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What are characteristics that distinguish fungi from organisms in other kingdoms?
- nutrition
- structural organization
- growth and reproduction
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How do fungi acquire their nutrients?
- Fungi secrete hydrolytic enzymes and acids to decompose complex molecules into simpler ones that can be absorbed.
- Saprobes (decomposers)
- Parasites
- Mutualistic fungi
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How do non-motile fungi seek new food sources and how do 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.
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What is the basic body plan of a fungus?
- They have hyphae that make up the mycelium (the underground part of the fungus).
- They are composed of “chitin” (a nitrogen-containing polysaccharide).
- Hyphae provide a large surface area with which to increase absorption.
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What is the difference between septate and aseptate (coenocytic) fungi?
- Septate fungi are divided into cells by crosswalls called septa – pores allow organelles to move around.
- In aseptate fungi, hyphae lack crosswalls and are coenocytic (formed form repeated nuclear division without cytokinesis).
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What is syngamy?
- Syngamy is the sexual union of haploid cells (2 phases)
- 1.Plasmogamy (the fusion of cytoplasm)
- 2.Karyogamy (the fusion of nuclei)
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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.
- One haploid genome may compensate for harmful mutations in the other nucleus.
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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
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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
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Explain the difference between conidia and ascospores.
- 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)
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Explain why ascomycetes can be useful to geneticists studying genetic recombination.
- They are found in marine, freshwater, and terrestrial habitats.
- 1.Plasmogamy gives rise to dikaryotic hyphae and the tips become asci.
- 2.Karyogamy combines the parental genomes and meiosis forms genetically varied ascospores.
- 3.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.
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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
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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
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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
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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
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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
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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
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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
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