Fungi
Chapter 19
Señora Ettinger
Answer these questions:
• How do fungi differ from other organisms?
• How does the lifestyle of a fungus enable
it to obtain food?
• What factors make each phylum of fungi
distinctive?
• How do fungi affect humans?
Look at page 406 of your textbook
• What do you see in the main picture on
this page?
• Read the caption. What is really shown in
the picture?
• Are “fungus flowers” made of fungus?
• Why would a fungus go to all the trouble of
making a plant imitate a flower?
Page 406 continued
• Do you think this fungus hurts or helps the
rock cress plant?
• Would you guess that fungi could flower
on its own?
Characteristics of Fungi
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Cell structure
Lifestyle
Food acquisition
Habitat
Cell walls
Fungi—plants?
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Cell wall
Mitosis
Chlorophyll
Dikaryon stage
Other characteristics of Fungi
• Heterotrophs
• Digest food outside its body by
secreted enzymes then absorb the
nutrients
• Typically terrestrial
• Key decomposers of plant material
• Most derive their nutrition from plants
• Cell walls made of chitin
Fungal Niches
• Saprobes• Parasites• Symbiotic
Mutuals
Fungi Structures, page 408, draw and label figure 19-2 here:
Hyphae structure, draw Figure 19-3, page 408 here:
Hyphae
• The dominant structure of fungi
• Long, multinucleated, typically
multicelled, one-cell thick fungal
tissue
• Typically hidden from sight since
fungi grow their hyphae into their food
• Serve as vascular channels along
which nutrients are passed
Mycelium
• What is it?
Septa
• What is it?
Septate
coenocytic
“Recess”
Read Armillaria ostoyae
Part 2:
• Reproduction
• Fungal Divisions
Reproduction
• All nuclei are haploid except for zygote
nuclei (except some Chytridiomycota)
• In the sexual reproduction, hyphae of
two different mating strains meet and
fuse but the two types of nuclei may
coexist without fusion for most of the
life of the fungus
• Fungi reproduce by relasin spores
Reproduction
• Monokaryotic compartment has a
single nucleus
• Dikaryotic compartment has two
genetically distinct nuclei
– Heterokaryotic hyphae have two
kinds of genetically different nuclei
– Homokaryotic hyphae have
genetically similar nuclei
Reproductive Structures
• Sporangia:
• Gametangia:
• Conidia
Fungal Divisions
• Plant-like, this groupings are called
divisions instead of phyla
• Presently differentiated from slime
molds and water molds
Chytridiomycota
Fungal Divisions
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Chytridiomycota
Zygomycota
Ascomycota
Basidiomycota
Deuteromycota (Fungi imperfecti) Your
book doesn’t mention this one.
Chytridiomycota
Chytridiomycota
Read
• Modern Genetics Versus Ancient FrogKilling Fungus.
• Write a synopsis in the space provided.
• Be ready to answer questions
Chytridiomycota
Zygomycota
Zygomycota: What does the name
imply?
• What does the name imply?
Zygomycota some characteristics
Zygomycota
• Non-reproductive hyphae lack
septa
• Include the common bread molds
• Produce zygospores
Life Cycle and Sexual
Reproduction
• Sexual reproduction is via fusion of
multinucleate gametangia
• May occur between same or different
mating types
• Massive, haploid zygospore forms
around diploid zygote nuclei
• Meisois occurs during germination
Asexual Reproduction
• Haploid spores are produced within
sporangia
• Sporangium forms at the tip of erect
hypha, with separating septum
• Spores shed above substrate,
dispersed by wind
Chytridiomycota
Ascomycota
Ascomycota
• Beneficial
• Harmful forms
Yeast
Mold
Morels
True Morel
False Morel
Truffles
Truffles
Cup Fungi
Chestnut Blight
Chestnut Blight
Dutch Elm Disease
Ascomycota
• Has a characteristic reproductive
structure called an ascus.
• A diploid zygote forms within
ascus.
