test3 - Chapter 31 Fungi 1 How many described species of...

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Chapter 31: Fungi 1. How many described species of fungi are there? a. 100,000 – 30% are parasites, mostly on or in plants 2. What are the major nutritional roles of fungi? Examples of each? a. Fungi are heterotrophs b. Secrete exoenzymes to break down complex molecules c. Hyphae i. Tubular cell walls that contain chitin (found in insect exoskeletons) ii. Septa divide cells iii. Fungi w/o septa are coenocytic iv. Mycelium – Interwoven mass of hyphae d. Diverse lifestyles: i. Saprobic (decomposers) ii. Parasitic 1. Haustoria – hypha to penetrate host tissues. Ex: Arthrobotrys on nematode iii. Mutualistic 1. Mycorrhizae – “fungus roots” a. Ecto – hyphae form on root surface b. Endo – extend hyphae through root cell wall c. Plant obtains nutrients (Phosphorus, nitrogen, minerals) while fungus obtains organic compounds (photosynthate) Ex: Soybean 3. What are structural components of fungi, including hyphae, haustoria, septa, mycelia? a. See above 4. What are mycorrhizal associations? Endomycorrhizae? Ectomycorrhizae? a. See above 5. What are the key aspects of the asexual and sexual life cycles of fungi? Plasmogamy and kayrogamy? Haploid and diploid phases? a. Sexual reproduction: i. Hyphae from 2 distinct mycelia emit pheromones ii. If different mating types, hyphae will fuse iii. Union of cytoplasm is called plasmogamy iv. Mycelia are now heterokaryotic (“different nuclei”) v. In some fungi, haploid nuclei pair off to form a dikaryotic (“two nuclei”) mycelium vi. Time passes vii. Union of haploid nuclei is called karyogamy (diploid zygote is produced) viii. Meiosis produces spore-producing structures (haploid) b. Asexual reproduction: i. Spores germinate, form mycelia ii. Mycelia produce spore-producing structures iii. Spore germinate, cycle repeats iv. All structures are haploid
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v. Most common in: 1. Molds 2. Yeasts: simple cell division or “budding” (small portion of parent cell pinches off) 6. What kingdom is most closely related to Fungi? a. Animal kingdom, descended from an aquatic, single-celled, flagellated protist 7. Know the five phyla of fungi, what are their distinguishing features, the approximate number of species, what nutritional role(s) they play, and be able to recognize or recall examples of species from each phylum. a. Chytridiuomycota – Chytrids i. 80 species known ii. Mostly saprobes and parasites in aquatic habitats iii. Earliest to diverge iv. Ex: Amphibian chytrid – invades skin, affects ability of frog to regulate exchange of water and oxygen with environment. v. Have flagellated spores (zoospores) vi. Flagella seem to have been lost on more than one occasion during the evolution of fungi vii. Paraphyletic with… b. Zygomycota – Zygote fungi i. 1000 species ii. Coenocytic iii. Sexual – zygosporangium (dormant phase) 1. karyogamy and then meiosis occure 2. is a multinucleate structure, first heterokaryotic with many haploid nuclei from 2 parents, then with many diploid nuclei after karyogamy 3. metabolically inactive, resistant to freezing and drying iv. Asexual – common v. Mostly terrestrial vi. Ex: Fruit molds, black bread mold, etc.
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