Chapter 20, Problem 31A

Summary Introduction

Introduction :

Lichen is known as a symbiotic relationship between an alga or a photosynthetic host and the fungi. Usually the fungus is an ascomycete but basidiomycetes can also be found in lichens. The photosynthetic host is either a green algae or a cyanobacterium that supplies food to both animals.

Answer to Problem 31A

Correct answer :

The correct answer is option (d) They are susceptible to air pollutants

Explanation of Solution

Explanation/justification for the correct answer :

Option (d) they are susceptible to air pollutants. Lichen as bioindicators are particularly resistant to toxins from the atmosphere, because they eat all of their soil and rain water and minerals. A bioindicator is a living organism that is prone to changing environmental factors to respond to changing circumstances. So, the correct answer is option (d).

Explanation for incorrect answer :

Option (a) they are susceptible to drought. Lichen survives extreme drought. They are drying out, preventing photosynthesis and becoming brittle. Once water is available again, the lichens rapidly drink vast quantities of water and begin the photosynthesis cycle. So, this is an incorrect answer.

Option (b) they are unicellular. Single-celled spores, or unicellular, are named yeasts. Yeasts are present worldwide in soils, on plant surfaces and also in human bodies. So, this is an incorrect answer.

Option (c) They are mutualistic. Lichen is an example of shared connections between the fungi and other species. So, this is an incorrect answer.