CHAPTER 31 FUNGI

I. INTRODUCTION TO FUNGI FUNGI ARE STRUCTURALLY AND NUTRITIONALLY DISTINCTIVE EUKARYOTES. MOST ARE MULTICELLULAR.

A.     ABSORPTIVE NUTRITION ENABLES FUNGI TO LIVE AS DECOMPOSERS AND SYMBIONTS ALL FUNGI ARE HETEROTROPHS (DECOMPOSERS SYMBIONTS), ACQUIRING THEIR NUTRIENTS BY ABSORPTION.

A.     EXTENSIVE SURFACE AREA AND RAPID GROWTH ADAPT FUNGI FOR ABSORPTIVE NUTRITION THE VEGETATIVE BODIES OF FUNGI CONSIST OF MYCELIA, NETLIKE COLLECTIONS OF BRANCHED HYPHAE ADAPTED FOR ABSORPTION. PARASITIC FUNGI PENETRATE THEIR IS WITH SPECIALIZED HYPHAE CALLED HAUSTORIA. MOST FUNGI HAVE CELL WALLS MADE OF CHITIN. ALTHOUGH ASEPTATE (COENOCYTIC) FORMS OCCUR, MOST FUNGI HAVE THEIR HYPHAE PARTITIONED INTO CELLS BY SEPTA, WITH PORES ALLOWING CELL-TO-CELL CONTINUITY.

C. FUNGI REPRODUCE BY RELEASING SPORES THAT ARE PRODUCED EITHER SEXUALLY OR ASEXUALLY FUNGI PRODUCE REPRODUCTIVE STRUCTURES (SPORES) BY SEXUAL AND ASEXUAL MEANS. THE SEXUAL CYCLE INVOLVES CELL FUSION (PLASMOGAMY) AND NUCLEAR FUSION (KARYOGAMY), WITH AN INTERVENING DIKARYOTIC STAGE (WITH TWO HAPLOID NUCLEI). THE DIPLOID PHASE IS SHORT-LIVED AND RAPIDLY UNDER- MEIOSIS TO PRODUCE HAPLOID SPORES.

II. DIVERSITY OF FUNGI

CHYTRIDS ARE FUNGI THAT RETAIN A FLAGELLATED CONDITION; A.     DIVISION CHYTRIDIOMYCOTA: CHYTRIDS MAY PROVIDE CLUES ABOUT FUNGAL ORIGINS CHYTRIDS ARE FUNGI THAT RETAIN A FLAGELLATED CONDITION; THEY MAY REPRESENT A LINK BETWEEN THE FUNGAL KINGDOMS AND THE PROTISTS

A.     DIVISION ZYGOMYCOTA: ZYGOTE FUNGI FORM RESISTANT DIKARYOTIC STRUCTURES DURING SEXUAL REPRODUCTION ZYGOTE FUNGI, SUCH AS THE BLACK BREAD MOLD, ARE NAMED FOR THEIR SEXUALLY PRODUCED ZYGOSPORANGIA, WHICH ARE DIKARYOTIC STRUCTURES CAPABLE OF PERSISTING THROUGH UNFAVORABLE CONDITIONS.

C. DIVISION ASCOMYCOTA: SAC FUNGI PRODUCE SEXUAL SPORES IN SACLIKE ASCI SEXUAL REPRODUCTION IN THE FUNGI INVOLVES THE FORMATION OF SPORES IN SACS, OR ASCI, AT THE ENDS OF DIKARYOTIC HYPHAE, USUALLY IN ASCOCARPS.

E. MOLDS, YEASTS, LICHENS, AND MYCORRHIZAE REPRESENT UNIQUE LIFESTYLES THAT EVOLVED INDEP. IN 3 FUNGAL DIVISIONS MOLDS ARE RAPIDLY GROWING, ASEXUALLY REPRODUCING FUNGI THAT ARE IMPORTANT IN THE COMMERCIAL PRODUCTION OF ANTIBIOTICS, SUCH AS PENICILLIN. YEASTS ARE UNICELLULAR FUNGI ADAPTED TO LIFE IN LIQUIDS SUCH AS PLANT SAPS. LICHENS ARE SUCH HIGHLY INTEGRATED SYMBIOTIC ASSOCIATIONS OF ALGAE AND FUNGI THAT THEY ARE CLASSIFIED AS SINGLE ORGANISMS. MYCORRHIZAE ARE MUTUALISTIC ASSOCIATIONS OF FUNGI WITH THE ROOTS OF VASCULAR PLANTS.

III. ECOLOGICAL IMPACTS OF FUNGI ECOSYSTEMS DEPEND ON FUNGI AS DECOMPOSERS AND SYMBIONTS WITHOUT FUNGI AND BACTERIA AS DECOMPOSERS, BIOLOGICAL COMMUNITIES WOULD BE DEPRIVED OF THE ESSENTIAL RECYCLING OF CHEMICAL ELEMENTS BETWEEN THE BIOLOGICAL AND NONBIOLOGICAL WORLD. FUNGI ARE PARTICULARLY IMPORTANT DECOMPOSERS OF WOOD. FUNGI ALSO DECOMPOSE FOOD AND OTHER USEFUL OBJECTS.

B. SOME FUNGI ARE PATHOGENS SOME FUNGI CAUSE DISEASE, HARMING HUMANS WITH A VARIETY OF ILLS. PLANTS ARE ESPECIALLY VULNERABLE TO FUNGAL INFECTIONS

C. MANY ANIMALS, INCLUDING HUMANS, EAT FUNGI

IV. PHYLOGENETIC RELATIONSHIPS OF FUNGI A.     FUNGI AND ANIMALS PROBABLY EVOLVED FROM A COMMON PROTISTAN ANCESTOR MOLECULAR EVIDENCE SUPPORTS THE HYPOTHESIS THAT FUNGI AND ANIMALS DIVERGED FROM A COMMON ANCESTOR, PROBABLY A FLAGELLATED AQUATIC PROTIST.

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