Question

Association in a lichen is
A. Temporary
B. Parasitic
C. Permanent
D. Obligatory

Answer 1

Hint: It is a type of symbiotic relationship between two distantly related species. This association is an association in which neither organisms can survive if they are separated. It is hard to differentiate between the two organisms.

Complete step by step answer: Lichens form a mutually beneficial association between fungus and algae. The fungal partner is known as mycobiont, whereas, the algal partner is known as phycobiont. Ascomycetes usually act as a mycobiont whereas green algae act as a phycobiont species. Lichens are known as pioneer organisms in the biological succession. They can grow in extremely inhospitable conditions. They are also known as an indicator of pollution or indicator organisms because they cannot grow in presence of sulfur dioxide. Mycobiont help in providing structure and helps in anchorage and absorption of water and minerals, while, Phycobiont helps in the process of photosynthesis and provide food to the fungal partner. It is a type of symbiotic association and it is an obligatory relationship in which both the partners are benefitted. Common examples of lichens are Cladonia (Reindeer lichen), Evernia (Oakmoss), Cetraria (Iceland moss), etc.
Hence, the correct answer is option D.

Note: The vegetative portion of lichens is known as thallus. The thallus gives its characteristic outer appearance. Thalli can have different forms. The mycobiont and phycobiont are arranged in different layers. In case of an algal or cyanobacterial partner, they are arrangements in form of small compartments in the upper cortex.