Question

Which of the following would appear as the pioneer organisms on bare rocks?
A. Lichens
B. Liverworts
C. Mosses
D. Green algae

Answer 1

Hint: It is a composite organism that appears in a mutualistic relationship of algae or cyanobacteria living within filaments of multiple species of fungi.

Complete Answer:
Pioneer species are those which are among a new site's first arrivals. In primary succession, they are usually active. For later animals, they perform the unique service of planning a habitat. The pioneering organisms have a high dispersion rate that makes them more likely to enter the new habitat. Pioneer species are named the species that enter a barren area.

Now, let us find the solution from the options-
- Lichens are called pioneers because the rock and ash producing soil will begin to be depleted. They can survive because they live in a relationship between a fungus and an algae that is mutualistic. Other species, bacteria, fungi, various grasses, etc., will emerge after these lichens have completed their job. This is called ecological succession. Lichens in primary succession on rocks are able to secrete acids to melt rock, aiding in weathering and soil formation.
- Liverwort is a small, flowerless green plant that occurs in damp environments such as damp rock or moist soil with leaf-like stems or lobed leaves. True roots are absent in liverworts and replicate from capsules by means of spores released. They are not considered as pioneer organisms. Thus, the option B is incorrect.
- Mosses are avascular, small, spore-bearing plants of the Bryophyta division. Mosses are found on wet city streets, and on roofs, in cracks between paving stones. They are not considered as pioneer organisms. Thus, the option C is incorrect.
- Green algae can be grown on land, often on rocks and trees, some of which occur on the snow surface. They are predominant in areas where light, like shallow water and tide pools, is plentiful. Green algae does not serve as pioneer organisms Thus, the option D is incorrect.

Thus, the correct answer is option A Lichens.

Note: In colonisation, mosses typically follow lichens, but cannot act as pioneer species. Pioneer species change their habitat and build opportunities for other species to tolerate them. Some species may be called pioneer species in certain cases. Typically, birds are the first to inhabit newly formed islands.