Which of the following statements regarding lichens is FALSE?
A) Lichens are a mutualistic relationship between a fungus and a protozoan. B) Lichens represent a mutualistic relationship between a fungus and an alga. C) Lichens are often the first life form to colonize rock or soil. D) The algal partner produces carbohydrates that are absorbed by the fungal partner. E) The fungal partner provides a means of attachment and protects the algal partner from desiccation.
The correct answer and explanation is:
The correct answer is A) Lichens are a mutualistic relationship between a fungus and a protozoan.
Explanation:
Lichens are a fascinating example of mutualistic symbiosis, where two distinct organisms form a partnership for their mutual benefit. In a lichen, the two main partners involved are a fungus and an alga (or sometimes a cyanobacterium), not a protozoan. Here’s a breakdown of the key components and functions:
- Fungus and Alga (or Cyanobacterium):
The primary relationship in a lichen is between a fungus and an alga or sometimes a cyanobacterium. The fungus provides the structure and support for the lichen, forming a protective layer around the photosynthetic partner. The alga or cyanobacterium, on the other hand, conducts photosynthesis to produce carbohydrates, which nourish both itself and the fungus. - Lichens as Pioneer Species:
One of the critical roles of lichens in ecosystems is their ability to colonize barren or inhospitable environments like rocks and soil that lack vegetation. Because they can thrive in extreme conditions, lichens are often the first organisms to establish life on surfaces that are initially devoid of life, contributing to the gradual process of soil formation. - Mutualistic Benefits:
- The fungal partner provides a safe environment for the alga or cyanobacterium, helping it attach to surfaces and protecting it from desiccation (drying out) and harsh conditions like UV radiation.
- The algal partner, through photosynthesis, produces carbohydrates that nourish the fungus. The fungus can absorb these sugars and, in return, helps the alga access moisture and minerals.
Why Option A is False:
The term “protozoan” in option A is incorrect. Lichens do not involve a partnership with protozoans. Protozoans are a group of single-celled eukaryotic organisms, which typically do not play a role in lichen symbiosis. The correct symbiotic partners in lichens are a fungus and an alga or cyanobacterium, as explained above.
Thus, the other statements (B, C, D, E) are true, as they correctly describe the mutualistic nature of lichens, their role as pioneer species, and the beneficial exchange between the fungal and algal partners.