TAMU BIOL 112 - CH31 (4 pages)

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CH31



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CH31

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Pages:
4
School:
Texas A&M University
Course:
Biol 112 - Introductory Biology Ii
Introductory Biology Ii Documents

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Chapter 31 Fungi Characteristics Fungus feeding body is the mycelium o Made up of branching filamentous thread like Hyphae 31 2 Often unseen underground or within the host o 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 continuous o Rapid growth at hyphal tips toward new food no motile feeding cells o Huge total surface area for absorbption o 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 spores o 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 Unicellular o Live in water films or moist tissue Fungus Reproduction Spores n made in both sexual and asexual cycles o Dispensed by air and water to new resources Spores germinate if they land on food and water o Each grows into a new haploid mycelium Sexual cycles make no gametes o No genders instead plus or minus mating types o 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 animals o Zygote 2n always does meiosis immediately after forming making genetically diverse spores n Fungi never have a multicellular 2n stage o Fig 31 5 KNOW for test Asexual cycles common 31 13 17 o Making genetically identical spores and mycelia Growths like this are called mold o Single cell yeasts bud off new daughter cell by mitosis o Fragments of mycelium can grow



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