Fungi APBio

Slide 1: Chapter 22 The Fungi

Slide 2: Chapter 22 Fungal Anatomy Multicellular Body of almost all fungi is a mycelium, an interwoven mass of threadlike filaments called hyphae (singular, hypha) Chitin cell walls Hyphae of most species are divided into many cells by partitions called septa (singular, septum); each cell possesses one or more nuclei • Pores in the septa allow cytoplasm to stream from one cell to the next

Slide 3: The Filamentous Body Chapter 22 of a Fungus (a) Mycelium (c) Hyphal Cells (cutaway) Haploid Cytoplasm Nuclei Septum (b) Individual Hyphae Pore Cell Walls

Slide 4: Chapter 22 Chytrid Filaments Male Female

Slide 5: Chapter 22 Fungal Nutrition Three major types of heterotrophic nutrition • Saprophytic—digestion of dead organisms • Parasitic—digestion of live organisms • Symbiotic—mutual benefit of two independent organisms

Slide 6: Chapter 22 Fungal Reproduction Asexual • Fragmentation • Asexual spore formation – Haploid mycelium produces haploid asexual spores by mitosis – Spores germinate and develop into a new mycelium by mitosis Results in the rapid production of genetically identical clones

Slide 7: Chapter 22

Slide 8: Chapter 22 Fungal Sexual Reproduction Typically occurs under conditions of environmental change or stress • Neighboring haploid mycelia of different, but compatible mating types come into contact with each other • The two different hyphae fuse so that the nuclei share a common cell • The different haploid nuclei fuse to form a diploid zygote • Zygote undergoes meiosis to form haploid sexual spores

Slide 9: Zygomycete Life Cycle (a) Chapter 22 Sporangia Spores (haploid) Diploid 2n Zygospore Haploid germinates 1n Hyphae of opposite mating types fuse to (b) Photo of Sporangia form zygospore.

Slide 10: Zygomycete Life Cycle (b) Chapter 22 Hyphae of opposite mating types (+ & -) fuse. Zygospore germinates MEIOSIS NUCLEI FUSE Haploid 1n Diploid Zygospore Diploid formed 2n

Slide 11: Chapter 22 Classification of Fungi Fungi have been assigned to four phyla based upon the way they produce sexual spores • Chytridiomycota (chytrids) • Zygomycota (zygote fungi) • Ascomycota (sac fungi) • Basidiomycota (club fungi)

Slide 13: Chapter 22 The Chytrids Chytrids • Most are aquatic • Reproduce both asexually and sexually • Form flagellated spores that require water for dispersal • Figure 22-4, p. 426, illustrates the chytrid fungus Allomyces in the midst of sexual reproduction

Slide 15: Chapter 22 The Chytrids Most feed on dead aquatic material Some species are parasites of plants and animals • One chytrid species is a frog pathogen believed to be a major cause of the current worldwide die-off of frogs Primitive chytrids are believed to have given rise to the other groups of modern fungi

Slide 16: Chapter 22 Zygomycetes Most live in soil or on decaying plant or animal material Reproduce both asexually and sexually • Sexual spores are thick-walled zygospores During asexual reproduction: • Haploid spores are produced via mitosis in black spore cases called sporangia • Spores disperse and germinate to form new haploid hyphae

Slide 17: Chapter 22 Zygomycetes During sexual reproduction • Two hyphae of different mating types come into contact and fuse • Nuclei fuse to form a diploid zygospore, a tough, resistant structure that can remain dormant for long periods until conditions are favorable • Meiosis occurs as the zygospore germinates • Resulting spores disperse and germinate to form new haploid hyphae that can enter either the asexual or sexual cycle

Slide 21: Chapter 22 Ascomycetes Live in a variety of marine, freshwater, and terrestrial habitats Reproduce both asexually and sexually • Sexual spores form in saclike asci During asexual reproduction • Haploid spores are produced via mitosis at the tips of specialized hyphae • Spores disperse and germinate to form new haploid hyphae

Slide 22: Chapter 22 Ascomycetes During sexual reproduction • Two hyphae of different mating types come into contact and fuse, resulting in the formation of a fruiting body

Slide 24: Chapter 22 Ascomycetes Better known examples include • Most of the food-spoiling molds • Morels and truffles (edible delicacies) • Penicillium, the mold that produces penicillin (the first antibiotic) • Yeasts (single-celled fungi)

Slide 25: Chapter 22 Some Ascomycetes (a) Scarlet Cup Fungus (b) Morel

Slide 26: Chapter 22 Basidiomycetes Live in a variety of marine, freshwater, and terrestrial habitats Usually reproduce sexually • Sexual spores form in club-shaped basidia During sexual reproduction: • Two hyphae of different mating types come into contact and fuse, resulting in the formation of a fruiting body

Slide 27: Chapter 22 Basidiomycete Life Cycle Haploid Nuclei Fusion forms diploid zygote. Basidia SIS on gills MEIO Basidiospores (haploid) Diploid Mushroom gills 2n bear reproductive Haploid basidia. 1n

