Transcript
MIC 206MYCOLOGY
CLASSIFICATION OF FUNGI
Sub-TopicBrief Criteria of the Fungi KingdomDifferences between the Old and Modern ClassificationDifficulties of Classifying FungiIntroduction, Basic Characteristics and Life Cycles
Definitions
MYCOLOGISTS MYCOLOGY MYCOSESFUNGUSFUNGI
Definitions
Mycologists : scientists who study fungi.Mycology : scientific discipline dealing with fungi. Mycoses : diseases caused in animals by fungi.
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?
- 90,000 species of fungi described
- 1,700 new species described each year
What is a fungus? A eukaryotic organisms. Fungi are neither a plants, nor animals A heterotrophic organism devoid of chlorophyll that obtains its nutrients by absorption.Heterotrophic by absorption.Reproduced 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 – hyphae, mycelium, thalusHeterotrophic by AdsorptionReproduced by Spores
The Characteristics of Fungi
Kingdom Fungi
Nutritional Type Heterotroph
Multicellularity All, except yeasts
Cellular ArrangementUnicellular, filamentous, fleshy
Food Acquisition Method
Absorptive
Characteristic Features
Sexual and asexual spores
Embryo Formation None
Structure of fungi
1) The Structure - HyphaeHyphae = tubular units of constructionTubularHard wall of chitinCross walls may form
compartments (± cells)MultinucleateGrow at tips
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
germinatingspore
mycelium
2. Heterotrophic by Absorption
Fungi 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”
3. Reproduced by spores
Spores are reproductive cellsSexualAsexual
Formed:Directly on hyphaeInside sporangiaFruiting bodies
Amanita fruiting body
Pilobolus sporangia
Penicillium hyphae
OLD AND MODERN
CLASSIFICATION OF FUNGI
Carl Linnaeus (1707-1778) the “Father of Taxonomy”
“ Minerals exist; plants exist and live; animals exist, live and sense.” Plants without obvious sexual organs were classified in Class Cryptogamia (lichens, fungi, mosses, ferns)
Fungi are primitive plants under this classification of organisms.
Old Classification
The Five kingdom system (Whittaker, 1969)Eukarya (includes all organism with a nucleus & membrane bound organelles). Plants and Animals are fairly obviousFungi, are very distinct from the other kingdoms.Kingdom Protista is a “dumping ground” for organisms that don’t fit into the other eukaryotic kingdoms.
Old Classification
R. H. Whittaker’s 1969 Classification
KINGDOM
CHARACTERISTIC EXAMPLE
Monera Prokaryocyte BacteriaActinomyces
Protista Eukaryocyte Protozoa
Fungi Eukaryocyte * Fungi
Plants Eukaryocyte PlantsMoss
Animals Eukaryocyte * ArthropodsMammals
Man
Modern Classification At least 7 kingdoms are now recognized (Patterson & Sogin 1992) : Eubacteria, Archaebacteria, Animalia, Plantae, Eumycota, Stramenopila (Chromista), Protoctista (Protozoa, Protista)
Based on molecular evidence: base sequences from ribosomal RNA (Patterson & Sogin 1992)
Systems of classifying fungi 1) 1860
HOGG proposed the term PROTOCTISTA - fungi and neither Plant or Animal. This kingdom composed mostly of unicellular organisms. The kingdom was later replaced by 2 kingdoms – MYCOTA & MONERA (prokaryotes) and PROTOCTISTA(eukaryotes).
2) 1947Microscopes enable study of complex structural
characteristics.New classification (WOLF & WOLF, 1947)
3) 1969Fungi in its own kingdom by WHITTAKER – FUNGI KINGDOM.
Systems of classifying fungi
4) 1998Modification by MARGUILIS & SCHWARTZ – used characteristics (structure & function).
• MONERA: Prokaryotes – bacteria, actinomycetes, blue-green algae.
• PROTOCTISTA: Eukaryotes – protozoa and other unicellular and colonial organisms such as water moulds, slime moulds and slime nets.
• FUNGI : Eukaryotes – organisms that lack flagella that develop from spores such as yeast, molds, rusts and mushrooms.
• PLANTAE: Eukaryotes – organisms that develop from embryos such as liverworts, mosses and vascular plants.
• ANIMALIA: Eukaryotes – organisms that develop from a blastula (hollow ball of cells) such a sponges, worms, arthropods and mammals.
Marguilis and Schwartz (1998)
Classify the fungi into 3 phyla : Zygomycota, Ascomycota and Basidiomycota.
Chytrids (CHYTRIDIOMYCOTA) in the Kingdom Proctista.
Deuteromycota with their closest relatives that are the Ascomycota and Basidiomycota.
Lichen with the Phylum Ascomycota.
Other classifications MOORE, 1998 (quoted from Pfieffer, M., et al.,
2001) states that plants, animals and fungi can be separated based on how they obtain energy.
Plants possess chloroplasts as photosynthetic structures used to produce food.
Animals possess mitochondria used for internalized digestion.
Fungi excrete enzymes into the food source they live within external digestion.
Classification using molecular research techniques
BALDAUF & PALMER (1993), WAINWRIGHT et al. (1993) and HASEGAWA et al (1993)
The above current schemes agree that the three major kingdoms are separated
→ thereby confirmed that there are no connection between the fungi-plant kingdom.
Question
Fill in the blanks of the systematic of classification
1) Kingdom2) Division / Phylum3) ___________ 4) Order5) ___________ 6) Tribe7) ___________ 8) Species
Sometimes there are subdivisions and subclasses
Question
Fill in the blanks of the systematic of classification
1) Kingdom2) Division / Phylum3) Class 4) Order5) Family 6) Tribe7) Genus 8) Species
Sometimes there are subdivisions and subclasses
Hierarchical Classification
Kingdom Fungi Phylum Basidiomycota Class Basidiomycetes Order Agaricales Family Agaricaceae Genus Agaricus Species: Agaricus campestris L.
How are fungi named?
To determine the correct name for a taxon, certain steps must be followed, including: Effective publication Valid publication
• Description or diagnosis in Latin• Clear indication of rank• Designated type
NomenclatureNomenclature: the “allocation of scientific names to the units a systematist considers to merit formal recognition.” (Hawksworth et al., 1995. The Dictionary of the Fungi).
The nomenclature of fungi is governed by the International Code for Botanical Nomenclature, as adopted by the International Botanical Congress.
Reasons why it is not easy to classify fungi
Fungi comprise of a broad number of organisms.Fungi have various forms depending on the environment and conditions in which they grow.Many terms being used to describe the morphological structures of fungi.
Basic Characteristics and Life Cycles
Ascomycota (inc.Deuteromycota)BasidiomycotaZygomycota
Ascomycota – “sac fungi”
Teleomorphic fungi Produce sexual and
asexual sporesSex. – 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 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.
QUESTION
The fungus can never be classified in
Plantae or Animalia?
EXPLAIN WHY?
(Hint ! LOOK AT ITS MOBILITY, REPRODUCTION & NUTRITION)
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