Fungi Chapter 31

2 Defining Fungi Mycologists believe there may be as many as 1.5 million fungal species Fungi are classified into six main groups -Chytrids -Zygomycetes -Glomeromycetes -Ascomycetes -Basidiomycetes -Deuteromycetes

3 Defining Fungi Fungi share the following characteristics 1. Are heterotrophs that absorb nutrients 2. Have a number of different cell types 3. Have cell walls that include chitin 4. Some have a dikaryon stage 5. Undergo nuclear mitosis

4 General Structure of the Fungi Multicellular fungi consist of long, slender filaments called hyphae

5 General Structure of the Fungi A mass of connected hyphae is called a mycelium

6 General Structure of the Fungi Cells walls of fungi are formed of polysaccharides including chitin -Cross-linked with proteins

7 Haploid? Diploid? Hyphae may have more than one nucleus -Monokaryotic – One nucleus -Dikaryotic – Two nuclei

8 Mitosis Fungi have an unusual mitosis -Nucleus does not break down and reform -Instead, they form the spindle apparatus within the nucleus

9 Reproduction Fungi can reproduce sexually and asexually Sexual reproduction involves the fusion of two haploid hyphae of compatible mating types -In some, fusion immediately results in diploid (2n) cell -Others, have dikaryotic stage (1n + 1n) Spores are the most common means of reproduction among fungi -May form from sexual or asexual processes

10 General Biology of the Fungi

11 How they acquire food- external digestion Fungi secrete digestive enzymes into their substrates -They then absorb the organic molecules Fungi can break down cellulose and lignin Some fungi are carnivorous

12 General Biology of the Fungi (Cont.)

13 Phylogenetic Relationships There are five major fungal phyla -Based on mode of sexual reproduction

Zygomycetes

15 Ascomycetes Ascomycetes (phylum Ascomycota) contain about 75% of the known fungi -Include bread yeasts, common molds and many serious plant pathogens -Also cup fungi and morels

16 Ascomycetes Yeasts are unicellular ascomycetes -Most reproduce asexually by budding Yeasts can ferment carbohydrates -Break down glucose into ethanol and CO 2 -Used to make bread, beer and wine -Saccharomyces cerevisiae

17 Basidiomycetes Basidiomycetes (phylum Basidiomycota) include some of the most familiar fungi -Mushrooms, puffballs, jelly fungi -Plant pathogens such as rusts and smuts

18 Basidiomycetes

19 Ecology of Fungi Fungi, together with bacteria are the principal decomposers in the biosphere Fungi are virtually the only organisms capable of breaking down cellulose and lignin

20 Ecology of Fungi Lichens are symbiotic associations between a fungus and a photosynthetic partner

21 Ecology of Fungi Mycorrhizae are mutualistic relationships between fungi and plants -Found on the roots of about 90% of all known vascular plant species -Two principal types

22 Ecology of Fungi -Leaf-cutter Attini ants have domesticated fungi which they keep in underground garden