Lecture 1 03 06 2013 Fungi are related to animals Evolved from a unicellular Protist ancestor that had a flagellum Opisthokonts o Animals o Fungi o Choanoflagellates Flagellum o Usually singular and postier o Sometimes flagella is only temporary o Within the human group Fungi flagellated ancestor related to choanoflagellates Defining feature is absorptive heterotrophy and chitin in cell walls o Absorptive heterotrophy Secrete digestive enzymes outside their bodies to break down large food molecules in their environment Absorb the breakdown products through plasma membrane of cell walls Conceivable in ALL ENVIRONMENTS Absorb nutrients from dead organic matter Absorb nutrients from living hosts o Saprobes o Parasites o Mutalists Intimate associations with other organisms that benefit both partners Fungi are made up of 6 major groups Ascomycota o Terrestrial o Sac fungi o Monophyletic o Sexual reproductive saclike structure ascus contains haploid ascospores o Perforated septa o Dikaryon Basidiomycota o Terrestrial o Monophyletic o Club fungi o Sexual reproductive structure basidium swollen cell at the tip of a specialized hypha that supports haploid basidiospores o Perforated septa o Dikaryon Unicellular fungi are called yeasts Yeast unicellular fungus o Zygospore fungi sac fungi club fungi Most fungi are multicellular yeast are the exception Some fungi have yeast stages that include a filamentous stage Used to make bread and beer Lifestyle Yeast refers to a lifestyle not a taxonomic group o Spend time doing asexual reproduction o Aquatic and moist environment o Absorb nutrients directly across cell surfaces o Fission split cell evenly o Budding smaller bit buds off of it that is smaller and will eventually grow into a full sized cell Yeasts are not monophyletic Easy to study can be cultured and grow rapidly o Have genomic structure similar to humans and other Multicellular fungi are composed of hyphae Mycelium body of a multicellular fungus o Composed of a mass of individual tubular filaments called eukaryotes hyphae Long filament Cytoplasm surrounded by cell wall Cell wall made of chitin Start and end isn t defined by cell wall or cell membrane All of the hyphae together are mycelium Rhizoids Modified hyphae Anchor cells to their substratum dead organism or other matter on which they feed Not homologous to the rhizoids of plants Not specialized to absorb nutrients and water Parasitic fungi May possess modified hyphae that take up nutrients from their host Septa subdivide the hyphae into cell like compartments by INCOMPLETE cross walls do not completely close off compartments in the hyphae gaps known as pores allow organelles like nuclei to move in a controlled way between compartments Multicellular multinuclear Fungus with septum septate Fungus without septum coenocytic One filament full of all the cytoplasm nuceli and organelles Results from repeated nuclear divisions without cytokinesis Dikaryon o 2 nuclei are there but they don t fuse together o Come as a result of sexual reproduction o n n o Singular hypha has 2 genetically distinct nuclei Fungi are in intimate contact with their environments Mycelium secretes enzymes throughout the soil around them Hyphae and filaments are spread out throughout the soil lots of surface area o Do more work absorb more food o Helps with absorptive heterotrophy o Myceium except fruiting body is close to their environmental source for food o Large surface area water loss Need moist environment o Hypertonic environments Can live in environments with solute concentrations higher than their own More resilient than bacteria in hypertonic environments o Tolerance of extreme temperatures May clump together in a cottony mass to exploit a rich nutrient source Enzymes break down organic molecules and absorb them Secrete all enzymes and digesting what is around them Fruiting body o Occurs when sexual spores are produced o Mycelium reorganizes into a reproductive fruiting body mushroom o Mycelial mass is larger than the mushroom roots and underground mycelium Fungal cells have more than one nucleus Nuclei work their way through holes in septa No nuclear envelope that dissolves Lack a lot of the cytoskeleton o No centrioles o No cytokinesis keep nuclei in one packet Plasmogamy hyphae together Nuclei don t fuse 2 nuclei per section of hypha Fungi reproduce asexually and sexually DRAW CYCLE Asexual reproduction o When 2 come in contact with one another can fuse their o Production of usually haploid spores in structures called sporangia o Production of haploid spores not enclosed in sporangia at the tips of hyphae spores called conidia o Cell division by unicellular fungi Equal division of one cell into two Fission Asymmetrical division in which a daughter cell is produced Budding o Simple breakage of the mycelium o Can produce large amounts of spores o Make spores by mitosis o Make sporangium make spores over and over again Sexual Reproduction o Rare o No morphological distinction between male and female structures or male and female individuals o Mating types Genetically determined distinction Individuals of the same mating type can t mate with one another One mating type can mate with another mating type within the same species Prevents self fertilization Differ genetically Visually and behaviorally indistinguishable Also found in protists o Hypahe or motile cells of different mating types meet and fuse o Zygote nuclei formed by sexual reproduction are the only diploid nuclei in the life cycle o Nuclei go through mitosis produce haploid nuclei that become incorporated into spores o Haploid fungal spores whether produced sexually or asexually germinate and their nuceli divide mitotically to o Mating types come together fuse their cytoplasm through produe haploid hyphae plasmogamy o Produces a new mycelium that is n n Dikaryotic o Karyogamy Eventually the nuclei fuse together fertilization Kary nucleus o Fusion makes the it diploid o Zygote can undergo meiosis and produce spores which is where the process starts again o Sometimes the fungi just remain n Fungi can be saprobes Saprobic consume nonliving organic matter Along with bacteria major decomposers on earth o Contribute to decay and recycle the elements on earth used by living things o Principle decomposers of cellulose and lignin main components of cell walls o Decompose keratin break down animal structures like hair and nails Global carbon cycle o Carbon is taken into living things from inorganic