Which organisms are involved in the close mutualistic relationship found in lichens?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Fungus and photosynthesising algae or cyanobacteria
In mutualism, both partners benefit. A lichen is a close mutualistic partnership between a fungus and a photosynthesising partner, either an alga or a cyanobacterium. The alga or cyanobacterium makes food by photosynthesis. The fungus gives shelter and absorbs water and minerals. Together they can live on bare rocks and tree bark.
Option (1) Fungus and roots of higher plants — Incorrect. A fungus with the roots of higher plants is a mycorrhiza. It is also mutualism, but it is not a lichen. The fungus helps the plant absorb nutrients, and the plant gives the fungus carbohydrates.
Option (2) Fungus and photosynthesising algae or cyanobacteria — Correct. A lichen is formed by a fungus and photosynthesising algae or cyanobacteria.
Option (3) Fungus and archaebacteria — Incorrect. Archaebacteria are ancient bacteria that live in extreme places such as hot springs and salty areas. They are not partners in lichens.
Option (4) Fungus and protozoa — Incorrect. Protozoa are single-celled animal-like organisms. They cannot photosynthesise, so they cannot supply food to the fungus. A lichen needs a photosynthetic partner.
NCERT Extract:
Population Interactions – “… (v) Mutualism: This interaction confers benefits on both the interacting species. Lichens represent an intimate mutualistic relationship between a fungus and photosynthesising algae or cyanobacteria. Similarly, the mycorrhizae are associations between fungi and the roots of higher plants. The 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.”