Chapter 31: Fungi
Chapter 31: Fungi BYS 120
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This 6 page Class Notes was uploaded by Amelia Notetaker on Tuesday December 1, 2015. The Class Notes belongs to BYS 120 at University of Alabama - Huntsville taught by Dr. Luciano Matzkin in Fall 2015. Since its upload, it has received 94 views. For similar materials see Organismal Biology in Biological Sciences at University of Alabama - Huntsville.
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Date Created: 12/01/15
Chapter 31 Lecture Notes Fungi o Over 100,000 described species Fungal ecology o Heterotrophs o Use enzymes to break down complex molecules into smaller organic compounds o These enzymes are very versatile, which contributes to fungi's ecological success o Can be Decomposers Parasites Mutualists Predatory General structure of fungi o Most uncommon body structure are multicellular filaments and single cells (yeast) o Some species grow as either filaments or yeasts; others grow as both o The morphology of multicellular fungi enhances their ability to absorb nutrients o Consist of mycelea, networks of branched hyphae adapted for absorption o Mycelluim's structure maximizes its surface area-to-volume ratio Hyphae o Cell walls contain chitin o Most fungi have hyphae divided into cells by septa, with pores allowing cell-to-cell movement of organelles o Septate hyphae o Coenocytic fungi lack septa o Have continuous cytoplasmic mass with 100's or 1000's of nuclei Hyphae of fungal mutualists o Mycorrhizal fungi have a mutualistic relationships with plants o Have specialized hyphae called haustoria that allow them to penetrate the tissue of their host General like cycle of fungi o Fungi propagate themselves by producing vast number of spores either sexually or asexually o Fungi can produce spores from different spores from different types of life cycles Asexual reproduction o Many can reproduce sexually Only some o Molds produce haploid spores by mitosis and form visible mycelia Bread mold o Some yeasts can reproduce asexually or sexually Depend on conditions o Single cell fungi o Asexually reproduce by simple cell division and the pinching of "end cells" from a parent cell Sexually reproduction o Normally haploid with exception of transient diploid stages formal during sexual life cycles o Requires fusion of hyphae or cells from different mating types o Use sexual signaling molecule (pheromones) to communicate mating type o Under appropriate conditions when cell from different mating types meet they will fuse o Plasmogamy: union of cytoplasm from 2 parent mycelia Not fusion of nuclei o In most fungi the haploid nuclei from each parent don't fuse right away, they coexist in the mycelium Heterokaryon o In some fungi the haploid nuclei pan off to a cell, such as mycelium is said to be dikaryotic Life cycles o Diploids can only go through meiosis During karyogamy, the haploid fuse, producing diploids Long time can pass until fusion o Diploid is short lived and undergoes meiosis producing haploid spores o Paired processes of karyogamy and meiosis produce genetic variation Fungal evolution o Oldest fossils only 460 MYA o Molecular analysis suggests fungal/animal split was about 1 BYA o Microsporidia: spore producing unicellular parasites of animals and protists o Tiny organelles derived from mitochondria but not conventional mitochondria o Basis of fungi today o Fungi were earliest colonies of land and probably formed mutualistic relationships with protists and early land plants "-cetes" suggest fungi When does meiosis occur in fungi? o Following fusion of nuclei Chytrids o Found in fresh water and terrestrial o Decomposers, parasites, and mutualists o Supports hypothesis emerged early in evolution o Unique because they have flagellated spores Zoospores o Batrachochytrium dendrobatidis might be causing recent decline in amphibians Zygomycetes o Exhibits great diversity o Produce sexually --> zygosporangia Site of karyogamy and meiosis Resistant to freezing and drying and survive unfavorable conditions o Black bread mold Hyphae are coenocytic o Sexual reproduction o Pilobolus can aim sporangia toward conditions associated with good food sources Glomeromycetes o Form arbuscular mycorrihizae Hyphae "sneaks" into cells and get through cell walls (not membrane) then grows a small tree-like structure against the membrane of the plant o Ectomycorrihizal Grows hyphae over a root and into extra cellular spaces of root cortex Related to bacteria that fix N2 Asocomycetes o Live in marine, fresh water, and terrestrial o Sac-like asci contained in fruiting bodies called ascocarps Also called sac fungi o Form unicellular yeasts and cup fungi and molds o Plant pathogens, decomposers, symbionts, and predatory o Arthobotys Predatory Use pheromones and hyphae shaped as a loop. Pheromones attract organisms who get excited because of the smell, the organism swims into the loop and is strangled then decomposed by enzymes o Reproduce asexually with conidia Basidomycetes o Include mushrooms o Club-like structures (basidium) transient diploid stag in life cycle Called club fungi o Many are decomposers o Long-lived dikaryotic mycelium o Mycelium reproduces sexually by producing fruiting body (basidiocarps) o Numerous basidia in BC are sources of sexual spores called basiospores You have several unknown organisms and you think one is a fungus, how do you determine if it is or not? o Presence of chitinous cell wall Animals that have diploid cells and attract a mate. What life stage does a fungus accomplish this? o Haploid hyphae Fungus farming o Leaf-cutter ants don't eat the leaves Chop plants up and bring to nest Brings to a fungus garden in nest that feeds on this and decompose the plant matter The ants then trim the fungi so it always feels as if it is in a good environment Some of these fungi are only found in association with ants Ecological importance: decomposers o Efficient decomposition of organic material Cellulose and lignin o Perform recycling Mutualists o Mycorrihizae o Ants o Lichens Symbiotic association between photosynthetic microorganisms and fungi Millions of photosynthetic cells held in fungal hyphae Pathogens o 30% of known species are parasitic or pathogens Mostly for plants o Human fungal pathogens Ring worm (athlete's foot) Vaginal yeast infections Predators o Arthrobotrys
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