Mader 9/e, Biology

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Outline

• Characteristics
• Structure
• Reproduction
• Evolution
• Sac Fungi
• Yeasts
• Club Fungi
• Smuts and Rusts
• Imperfect Fungi
• Symbiotic Relationships

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Characteristics of the Fungi

• Kingdom Fungi contains 80,000 spp
• Mostly multicellular eukaryotes that share a
  common mode of nutrition
• Heterotrophic
• Cells release digestive enzymes and then absorb
  resultant nutrient molecules
• Some are parasitic
• Several have mutualistic relationship

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Structure of Fungi

• Body (thallus) of most fungi is multicellular
  mycelium (yeasts are unicellular)
• Consists of a vast network of thread-like hyphae
• Septate fungi have hyphae with cross walls
• Nonseptate fungi are multinucleated
• Hyphae grow from tip
• Give the mycelium a large surface area per unit
  volume
• Cell walls of chitin, like insect exoskeleton
• Excess food stored as glycogen as in animals
• Possibly evolved from red algae - both lack
  flagella

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Mycelia and Hyphae of Fungi
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Reproduction of Fungi

• Both sexual (in most) and asexual reproduction
• Sexual reproduction involves three stages
• Haploid Hyphae
• Dikaryotic Stage
• Diploid Zygote

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Reproduction of Fungi

• During sexual reproduction, hyphae from two
  different mating types fuse
• Hyphae that contain paired haploid nuclei are
  said to be dikaryotic
• Nuclear fusion produces diploid nucleus, which
  produces haploid windblown spores by meiosis
• Spores germinate directly into haploid hyphae
  without embryological development
• Asexual reproduction usually involves the
  production of windblown spores
• Unicellular yeasts reproduce by budding

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Dispersal of Spores
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Diversity of FungiZygomycota

• Zygospore Fungi
• Phylum Zygomycota
• Mainly saprotrophs decomposing animal and plant
  remains
• Black bread mold - Rhizopus stolonifer

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Black Bread Mold,Rhizopus stolonifer
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Diversity of FungiZygomycota

• Life cycle
• Hyphae of opposite mating types grow toward each
  other
• Hyphae swell at tips cross walls develop behind
  each end form gametangia
• Gametangia merge resulting in a large
  multi-nucleate cell
• Nuclei of the two mating types pair and then fuse
• A thick wall develops around the zygospore
• The zygospore becomes dormant for period
• Sporangiophore(s) then sporangia develop, spores
  released
• Spores dispersed by air currents germinate into
  mycelia

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Diversity of FungiSac Fungi

• Phylum Ascomycota - about 60,000 species of sac
  fungi
• Most are saprotrophs that digest resistant
  materials containing cellulose, lignin, or
  collagen
• Most are composed of septate hyphae
• Neurospora, experimental organism for the
  one-gene-one-enzyme studies
• Morels and truffles, famous gourmet delicacies
  revered throughout the world
• Many plant diseases Powdery mildews leaf curl
  fungi ergot of rye chestnut blight and Dutch
  elm disease
• Aspergillus and Candida cause serious human
  infections
• Talaromyces (formerly Penicillium) is source of
  penicillin

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Sac FungiReproduction - Asexual

• Life cycle
• Asexual reproduction is the norm
• Yeasts usually reproduce by budding
• A small bulge forms on side of cell
• Receives a nucleus and gets pinched off and
  becomes full size
• The other ascomycetes produce spores called
  conidia or conidiospores
• Vary in size and shape and may be multicellular
• Conidia usually develop at the tips of
  conidiophores
• Conidiophores differ in appearance and are
  diagnostic
• Conidia are windblown
• Conidia of Cladosporium cause allergies -
  concentrations of more than 35,000 conidia/m3
  over Leiden (Germany)

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Asexual Reproduction in Sac Fungi
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Sac FungiReproduction - Sexual

• Life cycle, cont.
• Sexual reproduction
• Ascus refers to the fingerlike sac that develops
  during sexual reproduction
• Asci usually surrounded and protected by sterile
  hyphae within an ascocarp
• In cup fungi, ascocarps are cup-shaped
• In morels they are stalked and are pitted like
  the surface of the moon
• Haploid hyphae fuse to make diploid nucleus
• Mitosis and then meiosis produces 8 ascospores

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Sexual Reproduction in Sac Fungi
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Black Mold
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Tineas
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Sac FungiReproduction - Yeasts

• Term yeasts is loosely applied to unicellular
  fungi, many of which are ascomycetes
• Budding is common form of asexual reproduction
• Sexual reproduction results in the formation of
  asci and ascospores
• When some yeasts ferment, they produce ethanol
  and carbon dioxide

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Diversity of FungiThe Club Fungi

• Phylum Basidomycota 22,000 spp
• Familiar toadstools, mushrooms, bracket fungi,
  puffballs, stinkhorns some deadly poisonous
• Also plant diseases such as the smuts and rusts
• Mycelium composed of septate hyphae

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The Club FungiReproduction

• Usually reproduce sexually
• Haploid hyphae fuse, forming a dikaryotic (n n)
  mycelium
• Dikaryotic mycelium forms fruiting bodies called
  basidiocarps
• Contain club-shaped structures called basidia
• Nuclear fusion followed by meiosis produces
  basidiospores (up to 40,000,000 per hour)

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Club Fungi
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Club Fungi
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The Club FungiSmuts and Rusts

• Smuts and rusts are club fungi that parasitize
  cereal crops
• Great economic importance because of annual crop
  losses
• Do not form basidiocarps
• Life cycle of rusts often requires two different
  plant host species
• Black stem rust of wheat uses barberry bushes
• Blister rust of white pine uses currant and
  gooseberry bushes
• Eliminating these bushes in crop areas keeps
  rusts in check
• Wheat rust
• Controlled by breeding new resistant strains of
  wheat
• Requires continuous development, because rust can
  mutate

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Smuts Rusts
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Symbiotic RelationshipsLichens

• Symbiotic association between a fungus and a
  cyanobacterium or green alga
• Specialized fungal hyphae penetrate
  photosynthetic symbiont
• Transfer nutrients directly to the fungus
• Possibly mutualistic, but fungal symbiont
  probably a parasite of photosynthetic symbiont
• Photosynthetic symbiont independent
• Fungal symbiont usually cant grow alone

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Symbiotic RelationshipsLichens

• Three morphological types
• Compact crustose lichens - seen on bare rocks or
  on tree bark
• Fruticose lichens shrub-like
• Foliose lichens - leaf-like
• Can live in areas of extreme conditions and
  contribute to soil formation
• Sensitive indicators of air pollution

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Lichen Morphology
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Symbiotic RelationshipsMycorrhizae

• Mutualistic relationships between soil fungi and
  the roots of most familiar plants
• Give plant greater absorptive surface
• Help plants acquire mineral nutrients in poor
  soil
• Fungal symbiont usually a sac fungus
• Hyphae may enter cortex of root, but not
  cytoplasm
• Ectomycorrhizae form a mantle that is exterior to
  the root, and they grow between cell walls.
• Endomycorrhizae penetrate only the cell walls
• Earliest fossil plants have mycorrhizae
  associated with them

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Plant Growth Experiment
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Review

• Characteristics
• Structure
• Reproduction
• Evolution
• Sac Fungi
• Yeasts
• Club Fungi
• Smuts and Rusts
• Imperfect Fungi
• Symbiotic Relationships

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