What are lichens? Explain its characteristics.

Lichens are organisms formed by the symbiotic association of algae and fungi. They are unique because two different organisms live together and benefit each other.

Characteristics of Lichens:

• Dual Organism: A lichen is made of a fungus (provides structure and protection) and algae or cyanobacteria (performs photosynthesis).
• Symbiotic Relationship: Algae prepare food through photosynthesis, while fungi absorb water and minerals from the environment.
• Growth Forms: Lichens exist in crustose (crust-like), foliose (leafy), and fruticose (shrubby) forms.
• Habitat: They grow in extreme conditions such as rocks, tree bark, deserts, and mountains.
• Indicator Species: Lichens are sensitive to pollution, especially sulfur dioxide, and are used to check air quality.
• Slow Growth: Lichens grow very slowly and can live for hundreds of years.
• Reproduction: They reproduce through fragmentation, soredia, or isidia.