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TAMU BIOL 112 - CH31

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Chapter 31 FungiCharacteristics- Fungus feeding body is the myceliumo Made up of branching filamentous thread-like Hyphae (31.2) Often unseen: underground or within the hosto Hyphae secret hydrolytic enzymes and acids This digests organic materials Simple organic molecules are absorbed- Thus fungi are absorptive heterotrophs- Hyphae are made of tubular cells (like a network of pipes)o Rigid cell walls with chitin (also in insect exoskeletons)o Multicellular: septate or coenocytic hyphae Both allow rapid cytoplasmic streaming Septate= thin dividing walls between cells Coenocytic= all continuouso Rapid growth at hyphal tips toward new food (no motile feeding cells)o Huge total surface area for absorbptiono Some specialized hyphae (31.4) Haustoria penetrate cell walls (BUT NOT the membrane) of host plants Some hyphae catch nematodes for the N- Reproductive bodies make sporeso Usually above ground and therefore what we notice Fairy rings= 1 organism mycelium spread out, reproduction at the most active places- Some fungi are yeasts (31.7)o Unicellularo Live in water films or moist tissueFungus Reproduction- Spores (n) made in both sexual and asexual cycleso Dispensed by air and water to new resources- Spores germinate if they land on food and watero Each grows into a new haploid mycelium- Sexual cycles make no gameteso No genders, instead plus or minus mating typeso 3 steps to form the zygote Plasmogomy=fusion of plus and minus hyphae Heterokaryotic stage= hyphae with unfused haploid nuclei of both types Karyogomy= fusion of haploid nuclei to form a zygote (2n)o Plasmogomy and karyogomy are equivalent to fertilization in animalso Zygote (2n) always does meiosis immediately after forming, making genetically diverse spores (n) Fungi never have a multicellular 2n stageo Fig 31.5-KNOW for test- Asexual cycles common (31.13, .17)o Making genetically identical spores and mycelia Growths like this are called moldo Single cell yeasts bud off new daughter cell by mitosiso Fragments of mycelium can grow into a new individualOrigin of Fungi- Share unicellular flagellated ancestor with animalso Multicellularity evolved independently- Land invasiono Oldest fungi fossils are about 460 mya (terrestrial)o Lichen like fossils date even oldero Earliest plant roots also had mycorrhizaePhylogeny- Aquatic, Flagellao Chytrids- Terrestrial, No flagellao Zygomycesteso Glomeromyceteso Ascomyceteso BassidiomycetesImportance of Fungi- Fungi are Decomposerso Break down dead tissue (including ligin)= Especially wood Only second to bacteria in importanceo Damage property Dry rot, wet rot, mold and mildew- Fungi are mutulaistso Mycorrhizae (37.13) Fungi living in close association with almost all plant roots Mycorrhizal fungi help plant absorb moisture and minerals Fungi gets sugars, ect. from the planto Lichen (31.23,.24) Fungi living in close associate with photosynthetic unicellular chlorophyte/cyanobacteria Fungus “gives” frame work, moisture, and minerals Algae/cyanobacteria give sugar Can reproduce as dual organisms via Soredia Key pioneer organisms on bare rock and harsh environments- Create soil for plants which lead to food for animalso Fungus-gardening ants (31.22) Leaf-cutting ants provide food and are to fungus wicch the eat- Fungi are pathogenso Infecting plants Attack trees, landscape plants, crops Rusts and smuts Ergot on barley and rye, ergotism LSD (31.25) Various molds Aspergillus mold in peanuts Pink ear mold in corno Infecting animals Chytria causing a huge decline in amphibian populations Zombie ants caused by Ascomyceteo Humans Mycosis is infection due to fungus Some are very serious and difficult to treat- Ex=recent meningitis from steroid shots Many are common and treatable- Ex=ringworm, athlete’s foot, jock itch, and vaginal yeast infection- Benefit medicine and researcho Source of antibiotics and other drugs Ex=penicillin (31.27)o Genetic reseach and biotechnology Ex= Neurospora, a research model organism, yeasts- Fungi and foodo Humans eat ito Truffleso Yeast fermentation CO2 for rising bread Ethyl alcohol in beer and wineo Molds used in food processing Ex=Beer, cheese, soy sauce- Poisonous fungio Many mushrooms are deadlyo Never eat wild fungiLargest organisms are


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TAMU BIOL 112 - CH31

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