• Asci form on ascocarp of densely
interwoven hyphae
Sexual Reproduction
• Ascogonia are female, have trichogyne
• Antheridia are male, fuse with
trichogyne
• Male nuclei travel to ascogonium to pair
with opposite nuclei
• Heterokaryotic hyphae arise from point
of fusion
• An ascus containing two nuclei forms at
the hyphal tip
Sexual Reproduction
• Nuclei within the ascus fuse, forming
diploid zygote which immediately
undergoes meiosis
• Four haploid daughter nuclei are the
result.
• These haploid daughter nuclei
undergo mitosis to form 8 ascospores
• The ascospores are then released, in
most cases by the ascus bursting.
Asexual Reproduction
• Conidia are produced at the ends
of conidiophores. Conidiophores
are the stalk-like vertical growths
on the hyphae. Spores are formed
at the end of the conidiophores and
are separated by septum and are
called conidia.
• The spores are released and then
germinate
Chytridiomycota
Basidiomycota
Basidiomycota
• Includes mushrooms, jelly fungi,
puffballs, rusts and smuts
• Includes edible as well as
poisonous varieties
Mushrooms
Mushrooms
Mushrooms
Jelly Fungus
Jelly Fungus
Puffballs
Rusts
Rusts
Corn Smut
Basidiomycota
• Characteristic reproductive structure
is called a basidium.
• Syngamy occurs within basidium
• Meiosis occurs immediately, forming
four haploid basidiospores
• Four basidiospores are borne on one
basidium
Sexual Reproduction
• Spore germinates forming homokaryotic
hyphae
• Eventually septa form between nuclei of
primary mycelium
• Dikaryotic, heterokaryotic secondary
mycelium forms when hyphae of different
mating types fuse
• Basidiocarps form of completely dikaryotic
hyphae
• Basidia line the gills of typical mushrooms
Deuteromycota
• Commonly called Fungi Imperfecti
because they exhibit only asexual
reproduction
• Mostly ascomycetes, few
zygomycetes and basidiomycetes
• Many are human and plant pathogens
• Others produce important chemicals
such as penicillin
Parasexuality
• Parasexuality occurs when two
different hyphae fuse forming
heterokaryotic hyphae. The two
different nuclei may exchange
portions of chromosomes between
nuclei.
• Provides a certain amount of genetic
recombination.
Fungal Associations
• Lichens
• Mycorrhizae
Lichens
• Mostly ascomycetes with green
algae and/or cyanobacterium
• Specialized hyphae penetrate or
envelop photosynthetic cells
• Fungal chemical signals direct
photosynthetic metabolism
• Could be considered a form of
controlled parasitism
Lichens
• Reproduction of the fungal portion is
via normal fungal sexual reproduction
• Reproduction of the photosynthetic
component is asexual
• The lichen as a whole can fragment
and be transported by wind… to a
new location to form a new individual
Lichens
• Can inhabit cold, dry, generally harsh
environments
• Help break rock surfaces and prepare
habitat for other organisms
• Coloration of lichen protects
photosynthetic partner
• Can survive adverse conditions by
nearly halting metabolism
Mycorrhizae
• Most plant roots associated with
certain fungi
• Fungus aid in transfer of soil
nutrients into roots
• Plant provides organic carbon to
fungus
• Arbuscular mycorrhizae and
ectomycorrhizae
Arbuscular Mycorrhizae
• Hyphae penetrate outer cells of root
• More common mycorrhizae, generally
a zygomycetes
• May increase yield of crops with less
energy input
Ectomycorrhizae
• Hyphae surround, but do not
penetrate roots
• Less common, mostly
basidiomycetes, some ascomycetes
• Characteristic symbiont of shrubs and
trees
Advantages
• Plants more resistant to drought, cold
and harsh conditions
• May provide better protection against
acid precipitation
• Prevent accumulation of toxic metals
• Speed germination of orchid seeds
• Provide better growth in poor soils