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Class 12th Biology 2013 Set1 Delhi Board Paper Solution

Question 27

Explain mutualism with the help of any two examples. How is it different from commensalism?

Mutalism is the interaction which confers benefits on both the interacting species. Lichens represent an intimate mutualistic relationship between a fungus and photosynthesising algae or cynobacteria. Similarly, the mycorrhizae are associations between fungi and roots of higher plants. Fungi help the plant in the absorption of essential nutrients from the soil while the plant in turn provides the fungi with energy yielding carbohydrates. 
• The interaction where one species is benefitted and the other is neither benefitted nor harmed is called commensalism.
Species            Species                 Name of interaction
A                             B
+                             +                            Mutualism
+                             0                            Commensalism