What
are fungi?
Singular
= FUNGUS
Plural
= FUNGI
A
fungus is ...
Fungi
are...
Origin of word fungus
Two schools of thought:
sp(h)ongos - Greek
= sponge-like
fungor - Latin
=
to fluorish
Both words probably relate to nature of fungal
structures we call mushrooms or toadstools
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Definition
of Fungi
Eucaryotic, heterotrophic and absorptive organisms,
which have cell walls, typically reproduce
asexually and/or sexually by producing spores,
and grow either reproductively by budding or
nonreproductively by hyphal tip elongation.
Definition excludes:
1. bacteria & blue-green algae (prokaryotes)
2. slime molds
3. true algae & higher plants
4. animals
5. etc.
Definition may include some non-fungi
1. Oomycetes (water molds)
2. etc.
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No
perfect definition
1. Fungi historically have represented a very
heterogenous grouping of unrelated or only
distantly related organisms.
2. Adaptation of related or unrelated
fungi or fungal-like organisms to similar
ecological niches have led to structural trends
that obscured fungal origins (phylogeny*)
* Phylogeny = evolutionary history of genetically
related organisms
A. Monophyletic - one origin
B. Polyphyletic - multiple origins
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Trends
in evolution that
tended to obscure fungal nature
(phylogeny)
1. Convergent Evolution
unrelated organisms superficially come to look
alike
e.g. some fungi and colorless algae
2. Parallel Evolution
members of unrelated groups evolve along similar
paths
e.g. some fungi and animals, like slime molds
3. Divergent Evolution
Related organisms come to have very different
biology - they took different paths of evolution
(adaptation)
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Fungal nutritional types
1. Saprophytes
2. Symbionts
a. mycothallal fungi
e.g. lichens
b. mycorrhizal fungi
- ectomycorrhizal = can be free-living
- endomycorrhizal = obligate symbionts
c. animal-fungal partners
e.g. gut fungi
3. Pathogens
a. majority plant pathogens
b. many animal pathogens
c. relatively few but increasing # of human
pathogens
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