Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Chapter 22 The Diversity of Fungi Lecture Outlines by Gregory Ahearn, University of North Florida Copyright © 2011 Pearson Education Inc. What Are the Key Features of Fungi? What Are the Major Groups of Fungi? How Do Fungi Interact with Other Species? How Do Fungi Affect Humans? What do Bob Dylan, the Salem Witch Trials, and Athlete’s Foot have in common? Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 22.1 What Are the Key Features of Fungi? Fungal bodies consist of slender threads – Most fungi are multicellular – Cells are surrounded by cell walls composed of chitin, a nitrogen-containing polysaccharide – The body of almost all fungi is a mycelium, an interwoven mass of threadlike filaments called hyphae (singular, hypha) Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 22.1 What Are the Key Features of Fungi? Fungal bodies consist of slender threads (continued) – 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 –Fungi cannot move, but grow rapidly in any direction within a suitable environment Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. Author Animation: The Structure of Fungi Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. The Filamentous Body of a Fungus cell wall cytoplasm pore septum hyphae (a) Mycelium (b) Hyphae (c) Hypha cross-section Fig. 22-1 Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 22.1 What Are the Key Features of Fungi? Fungi obtain their nutrients from other organisms – Fungi secrete enzymes outside their bodies and absorb the digested nutrients – Fungal decomposers feed on dead organic material and wastes – Fungal parasites absorb nutrients from cells of living hosts and may cause disease – Some symbiotic fungi live in mutually beneficial relationships with other organisms – Fungal predators consume living organisms Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. Nemesis of Nematodes Fig. 22-2 Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 22.1 What Are the Key Features of Fungi? Fungi propagate by spores – Spores are tiny reproductive packages capable of developing into adult fungi –They are often produced in large numbers, and are dispersed by animals or air currents Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. Some Fungi Can Eject Spores Fig. 22-3 Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 22.1 What Are the Key Features of Fungi? Most fungi can reproduce both asexually and sexually – During asexual reproduction: –For the most part, asexual reproduction occurs under stable conditions –A haploid mycelium produces haploid asexual spores by mitosis –Spores germinate and develop into a new mycelium by mitosis –This results in the rapid production of genetically identical clones Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 22.1 What Are the Key Features of Fungi? During sexual reproduction: – 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 – The zygote undergoes meiosis to form haploid sexual spores – The spores germinate and develop into a new mycelium by mitosis – This results in the production of fungal bodies that are genetically distinct from either parent Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 22.2 What Are the Major Groups of Fungi? Fungus species are classified into five phyla – Chytridiomycota (chytrids) – Zygomycota (zygomycetes) – Glomeromycota (glomeromycetes) – Basidiomycota (basidiomycetes) – Ascomycota (ascomycetes) Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. Evolutionary Tree of the Major Groups of Fungi Fig. 22-4 Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. Table 22-1 Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 22.2 What Are the Major Groups of Fungi? The chytrids – Most chytrids are aquatic –They are distinguished from other fungi by forming flagellated spores that require water for dispersal –They reproduce both asexually and sexually Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. Chytrid Filaments flagellum eyespot contractile vacuole stored food nucleus nucleolus chloroplasts Fig. 22-5 Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 22.2 What Are the Major Groups of Fungi? The chytrids (continued) – 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 Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 22.2 What Are the Major Groups of Fungi? The zygomycetes – Most zygomycetes live in soil or on decaying plant or animal material –The group includes the black bread mold Rhizopus –They reproduce both asexually and sexually Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 22.2 What Are the Major Groups of Fungi? The zygomycetes (continued) – During asexual reproduction: –Haploid spores are produced in black spore cases called sporangia –The spores disperse through the air and germinate to form new haploid hyphae Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 22.2 What Are the Major Groups of Fungi? The zygomycetes (continued) – During sexual reproduction: – Two hyphae of different mating types come into contact and fuse to form a zygosporangium that contains multiple haploid nuclei – Haploid nuclei fuse within the zygosporangium to form diploid nuclei – Diploid nuclei give rise to stalked sporangia that produce haploid spores that disperse, germinate, and develop into new haploid hyphae Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. Author Animation: The Life Cycle of a Zygomycete Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. The Life Cycle of a Zygomycete 1 In asexual reproduction, mycelia give rise to sporangia that produce haploid spores sporangia spores hypha 7 If spores formed by sexual or asexual reproduction land on a suitable substrate, they develop into hyphae ASEXUAL REPRODUCTION hypha, (–) mating type sporangia hypha, (+) mating type hypha spores sporangia 6 Haploid spores disperse from the sporangia 2 Sexual reproduction begins when hyphae of opposite mating types meet SEXUAL REPRODUCTION 3 The two hyphae fuse, forming a zygosporangium that contains haploid nuclei from the two parents 5 The diploid nuclei in the zygosporangium undergo meiosis and give rise to stalked sporangia FUSION OF NUCLEI 4 The