Chapter 22 The Diversity of Fungi Lecture Outlines by Gregory Ahearn University of North Florida Copyright 2011 Pearson Education Inc Chapter 22 At a Glance 22 1 What Are the Key Features of Fungi 22 2 What Are the Major Groups of Fungi 22 4 How Do Fungi Affect Humans Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 22 1 What Are the Key Features of Fungi Fungal bodies consist of slender threads Most fungi are multicellular Cells are surrounded by cell walls composed of chitin a nitrogen containing polysaccharide The body of almost all fungi is a mycelium an interwoven mass of threadlike filaments called hyphae singular hypha Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 22 1 What Are the Key Features of Fungi Fungal bodies consist of slender threads continued Hyphae of most species are divided into many cells by partitions called septa singular septum each cell possesses one or more nuclei Pores in the septa allow cytoplasm to stream from one cell to the next Fungi cannot move but grow rapidly in any direction within a suitable environment Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 22 1 What Are the Key Features of Fungi Fungi obtain their nutrients from other organisms Fungi secrete enzymes outside their bodies and absorb the digested nutrients Fungal decomposers feed on dead organic material and wastes Fungal parasites absorb nutrients from cells of living hosts and may cause disease Some symbiotic fungi live in mutually beneficial relationships with other organisms Fungal predators consume living organisms Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 22 1 What Are the Key Features of Fungi Fungi propagate by spores Spores are tiny reproductive packages capable of developing into adult fungi They are often produced in large numbers and are dispersed by animals or air currents Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 22 1 What Are the Key Features of Fungi Most fungi can reproduce both asexually and sexually During asexual reproduction For the most part asexual reproduction occurs under stable conditions A haploid mycelium produces haploid asexual spores by mitosis Spores germinate and develop into a new mycelium by mitosis This results in the rapid production of genetically identical clones Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 22 1 What Are the Key Features of Fungi During sexual reproduction Neighboring haploid mycelia of different but compatible mating types come into contact with each other The two different hyphae fuse so that the nuclei share a The different haploid nuclei fuse to form a diploid zygote The zygote undergoes meiosis to form haploid sexual The spores germinate and develop into a new mycelium common cell spores by mitosis This results in the production of fungal bodies that are genetically distinct from either parent Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 22 2 What Are the Major Groups of Fungi Fungus species are classified into five phyla Chytridiomycota chytrids Zygomycota zygomycetes Glomeromycota glomeromycetes Basidiomycota basidiomycetes Ascomycota ascomycetes Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 22 2 What Are the Major Groups of Fungi The chytrids Most chytrids are aquatic They are distinguished from other fungi by forming flagellated spores that require water for dispersal They reproduce both asexually and sexually Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 22 2 What Are the Major Groups of Fungi The chytrids continued Most feed on dead aquatic material Some species are parasites of plants and animals One chytrid species is a frog pathogen believed to be a major cause of the current worldwide die off of frogs Primitive chytrids are believed to have given rise to the other groups of modern fungi Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 22 2 What Are the Major Groups of Fungi The zygomycetes Most zygomycetes live in soil or on decaying plant or animal material The group includes the black bread mold Rhizopus They reproduce both asexually and sexually Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 22 2 What Are the Major Groups of Fungi The zygomycetes continued During asexual reproduction Haploid spores are produced in black spore cases called sporangia The spores disperse through the air and germinate to form new haploid hyphae Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 22 2 What Are the Major Groups of Fungi The zygomycetes continued During sexual reproduction Two hyphae of different mating types come into contact and fuse to form a zygosporangium that contains multiple haploid nuclei Haploid nuclei fuse within the zygosporangium to form diploid nuclei Diploid nuclei give rise to stalked sporangia that produce haploid spores that disperse germinate and develop into new haploid hyphae Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 22 2 What Are the Major Groups of Fungi The glomeromycetes Glomeromycetes live in intimate contact with the roots of plants Their hyphae penetrate root cells and form microscopic branching structures inside the cell The interaction forms a beneficial relationship called a mycorrhiza Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 22 2 What Are the Major Groups of Fungi The glomeromycetes continued Reproduction in the glomeromycetes Sexual reproduction has not been observed During asexual reproduction clusters of spores are produced by mitosis and remain outside the host plant cell at the tips of hyphae When the spores germinate hyphae grow into the surrounding soil and penetrate new plant roots Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 22 2 What Are the Major Groups of Fungi The basidiomycetes The basidiomycetes are called the club fungi because they produce club shaped reproductive structures These fungi typically reproduce sexually During reproduction two hyphae of different mating types come into contact and fuse resulting in the formation of a fruiting body Each fruiting body contains numerous club shaped structures called basidia singular basidium Nuclei within each basidium fuse forming a diploid nucleus Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 22 2 What Are the Major Groups of Fungi The basidiomycetes continued The diploid nucleus divides by meiosis producing four haploid basidiospores Basidiomycete fruiting bodies are
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