Jim Bidlack bio 1304 general botany lecture 28 Lower Fungi I. Characteristics of the "(lower) fungi"




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Jim Bidlack - BIO 1304
GENERAL BOTANY Lecture 28 - Lower Fungi
I. Characteristics of the "(lower) fungi"

  1. IMPORTANCE: decomposition, disease, symbiotic relationships

  2. Heterotrophic, eukaryotic, lack photosynthesis, reproduce by spores

II. Flowering plants vs. "fungi"

A. Flowering plants (SPOROPHYTES) produce haploid spores by meiosis - called MEIOSPORES

B. "Fungi" (MAIN UNIT IS MYCELIUM: composed of hyphae) have sporangia which produce "SPORES"

1. Spores from fungi are asexually reproductive structures that can develop into an adult "PLANT" without gametic fusion

  1. Less sophisticated "fungi" that may be considered as members of Kingdom Mycota

** NOTE: SOMETIMES THESE ORGANISMS ARE CLASSIFIED IN KINGDOM PROTISTA **

A. Phylum Dictyosteliomycota

1. Sometimes referred to as Phylum Myxomycota (slime molds)

a) "Animal" characteristics

1) Main unit (chitin wall) is called a plasmodium

a)) Shows amoeboid movement

b)) Can take in solid food

b) Fungus because of spores in sporangia

c) Life cycle - amoeba-like w/spores ==> meiosis, spores germinate, live, fuse, and repeat cycle

B. Phylum Oomycota

1. Sometimes referred to as the water molds

a) Produce egg cells during sexual reproduction

b) Produce swimming flagella

c) Vegetative body (mycelium) is cellulose

d) Life cycle

1) Asexual: sporangia, spores (zoospores), hypha, mycelium

2) Sexual: hyphae specialize to become oogonia & antheridia, "mate," zygote becomes an oospore

  1. Examples: Phytophthora infestans (potato blight)

IV. Kingdom Mycota - the REAL FUNGI - never motile, always chitinous walls

**NOTE: USUALLY CLASSIFIED IN KINGDOM MYCOTA**

Most fungal bodies composed of filaments called hyphae; many hyphae make mycelium

A. Phylum Zygomycota (zygote fungi)

1. Hyphae have no cross walls between nuclei

2. Reproduce asexually by spores in sporangia or sexually by production of zygospores

3. Asexual: sporangia on tips of hyphae, haploid spores formed by mitosis

  1. Sexual: hyphae specialized to become "+" and "-," zygote becomes a zygospore,

zygospore sits around until it is time to undergo meiosis, meiosis produces a new sporangium (on hypha)

5. Most are saprophytes and attack stored foods

B Phylum Ascomycota (sac fungi) - HIGHER FUNGI BEGIN HERE (BECAUSE OF COMPLEXITY)

1. Mycelium is divided into cells by cross-walls (septate hyphae)

2. Each hypha contains one haploid nucleus

  1. Reproduce asexually by conidia or sexually by fusion of haploid hyphae of different

strains

  1. Asexual: spores produced mitotically at tips of aerial hyphae (conidiophores) to

produce conidia

  1. Sexual: fusion of different hyphae, nuclei pass from one to the other to make an

"N + N" (dikaryotic) cell (ascoma), ascogenous hyphae grow and branch and then

make asci at tips of hyphae, fusion of nuclei follows meiosis, then mitosis to yield

eight haploid ascospores

  1. Examples: powdery mildew, Dutch elm disease, chestnut blight, ergot poisoning,

and yeasts (which also do "budding")


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