lichen growing on trees in Great Otway National Park, Victoria, Australia
Contributor:B.O'Kane / Alamy Stock Photo
File size:24.1 MB (2.1 MB Compressed download)
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Dimensions:2370 x 3554 px | 20.1 x 30.1 cm | 7.9 x 11.8 inches | 300dpi
Date taken:5 November 2011
Location:Great Otway National Park, Victoria, Australia
Lichens are composite organisms consisting of a symbiotic relationship between a fungus (the mycobiont) and a photosynthetic partner (the photobiont or phycobiont), usually either a green alga (commonly Trebouxia) or cyanobacterium (commonly Nostoc). Lichens occur in some of the most extreme environments on Earth—arctic tundra, hot deserts, rocky coasts, and toxic slag heaps. However, they are also abundant as epiphytes on leaves and branches in rain forests and temperate woodland, on bare rock, including walls and gravestones, and on exposed soil surfaces (e.g., Collema) in otherwise mesic habitats.