Classification of Fungi
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Transcript of Classification of Fungi
What is a fungus?
A eukaryotic, heterotrophic organism devoid of chlorophyll that obtains its nutrients by absorption, and reproduces by spores. The primary carbohydrate storage product of fungi is glycogen.Most fungi have a thallus composed of hyphae (sing. hypha) that elongate by tip growth
The fungal thallus consists of hyphae; a mass of hyphae is a mycelium.
Structure of fungi
The Characteristics of Fungi
Fungi are NOT plants
Hyphae = tubular units of constructionHeterotrophic by absorptionReproduce by sporesEcologically pivotal roles
HyphaeTubularHard wall of chitinCross walls may form compartments (± cells)MultinucleateGrow at tips
Heterotrophic by AbsorptionFungi get carbon from organic sourcesHyphal tips release enzymesEnzymatic breakdown of substrateProducts diffuse back into hyphae
Product diffuses backinto hypha and is used
Nucleus hangs backand “directs”
Modifications of hyphae
Hyphal growth
Hyphae grow from their tipsMycelium = extensive, feeding web of hyphaeMycelia are the ecologically active bodies of fungi
This wall is rigid Only the tip wall is plastic and stretches
Hyphal growth from spore
mycelium
germinatingspore
Reproduce by spores
Spores are reproductive cellsSexualAsexual
Formed:Directly on hyphaeInside sporangiaFruiting bodies
Amanita fruiting body
Pilobolus sporangia
Penicillium hyphae
Kingdom Fungi
Nutritional Type Chemoheterotroph
Multicellularity All, except yeasts
Cellular ArrangementUnicellular, filamentous, fleshy
Food Acquisition Method
Absorptive
Characteristic Features
Sexual and asexual spores
Embryo Formation None
Fungi are ancient
Major fungal lineages are ancient, perhaps emerging one billion years agoFungi were present before the emergence of animals and vascular plants
KINGDOM
CHARACTERISTIC EXAMPLE
Monera Prokaryocyte BacteriaActinomyces
Protista Eukaryocyte Protozoa
Fungi Eukaryocyte * Fungi
Plants Eukaryocyte PlantsMoss
Animals Eukaryocyte * ArthropodsMammals
Man
Hierarchical Classification
Kingdom Fungi Phylum Basidiomycota Class Basidiomycetes Order Agaricales Family Agaricaceae Genus Agaricus Species: Agaricus campestris L.
Fungus versus Fungi
“Fungus” is used inclusively for a heterogenous group of organisms that have traditionally been studied by mycologists “Fungi” refers to the organisms in the Kingdom Fungi, the true fungi, also called the “Eumycota”
How many species of fungi exist?
- 80,000 species of fungi described
- 1,700 new species described each year
How many species of fungi exist?
- 80,000 species of fungi described
- 1,700 new species described each year
Basic Characteristics and Life Cycles
Ascomycota (inc.Deuteromycetes)BasidiomycotaZygomycotaMitosporic Fungi (Fungi Imperfecti)
Ascomycota – “sac fungi”
Teleomorphic fungiProduce sexual and asexual spores
Sex. – asciAsex. – commonCup fungi, morels, trufflesImportant plant parasites & saprobesYeast - SaccharomycesSeptateMost lichens
A cluster of asci with spores inside
Basidiomycota – “club fungi”
Produce basidiospores and sometimes conidiosporesSex – basidiaAsex – not so commonLong-lived dikaryotic myceliaRusts & smuts – primitive plant parasitesSeptateMushrooms, polypores, puffballsEnzymes decompose woodMycorrhizas
SEM of basidia and spores
Zygomycota – “zygote fungi”
Conjugation fungiCoenocyticSex - zygosporangiaAsex - common
Produce sporangiospores and zygosporesHyphae have no cross wallsGrow rapidlyRhizopus, Mucor (opportunistic, systemic mycoses)Mycorrhizas
Fig 31.6 Rhizopus on strawberries
True FungiTrue FungiChytridiomycota – “chytrids”- Classified in CMR as true fungi (because of their molecular relationships)Simple fungiProduce motile sporesMostly saprobes and parasites in aquatic habitatsCould just as well be Protists
Fig 31.5 Chytridium growing on spores
True Fungi versus Slime MouldsTrue fungi:- those that are hyphal- possess cell walls throughout most of their life cycle - are exclusively absorptive in their nutrition.
Slime moulds:- those that do not form hyphae- lack cell walls during the phase that they obtain nutrients and grow- are capable of ingesting nutrients by phagocytosis.
So they are more common to Protista although they produce fruiting bodies like fungi.
- The most studied of them are the cellular slime moulds and the plasmodial slime moulds or Myxomycetes.