Question

With respect to the given assertion and reason, choose the right option

Assertion [A]: Lichens are the primary colonizers of bare rocks.
Reason [R]: Lichens are called pioneer organisms.

• A. Both A and R are true and R explains A
• B. Both A and R are true but R does not explain A
• C. A is true and R is false
• D. Both A and R are false

Answer 1

The correct option is A

Both A and R are true and R explains A

The initiation of ecological succession on a bare rock requires a pioneer organism like lichens which facilitate a suitable environment for the successful colonization of other organisms. The acidic secretions from the lichens break down the substrate and add to the accumulation of soil. Mosses then colonize the soil, adding enough nutrients in the soil for alder shrubs to take hold. Over maybe a hundred years, alders build up the soil nitrogen levels until spruces are able to thrive, eventually crowding out the alder and forming a dense spruce forest. Lichens are not only found as pioneer species but can also luxuriantly grow on the barks or any other moist areas throughout the world. Since the tropics are relatively more humid, lichens grow luxuriantly in the tropical regions.