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#+title: Nature Talk on Lichen

* What is Lichen?
- A plant?
- A fungus?
- An animal?
- Nope!

Lichen is a symbiotic organism made up of a fungus and an algal or cyanobactiral member.

As put by Naturalist and "Lichenologist" Trevor Goward:
#+begin_quote
Lichens are fungi that have discovered agriculture
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* How many lichen are there?
- There are aroun 20,000 known lichen species, but "species" is difficult to define here because most "species" in the rest of the plant and animal worlds are not composed of multiple dependent organisms
- They are usually classified according to their fungus.
- But because lichens are combinations of two (or sometimes even three!) different living organisms, each component has it's own evolutionary and ancestral lineage from each other.
* What types of Lichen are there?
- Fruticose - Tree-like usually with 3-dimensions
  - [[https://www.anbg.gov.au/images/photo_cd/LICHENS_1/image-050_2.jpg][Usnea]]
- Crustose - Stuck hard to a surface and almost impossible to remove with destruction
  - [[https://www.anbg.gov.au/images/photo_cd/LICHENS_1/image-057_2.jpg][Caloplaca]]
- Folisoe - Middle ground between the two, slightly textured, raised off a surface but mostly in 2-dimensions with leaf-like lobes
  - [[https://www.anbg.gov.au/images/photo_cd/LICHENS_2/Image-029_2.jpg][Xanthoparmelia substrigosa]]
* How do they grow?
- They live everywhere that isn't frozen or covered in moving sand dunes
- After a landslide, some of the first living things to appear are alge.
- Many scientists hypothesize that Lichen are among the oldest living things on Earth.
- "Lichenometry" can use the slow growth of lichen and long age to date events based on growth patterns
- Only the fungal partner reproduces, forming discs or bumps that put off spores like other fungi
- After dispersal, fungal spores must meet with compatible algal partners before functional lichen can form
* History
-
- Fossil records are almost non-existant for Lichen.
- [[https://upload.wikimedia.org/wikipedia/commons/thumb/1/17/Rhynie_chert.jpg/300px-Rhynie_chert.jpg][Rhynie chert from Scotland]]
* Resources
- https://en.wikipedia.org/wiki/Symbiosis_in_lichens
- https://www.anbg.gov.au/lichen/what-is-lichen.html
- https://ucmp.berkeley.edu/fungi/lichens/lichens.html
- https://www.livescience.com/55008-lichens.html