Download Taxonomy Fungi A Variety of Roles The Mycelium

Fungi
Taxonomy
• Domain •Eukarya
• Kingdom •Animalia
•Vertebrata
• Phylum
• Class
•Mammalia
• Eukaryotic
• Heterotrophic
– Decomposers
– Parasites
• Single or multi-celled
•Primate
• Order
•Hominidae
• Family
•Homo
• Genus
• Species •sapien
A Variety of Roles
• Pathogens
• Break down organic compounds in their
surroundings
• Carry out extracellular digestion and absorption
• Spoilers of food supplies
– Mycelium grows into food source
• Used to manufacture
– Tips of hyphae secrete digestive enzymes
– Antibiotics
– Cheeses
– Enzymes break down organic material into simple
forms that can be absorbed by hyphae
• Decomposers!
• Plants benefit because some carbon and
nutrients are released
The Mycelium
• Most fungi produce a multicellular feeding
structure called a mycelium
• It consists of branching tubular cells called
hyphae
– High surface-to-volume ratio
– cell walls contain chitin
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Fungal Life Cycle
The Mycelium
• No motile stage
one cell (part
of one hypha of
the mycelium)
• Asexual and sexual spores produced
• Spores germinate after dispersal
• In multi-celled species, spores give rise to
a new mycelium
p.390
Fungal spores
• Withstand extreme conditions of dryness,
heat or cold.
• Disperse by wind or water to distant
locations.
Diversity
• 56,000 known species
– + a million unknown?
• Remain dormant until environmental
conditions favor germination
• Fungal classification is based on type
of sexual spores
Chytrids and microsporidians
• Oldest
– Flagellated spores
• Intracellular parasites
– Chytridiomycosis
• infectious disease that affects
amphibians worldwide
Zygote Fungi (Zygomycetes)
• 1% of known species
• Successful, rapid reproducers
– Produce and disperse hundreds of spores
from hyphae tips
– Bread molds
– Zygomycosis- malnourished, diabetics, burns,
weakened immune systems
– Increased infection of humans suffering from
compromised immune symptoms, e.g.HIV
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Club fungi (Basidiomycota)
• 25,000 species
• Reproductive structures protrude out from
mycelium
– “mushrooms”
– Caps with gills on
surface that have
spores
Examples of club fungi
mushrooms
rusts & smuts pathogens of cereal
crops
Puffballs
Stinkhorns
Shelf fungi
Bird’s nest fungi
Sac Fungi (Ascomycota)
Edible sac fungi:
– Tuber melanosporum (truffles)
– Morchella esculenta (morels)
• Most diverse group
– (30,000 species)
Disease-causing sac fungi:
• Produce sexual ascospores in sac-shaped
cells call asci
• Multicelled species form reproductive
structures called ascocarps that enclose
the asci
– Cup-shaped, flask-shaped or globular
Diversity of Ascomycetes
– Candida albicans - yeast infections
– Ophiostoma ulmi - Dutch elm disease
Useful sac fungi:
– Penicillium chrysogenum - antibiotic
– Saccharomyces cerevisiae - brewing &
baking
Human Pathogens & Toxins
• Ascomycetes cause
– Candida (“yeast”) infections
– Ringworm
– Athlete’s foot
– Ergotism
• Eating some basidiomycetes (Club) can be
fatal
Fig. 24-9b, p.396
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Lichen
Fungal Symbiosis
Lichen
Mycorrhizae
• Combination of fungus
and
photosynthetic organism
• Organisms are symbionts
• Relationship is a
mutualism
Lichen: A Composite Organism
• Fungal mycobiont + photosynthetic
photobiont
• Fungal component usually is ascomycete
• Photobiont is cyanobacteria or green
algae
• Fungus composes bulk of the structure
Lichen Cross Section
dispersal fragment
(cells of fungus and of
photosynthetic species)
outer layer
of fungal cells
photosynthetic
species
inner layer of
loosely woven
hyphae
outer layer of
fungal cells
Fig. 24-11d, p.398
Ecological Roles of Lichens
• Survive in hostile habitats and colonize
new habitats
– Absorb mineral ions from substrates
• Cyanobacteria-containing lichens can fix
nitrogen
Early Warning Systems
• Lichens are very sensitive to deteriorating
environmental conditions
• Absorb toxins but cannot get rid of them
• Can serve as environmental indicators
– Convert atmospheric nitrogen to a form
plants can use
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Mycorrhizae
Mycorrhizae
• “Fungus-root”
• Mutualism between a fungus and a tree
root
• Fungus gets sugars from plant
• Plant gets minerals from fungus
• Many plants do not grow well without
mycorrhizae
Fig. 24-15b, p.399
Mycorrhizae
small, young
tree root
hyphal
strands
Fig. 24-15a, p.399
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