Slide 28: Chapter 22 Basidiomycete Life Cycle Basidiospores (haploid) Basidia on gills Hyphae aggregate to form mushroom “+” Mating Strain “-” Mating Strain Basidiospores germinate forming hyphae (haploid). + Diploid - Hyphae fuse, but 2n haploid nuclei Haploid remain separate 1n in binucleate cells

Slide 29: Chapter 22 Basidiomycetes Better known examples include • Mushrooms (some are edible, others are poisonous) • Puffballs • Shelf fungi (decomposers of wood) • Stinkhorns • Rusts and smuts (plant parasites) • Yeasts

Slide 30: Chapter 22 Some Basidiomycetes (a) Giant Puffball (b) Shelf Fungi

Slide 31: Chapter 22 Fairy Rings A fairy ring is a circular pattern of mushroom growth Fairy rings form at the leading edge of an expanding underground fungal mycelium • The wider the diameter of the ring, the older the mycelium • Some fairy rings are estimated to be 700 years old

Slide 32: Chapter 22 A Mushroom Fairy Ring

Slide 33: Chapter 22 Symbiotic Relationships A symbiosis is a close interaction between organisms of different species over an extended period of time The fungal member of a symbiotic relationship may be harmful (a parasite of plants or animals) or beneficial (lichens and mycorrhizae)

Slide 34: Chapter 22 Lichens Lichens are symbiotic associations between fungi (usually an ascomycete) and algae or cyanobacteria • Fungus provides photosynthetic partner with shelter and protection • Photosynthetic partner provides fungus with food (sugar)

Slide 35: Lichens: Chapter 22 Symbiotic Partnerships Algal Layer Fungal Hyphae Attachment Structure

Slide 36: Chapter 22 Lichens Grow on a wide variety of materials (soils, tree trunks and branches, rocks, fences, roofs, and walls) Are able to survive environmental extremes (newly formed volcanic islands, deserts) Are very diverse in form

Slide 37: Chapter 22 Lichens Covering a Rock

Slide 38: Chapter 22 Mycorrhizae Mycorrhizae (singular, mycorrhiza) are symbiotic associations between fungi and plant roots • Fungus provides plant with water, minerals, and organic nutrients it absorbs from the soil • Plant provides fungus with food (sugar) 80% of plants with roots have mycorrhizae Relationship may have helped plants colonize land

Slide 39: Mycorrhizae Chapter 22 Enhance Plant Growth Mycorrhizae

Slide 40: Chapter 22 Recyclers Fungi are Earth’s undertakers, feeding on the dead of all kingdoms Fungal saprophytes (feeding on dead organisms) release extracellular substances that digest the tissues of the dead and liberate carbon, nitrogen, phosphorus compounds, and minerals that can be reused by plants

Slide 41: Chapter 22 Fungi Attack Plants Fungal parasites cause the majority of plant diseases • Ascomycete parasites cause Dutch elm disease and Chestnut blight • Rusts and smuts are basidiomycete parasites that cause considerable damage to grain crops

Slide 42: Chapter 22 Corn Smut

Slide 43: Chapter 22 Fungi Cause Human Diseases Athlete’s foot, jock itch, and ringworm are caused by fungi that attack the skin Valley fever and histoplasmosis are caused by fungi that attack the lungs • Infection occurs when victim inhales spores Most vaginal infections are caused by the yeast Candida albicans

Slide 44: Chapter 22 Yeasts Candida sp.

Slide 45: Chapter 22 Fungi Produce Toxins Claviceps purpurea (an ascomycete) produces several toxins • Infects rye plants and causes ergot disease • Symptoms of ergot poisoning include vasoconstriction of blood vessels, vomiting, convulsive twitching, hallucinations, and death Penicillin • First antibiotic to be discovered • Used to combat bacterial diseases

Slide 46: Chapter 22 Penicillium

Slide 47: Chapter 22 Fungi Contribute to Gastronomy Certain ascomycete molds impart flavor to some of the world’s most famous cheeses • Roquefort • Camembert • Stilton • Gorgonzola Yeasts are used in the production of wine, beer, and bread Wine is produced when yeasts ferment fruit sugars; ethyl alcohol is retained, while CO2 is released

Slide 48: Chapter 22 Fungi Contribute to Gastronomy Beer is derived when yeasts ferment sugars in germinating grains (usually barley); ethyl alcohol and CO2 are retained Bread rises when yeasts ferment sugar that has been added to bread dough; both ethyl alcohol and CO2 escape during baking Some fungi are consumed directly • Mushrooms (a basidiomycete) • Morels (an ascomycete) • Truffles (an ascomycete)

Slide 49: Chapter 22 Truffles

Slide 50: Chapter 22 Fungal Ingenuity The truffle has evolved an effective adaptation for dispersal of its spores • Releases an odor which causes pigs and other animals to dig it up, scattering spores to the winds The zygomycete Pilobolus has evolved bulb tops that blast off, spreading spores

Slide 51: Pilobolus: Chapter 22 An Explosive Zygomycete

Slide 52: Chapter 22 Fungal Ingenuity Arthrobotrys cleverly traps and “strangles” microscopic roundworms called nematodes to obtain nutrients

Slide 53: Chapter 22 The Nemesis of Nematodes Unfortunate nematode Special hypha with noose

Slide 54: Chapter 22 The End

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