The Living World Fourth Edition GEORGE B. JOHNSON Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display PowerPoint ® Lectures prepared by Johnny El-Rady 17 Fungi Invade the Land

Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 17.1 Complex Multicellularity Complex multicellular organisms Individuals are composed of many highly specialized cells that coordinate their activities Three kingdoms exhibit multicellularity Plants Animals Fungi

Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 17.1 Complex Multicellularity Two key characteristics distinguish between complex multicellular and simple multicellular organisms Cell specialization Different cells use different genes They therefore develop in different ways Intercell coordination Cells adjust their activity in response to what other cells are doing

Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 17.2 A Fungus Is Not a Plant The study of fungi is called mycology Fungi have traditionally been included in the plant kingdom However, there are significant differences between fungi and plants Fungi are heterotrophs Fungi have filamentous bodies Fungi have nonmotile sperm Fungi have cell walls made up of chitin Fungi have nuclear mitosis

Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display Fungi exist mainly as slender filaments called hyphae (singular, hypha) Hyphae are strings of cells separated by septa (singular, septum) The Body of a Fungus Pores in the septa allow for cytoplasmic streaming between cells Fig. 17.2a

Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display The main body of a fungus is a mass of hyphae termed a mycelium (plural, mycelia) The Body of a Fungus Fig. 17.2b Because of cytoplasmic streaming, many nuclei may be connected by shared cytoplasm All parts of the fungal body are metabolically active

Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 17.3 Reproduction and Nutrition of Fungi Fungi reproduce both sexually and asexually Sexual reproduction is initiated when two hyphae of different mating types come in contact and fuse The two nuclei do not fuse immediately Heterokaryon Hyphae containing nuclei derived from two genetically different individuals Homokaryon Hyphae containing nuclei derived from two genetically similar individuals

Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 17.3 Reproduction and Nutrition of Fungi Fungi have three types of reproductive structures Gametangia Form haploid gametes that fuse to form zygote Sporangia Produce haploid spores that are dispersed Conidiophores Produce asexual spores Spores are a common means of fungal reproduction Fig Puffball spores

Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 17.3 Reproduction and Nutrition of Fungi Fungi obtain nutrients by external digestion They secrete digestive enzymes into their surroundings and absorb the resulting organic molecules Some fungi are active predators Fig The oyster mushroom Immobilizes nematodes then eats them! Others are even more active predators Snare or trap prey

Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 17.4 Kinds of Fungi There are divided into four phyla Distinguished primarily by their mode of sexual reproduction Zygomycota Ascomycota Basidiomycota Chitrydiomycota A fifth group, the imperfect fungi, is artificial It’s a “catch-all” grouping of fungi in which sexual reproduction has not been observed yet! 73,000 species of fungi have been named so far

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17.5 Zygomycetes Zygomycetes are unique fungi Zygomycetes make up < 1% of named fungi Zygomycetes typically undergo asexual reproduction Their hyphae lack septa Fusion of their hyphae produces a zygote (one 2n nucleus) The other fungi produce a heterokaryon (two n nuclei) They include Bread molds Some pathogens Candida

Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display Fig Life cycle of a zygomycete Rhizopus Effective survival mechanism

Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 17.6 Ascomycetes Phylum Ascomycota, the ascomycetes, is the largest of the four phyla Yeasts, morels and truffles Many plant fungal pathogens Dutch elm disease and chestnut blight Reproduction is usually asexual Spores, or conidia, are cut off by septa at ends of hyphae Ascomycetes are named after a characteristic sexual reproductive structure, the ascus (plural asci) The ascus differentiates within the ascocarp

Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display Fig Life cycle of an ascomycete Morel

Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 17.7 Basidiomycetes Phylum Basidiomycota contains the most familiar of the fungi Mushrooms, toadstools, puffballs Many plant fungal pathogens Rusts and smuts Asexual reproduction is rare Basidiomycetes are named after a club-shaped sexual reproductive structure, the basidium There, haploid nuclei fuse, forming a diploid zygote Zygote undergoes meiosis releasing haploid basidiospores

Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display Fig Life cycle of a basidiomycete Amanita

Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 17.8 Chytridiomycetes, Imperfect Fungi, and Yeasts Chytridiomycetes Aquatic, flagellated fungi Most closely related to ancestral fungi Include Plant pathogens A frog pathogen Fig The pathogenic chytrid, Batrachochytrium dendrobatidis

Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 17.8 Chytridiomycetes, Imperfect Fungi, and Yeasts Imperfect fungi Fungi where sexual reproduction has not been observed Most appear to be ascomycetes Include Fungi that cause ringworm infections Fig The imperfect fungus, Verticillium alboatrum A pathogen of alfalfa

Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 17.8 Chytridiomycetes, Imperfect Fungi, and Yeasts Yeasts Generic name given to unicellular fungi ~ 250 named species Most appear to be ascomycetes Reproduction is mostly asexual Takes place by budding Fig Budding in the yeast Saccharomyces cerevisiae Baker’s yeast

Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display Fig Armillaria: World’s largest organism? 17.9 Ecological Roles of Fungi Fungi, together with bacteria, are the principal decomposers in the biosphere Fungi are virtually the only organisms that can break down lignin Fungi cause animal diseases Fungi are the most harmful pests of living plants Coniferous forest 8 hectares

Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 17.9 Ecological Roles of Fungi Many commercial products are dependent on the biochemical activities of fungi Bread Beer Cheese Soy sauce Penicillin

Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display Mutualism is a form of symbiosis in which each partner benefits Two kinds of mutualistic associations between fungi and autotrophic organisms are ecologically important 1. Mycorrhizae 2. Lichens Fungal Associations

Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display Mycorrhizae Fig Mycorrhizae on the roots of pines Fig How mutualism aids plant growth Symbiotic association between a fungus and the roots of plants Fungus helps plant absorb minerals and nutrients Plant provides fungus with food (organic molecules) No mycorrhizae

Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display Mycorrhizae Endomycorrhizae vs. Ectomycorrhizae Fig Hyphae penetrate root cells Far more common type Hyphae do not penetrate root cells

Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display Lichens Symbiotic association between a fungus and a green algae or cyanobacterium Lichens are found in the harshest of habitats Indeed, they are often the first colonists in such harsh areas Lichens are pollution indicators Fig Lichens growing on rock