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Biology
Biology
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21-2 Classification of Fungi
Photo Credit: ©D. Cavagnaro/DRK Photo
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Classification
Fungi are classified according to their structure and method of reproduction.
The four main groups of fungi are:
Common molds (Phylum Zygomycota)
Sac fungi (Phylum Ascomycota)
Club fungi (Phylum Basidiomycota)
Imperfect fungi (Phylum Deuteromycota)
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The Common Molds
The Common Molds p530
Familiar molds that grow on meat, cheese, and bread are called zygomycetes.
Terrestrial organisms
Zygomycetes have life cycles that include a zygospore.
A zygospore is a resting spore that contains zygotes formed during the sexual phase of the mold's life cycle.
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The Common Molds
Life Cycle of a Black Bread Mold
p531
MEIOSIS
FERTILIZATION
Zygomycetes have life cycles that include a zygospore. During sexual reproduction in the bread mold Rhizopus stolonifer, hyphae from two different mating types form gametangia. The gametangia fuse, and zygotes form within a zygospore. The zygospore develops a thick wall and can remain dormant for long periods. The zygospore eventually germinates, and a sporangium emerges. The sporangium reproduces asexually by releasing haploid spores produced by meiosis.
Sexual Reproduction
Asexual Reproduction
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The Common Molds
Rootlike hyphae, called rhizoids, penetrate the body of its food source.
Rhizoids
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The Common Molds
The hyphae that run along the surface of the food source are called stolons.
Stolon
Rhizoids
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The Common Molds
The hyphae that push up into the air are the sporangiophores, which form sporangia at their tips.
sporangia
greek: phoros = Holder
sporangiophore: Sporangium holder
sporangiophores
Stolon
Rhizoids
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The Common Molds
Hyphae from different mating types fuse and produce gamete-forming structures called gametangia.
sporangia
Gametangia
+ Mating type (N)
- Mating type (N)
sporangiophores
Stolon
Rhizoids
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The Common Molds
Haploid (N) gametes produced in the gametangia fuse with gametes of the opposite mating type to form diploid (2N) zygotes.
Zygotes develop into thick-walled zygospores.
The zygospore produces spores and the spores are eventually released and grow into new hyphae.
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The Sac Fungi
The Sac Fungi p532
The phylum Ascomycota is named for the ascus, a reproductive structure that contains spores.
The largest phylum – more than 30,000 species
Includes morels, yeast, cup fungus, truffles
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The Sac Fungi
Fruiting bodies – the part of the fungus you see above ground.
It contains the spore producing structures.
The morel and the truffle are edible ascomycetes.
Many wild mushrooms are poisonous and look identical to edible ones. The decision to eat a wild mushroom should only be made by an expert mycologist.
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The Sac Fungi
Yeasts
Yeasts are unicellular fungi.
Reproduction is usually asexual but under the right conditions a yeast cell can reproduce sexually.
Dry granules of yeast contain ascospores, which become active in a moist environment.
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The Sac Fungi
Life Cycle of Sac Fungi p533
The life cycle of an ascomycete usually includes both asexual and sexual reproduction.
Asexual reproduction: spores called conidia are formed at the tip of conidiophores
Sexual reproduction: a tiny sac called ascus contains ascospores
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15. Sexual reproduction of the sac fungi

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The Club Fungi
The Club Fungi p534
The phylum Basidiomycota, or club fungi
Most of what we call mushrooms fit into this phylum.
Also include the bracket fungi which are found growing on the surface of trees.
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The Club Fungi
The Club Fungi p534
The visible part of the fungus is the reproductive part.
The spore producing structure is called the basidium, which is found in the cap of the mushroom.
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The Club Fungi
Life Cycle of Club Fungi
Basidiomycetes undergo an elaborate the most complex life cycle of the fungi.
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The Club Fungi
Life Cycle of Club Fungi p534
The club fungi are named after the club shape of their reproductive structure, the basidium. The cap of a basidiomycete such as a mushroom is composed of tightly packed hyphae. The lower side of the cap is composed of gills—thin blades of tissue lined with basidia that produce basidiospores.
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The Club Fungi
When the right combination of moisture and nutrients occurs, spore-producing fruiting bodies push above the ground.
Fruiting body (N + N)
Gills lined with basidia
Gills
Cap
Stalk
Base
Basidia (N +N)
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The Club Fungi
Diversity of Club Fungi
Basidiomycetes include shelf fungi, puffballs, toadstools, earthstars, jelly fungi, and plant parasites known as rusts.
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The Club Fungi
Diversity of Club Fungi
Mushrooms as Meat-Eaters
Ten species of mushrooms prey upon animals for food.
They attack nematodes (roundworms) in soil and rotting wood.
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The Imperfect Fungi
The Imperfect Fungi p536
Imperfect fungi, or Deuteromycota, are fungi that cannot be placed in other phyla because researchers have never been able to observe a sexual phase in their life cycles.
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The Imperfect Fungi
A well-known genera of the imperfect fungi is Penicillium.
Penicillium notatum is a mold that grow on fruit and is the source of the antibiotic penicillin.
Believed to be related to ascomycetes – similar asexual reproduction
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The Imperfect Fungi
Deuteromycota includes the fungus that cause :
Athlete’s foot
Ringworm
other skin infections
black spot of roses
tomato blight
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21-3 Ecology of Fungi
Photo credits: ©D. Cavagnaro/DRK Photo
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21-3 Ecology of Fungi
The oldest known fungi fossils are about 230 million years old.
Fungi may have helped early plants obtain nutrients and may have been essential to plants’ colonization of the land.
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29. All Fungi Are Heterotrophs
Fungi rely on other organisms for energy.
Many fungi are saprobes, which are organisms that obtain food from decaying organic matter.
Other fungi are parasites, which harm other organisms while living directly on or within them.
Other fungi are symbionts that live in close and mutually beneficial association with other species.
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Fungi as Decomposers
Fungi as Decomposers
What is the main role of fungi in natural ecosystems?
Fungi maintain equilibrium in nearly every ecosystem, where they recycle nutrients by breaking down the bodies and wastes of other organisms.
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21-2
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21-2
Fungi grow best in an environment that is
cool.
moist.
dry.
salty.
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21-2
Yeasts are
ascomycetes.
zygomycetes.
basidiomycetes.
deuteromycetes.
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21-2
Penicillium is a(an)
ascomycete.
basidiomycete.
deuteromycete.
zygomycete.
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21-2
Sac fungi have a characteristic reproductive structure called a(an)
ascus.
basidium.
budding capsule.
sporophyte.
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21-2
The basidiospores of club fungi are produced on thin structures called
fruiting bodies.
buttons.
gills.
stalks.
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