up of algae and bacteria C. They are natural indicators of SO2 D.  They also help in nitrogen fixation

Lichen is a natural indicator of air pollution. Select the correct statement about lichen: A. They show symbiotic relationships B. They are made up of algae and bacteria C. They are natural indicators of SO2 D.  They also help in nitrogen fixation Correct Answer A and C only

Concept:

  • The term ''Lichen'' was given by Theophrastus.
  • Study of Lichens - Lichenology.
  • Father of Lichenology - Erik acharius

Explanation: 

Lichen:

  • Lichen is a composite thalloid structure of algae & fungi.
  • The algal part of Lichen is called phycobiont and the fungal part is called mycobiont.
  • Both algae & fungi remain in symbiotic association i.e. they are beneficial for each other.
  • The algal component prepares the food by photosynthesis while the fungal component helps in the absorption of minerals and nutrition from the soil
  • Lichens are good indicators of air pollution.
  • Lichens are sensitive towards SO2 (sulphur dioxide). 
  • They die in more concentrations of SO2.
  • Therefore they are not found in those areas (polluted areas) where the concentration of SO2 is high.

Important Points

  • Lichens do not help in nitrogen fixation.
  • Legumes and certain bacteria like Rhizobium help in nitrogen fixation.​

Thus,

A. They show symbiotic relationships: Correct

B. They are made up of algae and bacteria: Incorrect

C. They are natural indicators of SO2: Correct

D.  They also help in nitrogen fixation: Incorrect

Additional Information

Other ecological importance of Lichen:

  • Many Lichens are used as food and fodder. Eg –Parmelia, used as food in South India. It is known as Rock Flower.
  • It is also used as dyes. Eg – Litmus(Acid-base indicator) is obtained from many members of lichens like Roccella tinctoria.
  • The crustose and foliose lichens grow on rocks and secrete different types of acids. These acids break the rocks. In this way, these lichens help in soil formation.

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