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Fungi
Chapter 31
Defining Fungi
Mycologists believe there may be as many
as 1.5 million fungal species
Fungi are classified into six main groups
-Chytrids
-Zygomycetes
-Glomeromycetes
-Ascomycetes
-Basidiomycetes
-Deuteromycetes
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Defining Fungi
Fungi share the following characteristics
1. Are heterotrophs that absorb nutrients
2. Have a number of different cell types
3. Have cell walls that include chitin
4. Some have a dikaryon stage
5. Undergo nuclear mitosis
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General Structure of the Fungi
Multicellular fungi consist of long, slender
filaments called hyphae
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General Structure of the Fungi
A mass of connected hyphae is called a
mycelium
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General Structure of the Fungi
Cells walls of fungi are formed of
polysaccharides including chitin
-Cross-linked with proteins
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Haploid? Diploid?
Hyphae may have more than one nucleus
-Monokaryotic – One nucleus
-Dikaryotic – Two nuclei
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Mitosis
Fungi have an unusual mitosis
-Nucleus does not break down and reform
-Instead, they form the spindle apparatus
within the nucleus
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Reproduction
Fungi can reproduce sexually and asexually
Sexual reproduction involves the fusion of two
haploid hyphae of compatible mating types
-In some, fusion immediately results in
diploid (2n) cell
-Others, have dikaryotic stage (1n + 1n)
Spores are the most common means of
reproduction among fungi
-May form from sexual or asexual processes
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General Biology of the Fungi
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How they acquire foodexternal digestion
Fungi secrete digestive enzymes into their
substrates
-They then absorb the organic molecules
Fungi can break down cellulose and lignin
Some fungi are
carnivorous
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General Biology of the Fungi (Cont.)
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Phylogenetic Relationships
There are five major fungal phyla
-Based on mode of sexual reproduction
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Zygomycetes
Ascomycetes
Ascomycetes (phylum Ascomycota) contain
about 75% of the known fungi
-Include bread yeasts, common molds and
many serious plant pathogens
-Also cup fungi and morels
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Ascomycetes
Yeasts are unicellular ascomycetes
-Most reproduce asexually by budding
Yeasts can ferment
carbohydrates
-Break down glucose
into ethanol and CO2
-Used to make bread, beer and wine
-Saccharomyces cerevisiae
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Basidiomycetes
Basidiomycetes (phylum Basidiomycota)
include some of the most familiar fungi
-Mushrooms, puffballs, jelly fungi
-Plant pathogens such as rusts and smuts
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Basidiomycetes
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Ecology of Fungi
Fungi, together with bacteria are the principal
decomposers in the biosphere
Fungi are virtually the only organisms capable
of breaking down cellulose and lignin
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Ecology of Fungi
Lichens are symbiotic associations between a
fungus and a photosynthetic partner
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Ecology of Fungi
Mycorrhizae are mutualistic relationships
between fungi and plants
-Found on the roots of about 90% of all
known vascular plant species
-Two principal types
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Ecology of Fungi
-Leaf-cutter Attini ants have domesticated
fungi which they keep in underground garden
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