Correct Option
The correct option is Rhizobium – Symbiotic relationship
Explanation
Organisms acquire nutrients through specific modes of nutrition, such as autotrophic, heterotrophic, or saprotrophic. Furthermore, distinct biological interactions define how organisms coexist, such as symbiosis (mutual benefit) or parasitism (benefit to one at the expense of the other).
Option Analysis
- Option (a) is Incorrect: Lichens represent a symbiotic relationship (mutualism) between an algal component (phycobiont) and a fungal component (mycobiont). The algae provide food via photosynthesis, while the fungi provide shelter and absorb water and minerals. It is not a parasitic relationship.
- Option (b) is Correct: Rhizobium bacteria reside in the root nodules of leguminous plants. The bacteria fix atmospheric nitrogen into soluble forms for the plant, and in return, the plant provides food and shelter. This mutually beneficial association is a symbiotic relationship.
- Option (c) is Incorrect: The Pitcher plant is an insectivorous plant. It performs photosynthesis (autotrophic) but traps insects to fulfill its nitrogen requirements in nitrogen-deficient soils. It is not saprotrophic, as saprotrophs feed on dead and decaying organic matter.
- Option (d) is Incorrect: Mushrooms are fungi that lack chlorophyll and cannot perform photosynthesis. Therefore, they are not autotrophic. They exhibit saprotrophic nutrition, deriving nutrients by decomposing dead organic matter.
Key Takeaway
Symbiosis is a close association where both organisms benefit (e.g., Rhizobium and legumes). Saprotrophic nutrition involves feeding on dead and decaying matter (e.g., Fungi), whereas Insectivorous plants are partial heterotrophs adapted to nitrogen-deficient soils.