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
View Full Document