BIOL 1030 – TOPIC 3 LECTURE NOTESTopic 3: Fungi (Kingdom Fungi – Ch. 31)KINGDOM FUNGIA. General characteristics- Fungi are diverse and widespread.- Ten thousand species of fungi have been described, but it is estimated that there are actually up to 1.5 million species of fungi.- Fungi play an important role in ecosystems, decomposing dead organisms, fallen leaves, feces, and other organic materials.- This decomposition recycles vital chemical elements back to the environment in forms other organisms can assimilate.- Most plants depend on mutualistic fungi to help their roots absorb minerals and water from the soil.- Humans have cultivated fungi for centuries for food, to produce antibiotics and other drugs, to make bread rise, and to ferment beer and wine- Fungi play ecological diverse roles - they are decomposers (saprobes), parasites, and mutualistic symbionts.- Saprobic fungi absorb nutrients from nonliving organisms.- Parasitic fungi absorb nutrients from the cells of living hosts. Some parasitic fungi, including some that infect humans and plants, are pathogenic. Fungi cause 80% of plant diseases.- Mutualistic fungi also absorb nutrients from a host organism, but they reciprocate with functions that benefit their partner in some way.- Fungi are a monophyletic group, and all fungi share certain key characteristics.B. Morphology of Fungi1. heterotrophs - digest food with secreted enzymes “exoenzymes” (external digestion)2. have cell walls made of chitin3. most are multicellular, with slender filamentous units called hyphae (Label the diagram below – Use Textbook figure 31.3)1 of 12BIOL 1030 – TOPIC 3 LECTURE NOTES Septate hyphae Coenocytic hyphaehyphae may be divided into cells by crosswalls called septa; typically, cytoplasm flows through septa- hyphae can form specialized structures for things such as feeding, and even for food capture4. Mycelium - interwoven mat-like network of hyphae filaments can be packed tightly together (ex: mushroom)mycelia can be huge, but they usually escape notice because they are subterranean.visible parts usually reproductive structures – mushrooms, morels, etc.5. Haustoria are specialized hyphae that penetrate cells (for feeding or other purposes)6. Most furngi have nuclear mitosis (nuclear membrane remains intact during mitosis)7. No motile stages for most (no swimming cells – lack cilia and flagella)C. Fungal Reproduction1. reproduce by spores - sexual spores are meiospores (formed by meiosis)- asexual spores are mitospores (formed by mitosis)2 of 12BIOL 1030 – TOPIC 3 LECTURE NOTES2. sexual reproduction for most by zygotic meiosis, but sometimes in a weird way- haploid phase predominates- BUT, syngamy (fertilization) has 2 steps plasmogamy: union of gamete cells karyogamy: union of gamete nuclei- some fungi do plasmogamy but delay karyogamy, forming cells that each have two separate haploid nuclei; these hyphae are called dikaryotic - example of fungal life cycle with dikaryotic hyphae: mushroom dikaryotic mycelium is major phase only when mushroom is formed does karyogamy occur, followed by meiosisComplete the life cycle to explain the generalized life cycle of fungi (use textbook Figure 31.5):3 of 12BIOL 1030 – TOPIC 3 LECTURE NOTESD. Fungal phylogeny  Five phyla plus "imperfect fungi" phyla separated mainly by how meiospores are formed (how sexual reproduction done) 1. Phylum Chytridiomycota – chytrids2. Phylum Zygomycota – zygomycetes3. Phylum Glomeromycota – glomeromycetes4. Phylum Ascomycota – ascomycetes; sac fungi5. Phylum Basidiomycota – basidiomycetes; club fungi6. imperfect fungi (also known as deuteromycetes) Kingdom Fungi forms a clade with Kingdom Animalia, choanoflagellates, and perhaps others What Kingdom is Fungi a sister kingdom to ? last common ancestor between Fungi and Animalia apparently about 670 million years ago (MYA) basal fungal group for Fungi appears to be Chytridiomycota, which is likely paraphyletic phylogeny of Zygomycota uncertain; likely paraphyletic, perhaps polyphyletic Glomeromycota is monophyletic, and also forms a clade with Ascomycota and Basidiomycota Ascomycota and Basidiomycota form a clade, and each is monophyletic itself Aside – for modern cladograms see the Tree of Life online: http://tolweb.orgFill in the phyla names (Textbook Fig. 31.9 )4 of 12BIOL 1030 – TOPIC 3 LECTURE NOTESD.1. Phylum Chytridiomycota – chytrids apparently paraphyletic motile zoospores – only fungi with flagella (thus only fungi with true motility) primarily aquatic (rest of fungi are primarily terrestrial) likely either a sister group to other fungi or a paraphyletic basal assemblage■ fossils resembling modern chytrids date back as far as about 400 MYA■ chytrids may give us a good picture of what the ancestors of all fungi were like reproduction■ both sexual and asexual■ some have alternation of generations D.2. Phylum Zygomycota – zygomycetes apparently paraphyletic hyphae lack septa, except in reproductive structures hyphae typically multinucleate no dikaryotic hyphae: plasmogamy and karyogamy together, followed by zygosporangium formation, then followed by meiosis when conditions are right 5 of 12BIOL 1030 – TOPIC 3 LECTURE NOTES sexual reproduction: meiospores made in zygosporangia■ specialized, thick-coated microscopic structures that protect the diploid (zygotic) cells inside■ contain one or more zygotic cells■ considered “resting structures” because they are essentially dormant until an environmental signal of some sort sparks the zygotic cells to undergo meiosis, forming meiospores and breaking open the zygosporangium asexual reproduction■ more commonly seen than sexual reproduction for this group■ mitospore-forming sporangia on sporangiophore stalks ~1000 species known importance: includes many bread moldsD.3. Phylum Glomeromycota – glomeromycetes monophyletic newly defined, previously thought to be zygomycetes ~160 known species important for mycorrhizal relationships with many plants mycorrhizae: association of fungus with plant root■ a type of mutualism (relationship between 2 species where both benefit)■ fungus extends into soil and aids in uptake of nutrients (P, Zn, Cu in particular) for plant■ fungus obtains sugars from plant■ very common, found with most plant roots – ~90% of plants have a mycorrhizal relationship with