Overview
This lecture introduces lichens, explaining their structure, mutualistic relationships, adaptations, and ecological significance.
What is Lichen?
- Lichen is a composite organism formed by algae or cyanobacteria living among the filaments of multiple fungi species.
- This relationship between fungi and algae/cyanobacteria is mutualistic, benefiting both organisms.
Structure and Appearance
- Lichens may have tiny leafless branches, flat leaf-like flakes, or a powder-like appearance.
- Lichens lack roots and do not require traditional water reservoirs like plants.
Roles and Mutual Benefits
- Algae or cyanobacteria produce carbon compounds for the fungi via photosynthesis.
- Fungi provide protection, gather moisture, and anchor the algae or cyanobacteria.
Adaptations and Habitat
- Lichens can grow on bare rock, sand, monuments, or as epiphytes on trees.
- They survive extreme drought and thrive in environments unsuitable for most plants.
Ecological Importance
- Lichens cover approximately 6% of Earth's land surface.
- Some lichens are extremely long-lived and considered among the oldest living organisms.
- They are pioneer species, growing first on bare rock after natural disasters like volcanoes.
Key Terms & Definitions
- Lichen — A composite organism from mutualistic association between fungi and algae/cyanobacteria.
- Cyanobacteria — Photosynthetic bacteria, the only prokaryotes capable of photosynthesis.
- Mutualistic relationship — A symbiotic relationship where both organisms benefit.
- Epiphyte — An organism that grows on the surface of a plant.
Action Items / Next Steps
- Review the playlist on lichens and mutualistic relationships for more detailed information.