Fungi
 What are fungi?
 Fungi are eukaryotic heterotrophs that have cell walls made of chitin (a complex carbohydrate)
 Nutrition: fungi obtain their food by absorption. Can be
 Saprobes-eat dead matter
 Parasites- harm “partner” (parasitic fungi can be detrimental to health, agriculture)
 Symbionts-relationship beneficial to both partners
 Structure
 Fungi are multicellular except for yeasts which are unicellular
 Fungi are composed of filaments called hyphae
 Each hyphae is one cell thick
 Hyphae woven together are called a mycelium (The mycelium is a “web” of hyphae)
 Mycelium- the “body” of the fungus. Typically it is found underground
 Fruiting bodyo The part of the Fungi that sticks out of the mycelium-above ground and is actually the fungi’s reproductive
structure
 Reproduction
 Fungal gametes are very similar which is why fungi are not designated male or female but + or –
 Most Fungi reproduce sexually with the release of pheromones as a signal, or asexually
 Fungi can reproduce asexually by having a piece of hyphae break off and start growing elsewhere- (budding)
 The most common way for Fungi to reproduce asexually us by releasing spores
 Spores are produces in structures called sporangia
 “Puffball” fungi may release over a billion spores in one puff. There is less than a one in a billion chance that a
spore will find a hospitable environment to land in.
 Mushrooms hold their spores in the “cap” or underside of the fruiting body
 Spore Dispersal
 Fungi are immobile so they rely on a variety of means for spore dispersal
o Wind: Spore are light and numerous, there is safety in numbers
o Animals-stick to fur, being ingested
 Sexual Reproduction
 In addition to reproducing asexually, Fungi reproduce sexually, which increases genetic variation
o Variation contributes to natural selection. Individual variations among offspring will contribute to
adaptation in changing environments.
 Classification—a work in progress
 Fungi can be classified into four groups
o Chytrids: Unique among fungi in that they have flagellated spores, called zoospores
o Zygomycota
o Ascomycota
o Basidiomycota
 Zygomycota
 “common molds”
 Famous zygomycete: Rhizopus stolinofer- bread mold
 Produced extensive masses of threadlike structures called hyphae that spread out over the food, penetrate it,
and absorb nutrients
 Ascomycota
 “Sac Fungi”
 Yeasts, truffles, morels
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Ascomycete Reproduction
 Ascomycetes reproduce asexually by producing vast numbers of asexual spores called conidia, though
yeasts reproduce by budding instead of spores
 Ascomycetes reproduce sexually by producing sexual spores in saclike asci (singular: ascus)
o Yeasts
 Only unicellular Fungi
 Parasite “yeast infection”
 Baking
 Fermentation
 Pink film or shower curtain
o Truffles
 Tuber melanosporum is highly prized for its flavor by gourmet cooks who will pay over $600 per
pound
Basidiomycota
 Club fungi
 Mushrooms we eat: really basidiocarps (fruiting body)
 25,000 species identified
 Very talented decomposers
o Club fungi
 Basidia are found on the mushroom gills: source of basidiospores
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 Each common store bought mushroom contains about 200cm of surface area to store basidiospores
 In one release a billion spores can be dropped and blown away
FYI: Deuteromycota
 Imperfect fungi
o Classified into this division because scientists have not been able to determine their mode of
reproduction- moved as they do.
 Penicillin- famous imperfect fungi
Ecology
 Important role of fungi in an ecosystem= to break down dead organisms
 Saprobes
o Eat decaying organic matter- decomposers
 Some environments are so rich in fungal spores that as soon as a leaf falls or an insect dies it is instantaneously
covered in spores
 Many saprobes work with bacteria, and protists in the process of decomposition
 Fungi from symbiotic relationships (work mutually) with plants, algae, cyanobacteria, and animals.
o Mycorrhizae- plant roots + fungi example: orchids cannot germinate without symbiotic relationship with
certain fungi
o Lichens- photosynthetic microorganisms + fungi
Lichens
 Lichens are resistant to drought and cold because of the relationship they have with green algae or cyanobacteria
 The green algae or cyanobacteria provides the fungus with the products of photosynthesis
 The fungus provides its partner with water and minerals that it collects from the surface of where it is growing
 Lichens are important in succession
 Lichens can be used as an indicator of air quality