2These honey mushrooms are part of the visible portion of the largest organism on Earth. A single honey mushroom colony in Oregon covers and area of 8.9 sq. km (2200 acres).Figure: 20-COTitle:The Diversity of FungiCaption:
3Chapter 22 Outline 22.1 What Are the Key Features of Fungi? p. 424 22.2 What Are the Major Groups of Fungi? p. 42522.3 How Do Fungi Interact with Other Species? p. 43022.4 How Do Fungi Affect Humans? p. 433
4Section 22.1 Outline 22.1 What Are the Key Features of Fungi? Fungal Bodies Consist of Slender ThreadsFungi Obtain Their Nutrients from Other OrganismsFungi Propagate by SporesMost Fungi Can Reproduce Both Sexually and Asexually
5Fungal Body Structure Most fungi are multicellular Cells are surrounded by cell walls composed of chitin, a nitrogen-containing polysaccharideBody of almost all fungi is a mycelium, an interwoven mass of threadlike filaments called hyphae (singular, hypha)
6FIGURE 22-1 (part 1) The filamentous body of a fungus (a) A fungal mycelium spreads over decaying vegetation. The mycelium is composed of (b) a tangle of microscopic hyphae, only one cell thick, portrayed in cross section (c) to show their internal organization.
7Fungal Body StructureHyphae of most species are divided into many cells by partitions called septa (singular, septum); each cell possesses one or more nucleiPores in the septa allow cytoplasm to stream from one cell to the nextHyphae of some fungi lack septa, consisting of single elongated cells with hundreds or thousands of nucleiThe nuclei of most species are haploid
8FIGURE 22-1 (part 2) The filamentous body of a fungus The mycelium is composed of (b) a tangle of microscopic hyphae, only one cell thick, portrayed in cross section (c) to show their internal organization.
9Nutrition and Fungal Lifestyles All are heterotrophicSecrete enzymes outside their bodies and absorb the digested nutrientsHave diverse lifestylesFungal decomposers (saprobes) feed on dead organic material and wastesFungal parasites absorb nutrients from cells of living hosts and may cause diseaseSome symbiotic fungi live in mutually beneficial relationships with other organismsFungal predators consume living organisms
10Propagate by SporesSpores are haploid reproductive cells capable of developing into an adult fungusUsually produced in large numbersDispersed by animals or air currentsBoth asexual and sexual reproduction involve the production of spores within fruiting bodies
11FIGURE 22-2 Some fungi can eject spores A ripe earthstar mushroom, struck by a drop of water, releases a cloud of spores from the fruiting body that will be dispersed by air currents.
12Asexual Reproduction Typically occurs under stable conditions Can occur either by:Fragmentation of the myceliumAsexual spore formationHaploid mycelium produces haploid asexual spores by mitosisSpores germinate and develop into a new mycelium by mitosisResults in the rapid production of genetically identical clones
13Sexual ReproductionTypically occurs under conditions of environmental change or stressNeighboring haploid mycelia of different, but compatible mating types come into contact with each otherThe two different hyphae fuse so that the nuclei share a common cellThe different haploid nuclei fuse to form a diploid zygoteZygote undergoes meiosis to form haploid sexual spores
14Sexual ReproductionSpores germinate and develop into a new mycelium by mitosisResults in the production of genetically diverse fungal bodies
15Section 22.2 Outline 22.2 What Are the Major Groups of Fungi? Chytrids Produce Swimming SporesZygomycetes Can Reproduce by Forming Diploid SporesAscomycetes Form Spores in a Saclike CaseBasidiomycetes Produce Club-Shaped Reproductive StructuresSome Fungi Form Symbiotic Relationships
16Classification of Fungi Fungi have been assigned to four phyla based upon the way they produce sexual sporesChytridiomycota (chytrids)Zygomycota (zygote fungi)Ascomycota (sac fungi)Basidiomycota (club fungi)
17FIGURE 22-3 Evolutionary tree of the major groups of fungi
19The Chytrids The Chytrids Most are aquatic Reproduce both asexually and sexuallyForm flagellated spores that require water for dispersalFigure 22-4, p. 426, illustrates the chytrid fungus Allomyces in the midst of sexual reproduction
20FIGURE 22-4 Chytrid filaments These filaments of the chytrid fungus Allomyces are in the midst of sexual reproduction. The orange structures visible on many of the filaments will release male gametes; the clear structures will release female gametes. Chytrid gametes are flagellated, and these swimming reproductive structures aid dispersal of members of this mostly aquatic phylum
21The Chytrids Most feed on dead aquatic material Some species are parasites of plants and animalsOne chytrid species is a frog pathogen believed to be a major cause of the current worldwide die-off of frogsAccording to evolutionists, primitive chytrids are believed to have given rise to the other groups of modern fungi
22Zygomycetes Most live in soil or on decaying plant or animal material Reproduce both asexually and sexuallySexual spores are thick-walled zygosporesDuring asexual reproduction:Haploid spores are produced via mitosis in black spore cases called sporangiaSpores disperse and germinate to form new haploid hyphaeFigure 20-5, p. 427, depicts the asexual reproduction in Rhizopus, black bread mold
23The life cycle of a zygomycete FIGURE 22-5The life cycle of a zygomyceteTop: in asexual reproduction in the black bread mold (genus Rhizopus), haploid spores, produced within sporangia, disperse and germinate on food such as bread. Bottom: During sexual reproduction, hyphae of different mating types (designated + and - on the bread) contact one another and fuse, producing a diploid zygospore. The zygospore undergoes meiosis and germinates, producing sporangia that liberate haploid spores.
24AscomycetesLive in a variety of marine, freshwater, and terrestrial habitatsEach fruiting body contains numerous saclike cases called asci (singular, ascus)Reproduce both asexually and sexuallySexual spores form in saclike asci
25FIGURE 22-7a Diverse ascomycetes The cup-shaped fruiting body of the scarlet cup fungus (top)The morel (bottom), an edible delicacy. (Consult an expert before sampling any wild fungus – some are deadly!). (Consult an expert before sampling any wild fungusｴsome are deadly!)
26FIGURE 22-6 The life cycle of a typical ascomycete Top: In ascomycete asexual reproduction, haploid hyphae give rise to stalked structures that produce haploid spores. Bottom: In sexual reproduction, haploid nuclei of different mating types fuse to form diploid zygotes that divide and give rise to haploid ascospores.
27Ascomycetes Better known examples include Most of the food-spoiling moldsMorels and truffles (edible delicacies)Penicillium, the mold that produces penicillin (the first antibiotic)Yeasts (single-celled fungi)
28BasidiomycetesLive in a variety of marine, freshwater, and terrestrial habitatsEach fruiting body contains numerous club-shaped structures called basidia (singular, basidium)Usually reproduce sexuallySexual spores form in club-shaped basidiaFigure 22-9, p. 429, depicts an overview of sexual reproduction in a basidiomycetes
29FIGURE 22-8 The life cycle of a typical basidiomyce
30Diverse basidiomycetes FIGURE 22-9bDiverse basidiomycetes(b) Shelf fungi, some the size of dessert plates, are conspicuous on trees.FFIGURE 22-9aDiverse basidiomycetes(a) The giant puffball Lycopedon giganteum may produce up to 5 trillion spores.
31FIGURE 22-9c Diverse basidiomycetes (c) The spores of stinkhorns are carried on the outside of a slimy cap that smells terrible to humans, but appeals to flies. The flies lay their eggs on the stinkhorn, and inadvertently disperse the spores that stick to their bodies.
32Basidiomycetes Better known examples include Mushrooms (some are edible, others are poisonous)PuffballsShelf fungi (decomposers of wood)StinkhornsRusts and smuts (plant parasites)Yeasts
33Fairy Rings A fairy ring is a circular pattern of mushroom growth Fairy rings form at the leading edge of an expanding underground fungal myceliumThe wider the diameter of the ring, the older the myceliumSome fairy rings are estimated to be 700 years old
34FIGURE 22-10 A mushroom fairy ring Mushrooms emerge in a fairy ring from an underground fungal mycelium, growing outward from a central point where a single spore germinated, perhaps centuries ago.
35Section 22.3 Outline 22.3 How Do Fungi Interact with Other Species? Lichens Are Formed by Fungi That Live with Photosynthetic Algae or BacteriaMycorrhizae Are Fungi Associated with Plant RootsEndophytes Are Fungi That Live Inside Plant Stems and LeavesSome Fungi Are Important Recyclers
36Symbiotic Relationships A symbiosis is a close interaction between organisms of different species over an extended period of timeThe fungal member of a symbiotic relationship may be harmful (a parasite of plants or animals) or beneficial (lichens and mycorrhizae)
37LichensLichens are symbiotic associations between fungi (usually an ascomycete) and algae or cyanobacteriaFungus provides photosynthetic partner with shelter and protectionPhotosynthetic partner provides fungus with food (sugar)
38FIG 22-11 The lichen: A symbiotic partnership Most lichens have a layered structure bounded on the top and bottom by an outer layer formed from fungal hyphae. The fungal hyphae emerge from the lower layer, forming attachments that anchor the lichen to a surface, such as a rock or a tree. An algal layer in which the alga and fungus grow in close association lies beneath the upper layer of hyphae.
39LichensGrow 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
40FIG 22-12a Diverse lichens(a) A colorful encrusting lichen, growing on dry rock, illustrates the tough independence of this symbiotic combination of fungus and algae.(b) A leafy lichen grows from a dead tree branch.
41MycorrhizaeMycorrhizae (singular, mycorrhiza) are symbiotic associations between fungi and plant rootsFungus provides plant with water, minerals, and organic nutrients it absorbs from the soilPlant provides fungus with food (sugar)80% of plants with roots have mycorrhizaeRelationship may have helped plants colonize land
42FIGURE 22-13 Mycorrhizae enhance plant growth Hyphae of mycorrhizae entwining about the root of an aspen tree. Plants grow significantly better in a symbiotic association with these fungi, which help make nutrients and water available to the roots.
43EndophytesEndophytes are fungi that live inside the above-ground tissues of plantsSome are parasites that cause plant diseasesSome are beneficial to host plantsSome ascomycete species live inside grasses and produce substances that are distasteful or toxic to insects and grazing mammals, protecting the grasses from predation
44RecyclersFungi are Earth’s undertakers, feeding on the dead of all kingdomsFungal 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
45Section 22.4 Outline 22.4 How Do Fungi Affect Humans? Fungi Attack Plants That Are Important to PeopleFungi Cause Human DiseasesFungi Can Produce ToxinsMany Antibiotics Are Derived from FungiFungi Make Important Contributions to GastronomyFungal Ingenuity
46Fungi Attack PlantsFungal parasites cause the majority of plant diseasesAscomycete parasites cause Dutch elm disease and Chestnut blightRusts and smuts are basidiomycete parasites that cause considerable damage to grain crops
47FIGURE Corn smutThis basidiomycete pathogen destroys millions of dollars' worth of corn each year. Even a pest like corn smut has its admirers, though. In Mexico this fungus is known as huitlacoche and is considered to be a great delicacy.
48Fungi Attack PlantsFungi can destroy plant material that has been harvested for human useCause wooden structures to rotDamage cotton and wool fabrics
49Fungi Attack Plants Some fungi benefit agriculture Used to control insect pests such as rice weevils, tent caterpillars, aphids, citrus mites, and grasshoppersFungi identified that attack mosquitoes that transmit malaria
50FIGURE 22-15a Helpful fungal parasites Fungal pathogens can be helpful to humans. For example, fungi such as (a) the Cordyceps species that has killed this grasshopper are used by farmers to control insect pests.
51FIGURE 22-15b Helpful fungal parasites (b) Some fungi might one day be used to help protect humans from disease. A malaria-carrying mosquito infected by Beauveria species is transformed from a healthy animal (top) to a fungus-encrusted corpse in less than two weeks.
52Fungi Cause Human Diseases Athlete’s foot, jock itch, and ringworm are caused by fungi that attack the skinValley fever and histoplasmosis are caused by fungi that attack the lungsInfection occurs when victim inhales spores
53Fungi Cause Human Diseases Most vaginal infections are caused by the yeast Candida albicans
54FIGURE 22-16 The unusual yeast Yeasts are unusual, normally non-filamentous ascomycetes that reproduce most commonly by budding. The yeast shown here is Candida, a common cause of vaginal infections.
55Fungi Produce ToxinsMolds of the genus Aspergillus produce aflatoxins, highly toxic, carcinogenic compoundsInfect foods such as peanuts
56Fungi Produce ToxinsClaviceps purpurea (an ascomycete) produces several toxinsInfects rye plants and causes ergot diseaseSymptoms of ergot poisoning include vasoconstriction of blood vessels, vomiting, convulsive twitching, hallucinations, and death
57Fungi Produce Antibiotics PenicillinFirst antibiotic to be discoveredUsed to combat bacterial diseases
58FIGURE PenicilliumPenicillium growing on an orange. Reproductive structures, which coat the fruit's surface, are visible, while hyphae beneath draw nourishment from inside. The antibiotic penicillin was first isolated from this fungus.
59Fungi Produce Other Drugs CyclosporinUsed to suppress the immune response during organ transplants
60Fungi Contribute to Gastronomy Certain ascomycete molds impart flavor to some of the world’s most famous cheesesRoquefortCamembertStiltonGorgonzola
61Fungi Contribute to Gastronomy Yeasts are used in the production of wine, beer, and breadWine is produced when yeasts ferment fruit sugars; ethyl alcohol is retained, while CO2 is released
62Fungi Contribute to Gastronomy Beer is derived when yeasts ferment sugars in germinating grains (usually barley); ethyl alcohol and CO2 are retainedBread rises when yeasts ferment sugar that has been added to bread dough; both ethyl alcohol and CO2 escape during baking
63Fungi Contribute to Gastronomy Some fungi are consumed directlyMushrooms (a basidiomycete)Morels (an ascomycete)Truffles (an ascomycete)
64FIGURE The truffleTruffles, rare ascomycetes (each about the size of a small apple), are a gastronomic delicacy.
65Fungal IngenuityThe truffle has evolved an effective adaptation for dispersal of its sporesReleases an odor which causes pigs and other animals to dig it up, scattering spores to the windsThe zygomycete Pilobolus has evolved bulb tops that blast off, spreading spores
66FIGURE 22-19 An explosive zygomycete The delicate, translucent reproductive structures of the zygomycete Pilobolus literally blow their tops when ripe, dispersing the black caps with their payload of spores.
67Fungal IngenuityArthrobotrys cleverly traps and “strangles” microscopic roundworms called nematodes to obtain nutrients
68FIGURE 22-20 Nemesis of nematodes Arthrobotrys, the nematode (roundworm) strangler, traps its prey in a noose-like modified hypha that swells when the inside of the loop is contacted.