Biology, Seventh Edition
Solomon • Berg • Martin
Chapter 25
Kingdom Fungi
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Biology, Seventh Edition
CHAPTER 25 Kingdom Fungi
• Kingdom Fungi contains more
than 81,000 known species
(most terrestrial)
• All fungi are eukaryotes
• Cells contain
–Membrane-enclosed nuclei
–Mitochondria
–Other membranous organelles
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Biology, Seventh Edition
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CHAPTER 25 Kingdom Fungi
Fungi are heterotrophs
Most are decomposers
Some are parasites
Found universally wherever
organic material is available
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Biology, Seventh Edition
CHAPTER 25 Kingdom Fungi
• Optimum pH for most species is
ca. 5.6
• Some can tolerate pH ranges
from 2 to 9
• Many can grow in
• Concentrated salt solutions
• Sugar solutions, e.g. jelly
• Fungi tolerate wide temperature
range
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Biology, Seventh Edition
CHAPTER 25 Kingdom Fungi
• Characteristics of fungi
• Enclosed by cell walls at some
stage in life cycle
–Most fungi have cell walls
consisting of complex
carbohydrates including chitin
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Biology, Seventh Edition
CHAPTER 25 Kingdom Fungi
• Two main types: molds and
yeasts
• Vegetative body plan of molds
consists of hyphae
• Hyphae form mycelium
–Some hyphae are coenocytic
–Some are divided by septa into individual
cells containing one or more nuclei
• Yeasts are unicellular
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Biology, Seventh Edition
CHAPTER 25 Kingdom Fungi
Fungus body plan
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Biology, Seventh Edition
CHAPTER 25 Kingdom Fungi
• Most fungi reproduce by
spores, either nonmotile or
motile
• Spores usually produced on
• Specialized aerial hyphae
–Aerial hyphae of some fungi form
fruiting bodies
• Fruiting structures
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Biology, Seventh Edition
CHAPTER 25 Kingdom Fungi
Germination of a spore to form a mycelium
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Biology, Seventh Edition
CHAPTER 25 Kingdom Fungi
• Germination of a fungal spore
• Hypha emerges
• Mycelium infiltrates growth
medium
• Mycelium degrades complex
organic compounds to small
organic molecules
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Biology, Seventh Edition
CHAPTER 25 Kingdom Fungi
• Four main phyla
• Chytridiomycota
• Zygomycota
• Ascomycota
• Basidiomycota
• Fungi that do not fit these phyla
classified as Deuteromycota
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Biology, Seventh Edition
CHAPTER 25 Kingdom Fungi
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Biology, Seventh Edition
CHAPTER 25 Kingdom Fungi
• Chytridiomycetes are the most
primitive fungi alive today
• Produce flagellate cells at some
stage in their life cycle
• No other fungal phyla are
flagellate
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Biology, Seventh Edition
CHAPTER 25 Kingdom Fungi
Fungal evolution
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Biology, Seventh Edition
CHAPTER 25 Kingdom Fungi
• Distinguishing characteristics of
chytridiomycetes
• Motile cells have a single,
posterior flagellum
• Reproduce sexually and
asexually
• Are parasites or decomposers
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Biology, Seventh Edition
CHAPTER 25 Kingdom Fungi
• Life cycle of Allomyces
• Has an alternation of generations:
spends part of its life as a haploid
thallus and part as a diploid
–Haploid thallus bears male and
female gametangia
–When a flagellate male gamete fuses
with a flagellate female gamete,
result is a diploid thallus
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Biology, Seventh Edition
CHAPTER 25 Kingdom Fungi
Life cycle of
Allomyces
arbuscula
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Biology, Seventh Edition
CHAPTER 25 Kingdom Fungi
• Distinguishing characteristics of
zygomycetes
• All produce zygospores
• Hyphae are coenocytic
• Septa form to separate the
hyphae from reproductive
structures
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Biology, Seventh Edition
CHAPTER 25 Kingdom Fungi
• Life cycle of Rhizopus stolonifer
• Hyphae meet to form gametangia
• Gametangia unite, the nuclei fuse
• A single zygospore develops
• Meiosis occurs, zygospore
germinates
• Emerging hypha develops a
sporangium
• Spores are released
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Biology, Seventh Edition
CHAPTER 25 Kingdom Fungi
Life cycle of
Rhizopus
stolonifer
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Biology, Seventh Edition
CHAPTER 25 Kingdom Fungi
• Distinguishing characteristics of
ascomycetes
• Sexual spores are produced in
asci
• Hyphae usually have septa, but
cytoplasm is continuous
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Biology, Seventh Edition
CHAPTER 25 Kingdom Fungi
• Life cycle of a typical ascomycete
• Gametangia fuse, forming
dikaryotic hyphae
• Asci develop from dikaryotic
hyphae
• Asci are incorporated into an
ascocarp
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Biology, Seventh Edition
CHAPTER 25 Kingdom Fungi
• Life cycle of a typical ascomycete,
cont.
• In each ascus, the nuclei fuse to
form the zygote
• Meiosis occurs, forming four
haploid nuclei
• Mitosis occurs, producing eight
haploid nuclei
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Biology, Seventh Edition
CHAPTER 25 Kingdom Fungi
• Life cycle of a typical ascomycete,
cont.