haploid nuclei in the zygosporangium fuse to form diploid nuclei MEIOSIS haploid (n) zygosporangium diploid (2n) Fig. 22-6 Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 22.2 What Are the Major Groups of Fungi? The glomeromycetes – Glomeromycetes live in intimate contact with the roots of plants – Their hyphae penetrate root cells and form microscopic branching structures inside the cell – The interaction forms a beneficial relationship called a mycorrhiza Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. Glomeromycete in a Plant Cell Fig. 22-7 Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 22.2 What Are the Major Groups of Fungi? The glomeromycetes (continued) – Reproduction in the glomeromycetes: –Sexual reproduction has not been observed –During asexual reproduction, clusters of spores are produced by mitosis and remain outside the host plant cell at the tips of hyphae –When the spores germinate, hyphae grow into the surrounding soil and penetrate new plant roots Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 22.2 What Are the Major Groups of Fungi? The basidiomycetes – The basidiomycetes are called the club fungi because they produce club-shaped reproductive structures – These fungi typically reproduce sexually – During reproduction, two hyphae of different mating types come into contact and fuse, resulting in the formation of a fruiting body – Each fruiting body contains numerous club-shaped structures called basidia (singular, basidium) – Nuclei within each basidium fuse, forming a diploid nucleus Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 22.2 What Are the Major Groups of Fungi? The basidiomycetes (continued) –The diploid nucleus divides by meiosis producing four haploid basidiospores –Basidiomycete fruiting bodies are the familiar mushrooms, puffballs, shelf fungi, and stinkhorns –Basidiospores are released from the fruiting bodies, and disperse and germinate to form new haploid hyphae that enter the sexual cycle Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. Author Animation: The Life Cycle of a Basidiomycete Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. The Life Cycle of a Typical Basidiomycete 2 The fused hyphae grow into a mycelium in which each cell contains a haploid nucleus from each parent 1 Sexual reproduction begins when hyphae of opposite mating types meet and fuse hypha, (–) mating type hypha, (+) mating type 3 Hyphae from the mycelium aggregate to form a mushroom 7 After dispersal, the basidiospores germinate and develop into hyphae 6 The diploid nuclei divide by meiosis and give rise to haploid basidiospores that are ejected 4 Reproductive cells called basidia form on the mushroom's gills 5 The two haploid nuclei in each basidium fuse to form a diploid nucleus MEIOSIS FUSION OF NUCLEI haploid (n) diploid (2n) Fig. 22-8 Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. Diverse Basidiomycetes Fig. 22-9 Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. A Mushroom Fairy Ring Fig. 22-10 Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 22.2 What Are the Major Groups of Fungi? The ascomycetes – The ascomycetes are called sac fungi and reproduce both asexually and sexually – During asexual reproduction: –Haploid spores are produced at the tips of specialized hyphae –Spores disperse and germinate to form new haploid hyphae Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 22.2 What Are the Major Groups of Fungi? The ascomycetes (continued) – During sexual reproduction: –Two hyphae of different mating types come into contact and fuse, resulting in the formation of a fruiting body –At the tips of some hyphae in the fruiting body, a saclike case called an ascus (plural, asci) forms –Nuclei within each ascus fuse, producing a diploid nucleus Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 22.2 What Are the Major Groups of Fungi? Sexual reproduction (continued) –The diploid nucleus divides by meiosis followed by mitosis to produce eight ascospores (haploid sexual spores) –Ascospores disperse and germinate to form new haploid hyphae that can enter either the asexual or sexual cycle Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. The Life Cycle of a Typical Ascomycete 1 In asexual reproduction, haploid spores develop at the tips of hyphae, disperse, and germinate to form new hyphae 2 Sexual reproduction begins when hyphae of opposite mating types meet and form connected reproductive fruiting body spores ASEXUAL REPRODUCTION 3 Haploid nuclei move from the (–) to the (+) structure hypha, (–) mating type hypha, (+) mating type hyphae 9 The ascus bursts, dispersing spores that germinate and grow into hyphae ascus 4 The structures containing the pooled (+) and (–) nuclei develop into hyphae that are incorporated into a fruiting body SEXUAL REPRODUCTION 5 The tips of some hyphae in the fruiting body form asci that contain two haploid nuclei FUSION OF NUCLEI 8 The haploid nuclei divide by mitosis and give rise to eight ascospores 7 The diploid nucleus divides by meiosis to produce four haploid nuclei 6 The haploid nuclei in an ascus fuse to form a diploid nucleus MEIOSIS haploid (n) diploid (2n) Biology: Life on Earth, 9e Fig. 22-11 Copyright © 2011 Pearson Education Inc. 22.2 What Are the Major Groups of Fungi? The ascomycetes (continued) – Better known examples include: –Most food-spoiling molds –Morels and truffles (edible delicacies) –Penicillium, the mold that produces penicillin (the first antibiotic) –Yeasts (unicellular fungi) Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. Diverse Ascomycetes Fig. 22-12 Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 22.3 How Do Fungi Interact with Other Species? Symbiotic relationships – A symbiotic relationship 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 or beneficial Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 22.3 How Do Fungi Interact with Other Species? Lichens are formed by fungi that live with photosynthetic algae or bacteria – The fungus provides its photosynthetic partner with shelter and protection – The photosynthetic partner in turn provides the fungus with food (sugar) Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 