Lichen

Definition

Lichen is a complex symbiotic organism formed from the association between a fungus and a photosynthetic partner, usually an alga or cyanobacterium. This unique partnership allows lichens to thrive in various environments, making them important indicators of ecosystem health and functioning in terrestrial biomes. Their ability to survive in extreme conditions and contribute to soil formation highlights their ecological significance.

5 Must Know Facts For Your Next Test

1. Lichens can be found in a wide range of terrestrial biomes, including deserts, tundras, forests, and mountains, demonstrating their adaptability to harsh conditions.
2. They play a crucial role in soil formation by breaking down rock surfaces and contributing organic matter as they grow and die.
3. Lichens are sensitive to air pollution, particularly sulfur dioxide, making them valuable bioindicators for monitoring environmental health.
4. They reproduce through spores produced by the fungal partner or through vegetative means such as fragmentation or the production of soredia.
5. Some lichens can withstand extreme temperatures, dehydration, and even radiation, showcasing their resilience and importance in understanding ecosystem dynamics.

Review Questions

• How do lichens demonstrate symbiosis between fungi and photosynthetic partners?
  • Lichens exemplify symbiosis through the relationship between mycobionts (fungi) and photobionts (photosynthetic partners). The fungus provides structure, protection, and moisture retention for the photosynthetic partner, while the photobiont produces organic compounds through photosynthesis that nourish both organisms. This mutualistic relationship enables lichens to thrive in diverse environments where individual organisms may struggle to survive.
• Discuss the ecological roles of lichens in terrestrial biomes and their significance as bioindicators.
  • Lichens serve several ecological roles in terrestrial biomes; they contribute to soil formation by breaking down rock surfaces and adding organic matter. Additionally, their sensitivity to air pollution makes them significant bioindicators. The presence or absence of certain lichen species can indicate the health of an ecosystem and levels of air quality, helping scientists monitor environmental changes and the impacts of human activities.
• Evaluate how lichens' resilience contributes to ecosystem stability and their ability to adapt to changing environments.
  • Lichens exhibit remarkable resilience due to their ability to withstand extreme temperatures, dehydration, and radiation. This resilience allows them to colonize inhospitable areas, contributing to ecosystem stability by facilitating soil development and providing habitats for other organisms. As climate change alters environments, lichens' adaptability may help maintain ecosystem functions by supporting nutrient cycling and serving as pioneer species in succession processes.

Related terms

Symbiosis:

A close and often long-term interaction between two different biological species, which can be mutualistic, commensalistic, or parasitic.

Mycobiont: The fungal component of a lichen that provides structure, protection, and moisture retention for the symbiotic relationship.

Photobiont: The photosynthetic partner in a lichen, typically an alga or cyanobacterium, which produces organic compounds through photosynthesis that nourish the lichen.