• Each haptoid nuclei becomes
incorporated into an ascospore
• When ascospores are released, they
germinate and form new mycelia
• Asexual reproduction involves the
formation of haploid conidia
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Biology, Seventh Edition
CHAPTER 25 Kingdom Fungi
Life cycle of
a typical
ascomycete
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Biology, Seventh Edition
CHAPTER 25 Kingdom Fungi
• Distinguishing characteristics of
basidiomycetes
• Develop basidia
• Each basidium is an enlarged
hyphal cell
• Four basidiospores develop on
the tip of the basidium
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Biology, Seventh Edition
CHAPTER 25 Kingdom Fungi
Basidia line the gills of Omphalotus olearius
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Biology, Seventh Edition
CHAPTER 25 Kingdom Fungi
SEM of a basidium
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Biology, Seventh Edition
CHAPTER 25 Kingdom Fungi
• Life cycle of basidiomycetes
• When a hypha of a primary
mycelium encounters another
monokaryotic hypha of a different
mating type, the two hyphae fuse
• The two haploid nuclei remain
separate
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Biology, Seventh Edition
CHAPTER 25 Kingdom Fungi
• Life cycle of basidiomycetes, cont.
• A secondary mycelium is produced
• The n +n hyphae of the secondary
mycelium grow
• The hyphae form buttons along the
mycelium
• Button develops into a basidiocarp
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Biology, Seventh Edition
CHAPTER 25 Kingdom Fungi
• Life cycle of basidiomycetes, cont.
• In the young basidia, haploid nuclei
fuse, forming diploid zygotes
• Meiosis takes place, forming four
haploid nuclei
• Extensions of the basidium develop
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Biology, Seventh Edition
CHAPTER 25 Kingdom Fungi
• Life cycle of basidiomycetes, cont.
• The nuclei and some cytoplasm
move into the basidium
• Each extension of the basidum
becomes a basidiospore
• A septum forms, separating
basidiospore from the rest of the
basidium
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Biology, Seventh Edition
CHAPTER 25 Kingdom Fungi
Life cycle of a typical
basidiomycete
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Biology, Seventh Edition
CHAPTER 25 Kingdom Fungi
• Distinguishing characteristics of
deuteromycetes
• Are all similar, but are probably
polyphyletic
• Do not have a common ancestor
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Biology, Seventh Edition
CHAPTER 25 Kingdom Fungi
• Most deuteromycetes have no
sexual stage during their life cycle
• Some have lost the ability to
reproduce sexually
• Others reproduce sexually only
rarely
• Most reproduce only by means of
conicidia
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Biology, Seventh Edition
CHAPTER 25 Kingdom Fungi
• Lichen
• Dual organism: symbiotic
association between a phototroph
and a fungus
–Phototrophic component is either a
green alga, a cyanobacterium, or
both
–Fungus is an ascomycete or a
basidiomycete
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Biology, Seventh Edition
CHAPTER 25 Kingdom Fungi
Cross section of a
typical lichen
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Biology, Seventh Edition
CHAPTER 25 Kingdom Fungi
• Typically, lichens exhibit one of
three different growth forms
• Crustose
• Foliose
• Fruticose
• Lichens reproduce mainly
asexually
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Biology, Seventh Edition
CHAPTER 25 Kingdom Fungi
Crustose,
foliose, and
fruticose
growth forms
Crustose Lichens
(Bacidia, Lecanora)
Foliose lichen (Parmelia)
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Biology, Seventh Edition
CHAPTER 25 Kingdom Fungi
• Ecological significance of fungi
as decomposers
• Absorb nutrients from organic
wastes
• Release water, CO2, and mineral
components of organic
compounds
• These elements are recycled
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Biology, Seventh Edition
CHAPTER 25 Kingdom Fungi
• The ecological role of
mycorrhizae
• Mycorrhizal fungus decomposes
organic material in soil
• Benefit plants by increasing their
absorptive surface area
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Biology, Seventh Edition
CHAPTER 25 Kingdom Fungi
• The ecological role of
mycorrhizae, cont.
• Roots supply fungus with sugars,
amino acids, and other organic
substances
• Scientists have measured
movement of organic materials from
one tree species to another
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Biology, Seventh Edition
CHAPTER 25 Kingdom Fungi
Western red cedar grown without mycorrhizae
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Biology, Seventh Edition
CHAPTER 25 Kingdom Fungi
Western red cedar grown with mycorrhizae
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Biology, Seventh Edition
CHAPTER 25 Kingdom Fungi
• Economic and medical
importance of fungi
• Beverages
• Food
• Medicine
• Chemicals
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Biology, Seventh Edition
CHAPTER 25 Kingdom Fungi
• Fungal diseases of plants
• Dutch elm disease
• Chestnut blight fungus
• Smuts and rusts
• Verticillium wilt
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Biology, Seventh Edition
CHAPTER 25 Kingdom Fungi
• Fungal diseases of humans
• Ringworm and athlete’s foot
• Histoplasmosis
• Aspergillosis
• Cancer (contributory factor)
• Sick building syndrome (contributory factor)
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