Chapter 31 Reading Quiz What are the filaments called that make up mycelium? What are fungi cell walls made of? What characteristic does “dikaryotic” refer to? The symbiotic relationship between a green alga & a fungus is called… About what % of the 100,000 fungus species are parasitic?

1. List characteristics that distinguish fungi from organisms in other kingdoms. Fungi are very different They differ in: 1. Nutrition 2. Structural organization 3. Growth and reproduction 

2. Explain how fungi acquire their nutrients. They secrete hydrolytic enzymes and acids to decompose complex molecules into simpler ones that can be absorbed Saprobes Parasites Mutualistic fungi 

3. Explain how non-motile fungi seek new food sources and how they disperse. Through extensions of hyphae that can grow up to a kilometer total per day Parasitic fungi have “haustoria” which penetrate a host for nutrition 

4. Describe the basic body plan of a fungus. Hyphae  make up the mycelium (the underground part of the fungus) Composed of “chitin” (a nitrogen-containing polysaccharide) Hyphae provide a large surface area with which to increase absorption 

5. Distinguish between septate and aseptate (coenocytic) fungi.  Divided into cells by crosswalls called septa – pores allow organelles to move around Aseptate  Hyphae lack crosswalls and are coenocytic (formed form repeated nuclear division without cytokinesis) 

Terms to know… Syngamy  sexual union of haploid cells (2 phases) Plasmogamy  the fusion of cytoplasm Karyogamy  the fusion of nuclei

6. Describe some advantages to the dikaryotic state. After plasmogamy, haploid nuclei from each parent pair up forming a dikaryon, but they do not fuse Nuclear pairs in dikaryons may exist and divide synchronously for months or years Advantages  one haploid genome may compensate for harmful mutations in the other nucleus 

7. Distinguish among fungi and list some common examples of each. Chytridiomycota  chytrids Zygomycota  mycorrhizae, Rhizopus Ascomycota  yeasts, cup fungi, septate hyphae Basidiomycota  club fungi, mushrooms, shelf fungi, puffballs 

8. Describe asexual and sexual reproduction in Zygomycota, Ascomycota, and Basidiomycota, and the sexual structure that characterizes each group. Zygomycota  zygote fungi form resistant dikaryotic structures during sexual reproduction (sporangia) Ascomycota  asexual: form conidia, sexual: form ascospores in an ascus Basidiomycota  asexual: not common and result in conidia, sexual: form basidiocarps 

9. Explain the difference between conidia and ascospores. Ascomycota  Conidia – tips of specialized hyphae, haploid, spores for wind dispersal (asexual) Ascospores – haploid mycelia of opposite mating strains fuse and develop spores within an ascus (sexual) 

Zygomycota, Ascomycota, Basidiomycota, Chytridiomycota

10. Explain why ascomycetes can be useful to geneticists studying genetic recombination. They are found in marine, freshwater, and terrestrial habitats Plasmogamy gives rise to dikaryotic hyphae and the tips become asci Karyogamy combines the parental genomes and meiosis forms genetically varied ascospores In many asci, 8 ascospores are lined up in a row in the order in which they formed from zygote This arrangement provides geneticists with an opportunity to study genetic recombination – differences reflect crossing over and independent assortment of chromosomes during meiosis 

11. Explain why the Deuteromycota are called imperfect fungi. These are the molds with no known sexual stages Reproduce asexually by producing spores Provide a source for antibiotics for humans 

12. Describe the anatomy of lichens and explain how they reproduce. These are highly integrated symbiotic associations of algal cells (usually filamentous green algae or cyanobacteria) with fungal hyphae (usually ascomycetes) Alga is located below the lichen’s surface and provides food for fungus and may fix nitrogen Fungus provides suitable environment and protection for algae and absorbs minerals, water 

13. Provide evidence for both sides of the debate on whether symbiosis in lichens is parasitic or mutualistic. Mutualism – fungi benefit the algae and lichens can survive in habitats that are inhospitable to either organism alone “controlled” parasitism – fungi actually kills some algal cells, though not as fast as algae replenishes itself 

14. Describe the ecological importance of lichens. They are important pioneers – break down rocks and allow colonization by other plants Can tolerate severe cold Photosynthesis occurs when lichen water content is 65 – 75% Lichens are sensitive to air pollution due to mode of mineral uptake – provide a good idea of how polluted an area is 

15. Explain why fungi are ecologically and commercially important. Fungi and bacteria are the principal decomposers on earth Fungi also are pathogens  athlete’s foot, ringworm, yeast infections, plant infections 10 – 50% of the world’s fruit harvest is lost yearly due to fungal infections 

16. Describe how the mutualistic relationship in mycorrhizae is beneficial to both the fungus and the plant, and explain its importance to natural ecosystems and agriculture. Mycorrhizae  specific mutualistic associations of plant roots and fungus Fungi increases the absorptive surface of roots and exchanges soil minerals mycorrhizae are seen in 95% of all vascular plants; they are necessary for optimal plant growth and function 

17. Describe a scenario for fungal phylogeny and list two possible ancestors of Zygomycota. Fungi and animals probably evolved from a common protist ancestor Molecular evidence supports that the four fungal divisions are monophyletic (flagellated cells, etc) Flagella are lost in the chytrid lineage to Zygomycota 