Previous Year Question
In the nature, which of the following is/are most likely to be found surviving on a surface without soil?
Fern
Lichen
Moss
Mushroom
Select the correct answer using the codes given below.
1 and 4
Only 2
2 and 3
1, 3 and 4
Correct Answer: C
Detailed Solution
Lichens and mosses can survive without soil on rocks, tree bark and other surfaces.
A lichen is a symbiotic association between a fungus and a photosynthetic alga or cyanobacterium.
Its fungal component helps provide shelter, water and minerals, whereas the photosynthetic component produces food.
A lichen has no true roots and can obtain water and nutrients from rainfall, air and dust.
It can tolerate desiccation and become active again when favourable conditions return.
Therefore, lichens are among the pioneer organisms of primary succession on bare rocks and hard surfaces.
Lichens also contribute to the weathering of rocks and the initial formation of soil.
Moss is a non-vascular plant belonging to the bryophyte group and possesses thread-like rhizoids instead of true roots.
Rhizoids anchor moss to a surface, while water and nutrients are mainly absorbed through its body surface.
Therefore, moss can grow on moist rocks, tree trunks and soil-free surfaces.
A fern is a vascular plant with true roots, stems and leaves; it generally requires soil or a suitable organic substrate.
Some ferns may be epiphytic, but among the given options, lichens and mosses are most commonly likely to survive on soil-free surfaces.
A mushroom is the fruiting body of a fungus and requires soil, decaying wood or another organic substrate for nutrition.
Therefore, fern and mushroom are not the appropriate answers to this question.