22.3 How Do Fungi Interact with Other Species? Lichens are formed by fungi that live with photosynthetic algae or bacteria (continued) – Lichens grow on a wide variety of materials (soils, tree trunks and branches, rocks, fences, roofs, and walls) – They are able to survive environmental extremes (newly formed volcanic islands, deserts) – They are very diverse in form Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. Diverse Lichens Fig. 22-14 Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 22.3 How Do Fungi Interact with Other Species? Mycorrhizae (singular, mycorrhiza) are symbiotic associations between fungi and plant roots – The fungi digest and absorb minerals and organic nutrients from the soil, passing some of them directly into the plant root cells – The plant provides the fungi with energy-rich sugar molecules produced photosynthetically by the plant – Plants without mycorrhizal fungi tend to be smaller and less vigorous than are plants with mycorrhizal partners Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. Micorrhizae Enhance Plant Growth Fig. 22-15 Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 22.3 How Do Fungi Interact with Other Species? Mycorrhizae may have helped plants invade land – The relationship between an aquatic fungus and a green alga could have helped the alga acquire the water and mineral nutrients it needed to survive out of water – Fossils formed just after the invasion to land show that fully developed mycorrhizae were present very early in the evolution of land plants – This suggests that a simpler plant-fungus association might have been present even earlier Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 22.3 How Do Fungi Interact with Other Species? Endophytes are fungi that live inside plant stems and leaves – Some are parasites that cause plant diseases – Some are beneficial to the host plant –Some ascomycete species live inside grasses and produce substances that are distasteful or toxic to insects and grazing mammals, protecting the grasses from predation Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 22.3 How Do Fungi Interact with Other Species? Some fungi are important decomposers – Fungi are Earth’s undertakers, feeding on the dead of all kingdoms – Fungal saprophytes (which feed on dead organisms) release extracellular substances that digest the tissues of the dead and liberate carbon, nitrogen, and phosphorus compounds, as well as minerals that can be reused by plants Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 22.4 How Do Fungi Affect Humans? Fungi attack plants that are important to people – 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 Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. Corn Smut Fig. 22-16 Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 22.4 How Do Fungi Affect Humans? Fungi attack plants that are important to people (continued) – Fungi can destroy plant material that has been harvested for human use –They cause wooden structures to rot –Some ascomycete molds secrete enzymes that damage cotton and wool fabrics Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 22.4 How Do Fungi Affect Humans? Fungi attack plants that are important to people (continued) – Some fungi benefit agriculture –Some fungal parasites are used to control insect pests such as termites, rice weevils, tent caterpillars, aphids, citrus mites, and other pests – Certain fungi attack mosquitoes, which transmit malaria Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. Helpful Fungal Parasites Fig. 22-17 Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 22.4 How Do Fungi Affect Humans? Fungi cause human diseases – Athlete’s foot, jock itch, and ringworm are caused by fungi that attack the skin – Most vaginal infections are caused by the yeast Candida albicans – Valley fever and histoplasmosis are caused by fungi that attack the lungs –Infection occurs when the victim inhales spores Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. The Unusual Yeast (Candida) Fig. 22-18 Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 22.4 How Do Fungi Affect Humans? Fungi can produce toxins – Molds of the genus Aspergillus produce aflatoxins that are highly toxic, carcinogenic compounds – They infect foods such as peanuts – Claviceps purpurea (an ascomycete) produces several toxins – It infects rye plants and causes a disease called ergot – Symptoms of ergot poisoning include vasoconstriction of blood vessels, vomiting, convulsive twitching, hallucinations, and death Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. The Salem witch hunts of 1692 may have initially been caused by an infestation of a microbiological poison. The fungus Claviceps purpurea, commonly known as rye smut, produces the poison ergot. http://www.history.com/videos/salem-witch-trials#salem-witchtrials Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 22.4 How Do Fungi Affect Humans? Many antibiotics are derived from fungi – Penicillin is produced by an ascomycete mold –It was the first antibiotic to be discovered and is used to combat bacterial diseases – Cyclosporin –Used to suppress the immune response after organ transplants Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. Penicillium Fig. 22-19 Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 22.4 How Do Fungi Affect Humans? Fungi make important contributions to gastronomy – Wild and cultivated basidomycete mushrooms, such as morels and truffles, are highly prized – Certain ascomycete molds impart flavor to some of the world’s most famous cheeses –Roquefort –Camembert –Stilton –Gorgonzola Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. The Truffle Fig. 22-20 Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 22.4 How Do Fungi Affect Humans? Fungi make important contributions to gastronomy (continued) – 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 Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 22.4 How Do Fungi Affect Humans? Fungi make important contributions to gastronomy (continued) – 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 Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc.