Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece Lectures by Chris Romero Chapter 31 Fungi

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Overview: Mighty Mushrooms Fungi are diverse and widespread They are essential for the well-being of most terrestrial ecosystems because they break down organic material and recycle vital nutrients

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Concept 31.1: Fungi are heterotrophs that feed by absorption Despite their diversity, f ungi share key traits, most importantly the way in which they derive nutrition

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Nutrition and Fungal Lifestyles Fungi are heterotrophs but do not ingest their food They secrete exoenzymes that break down complex molecules, and then they absorb the smaller compounds

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Fungi exhibit diverse lifestyles: – Decomposers – Parasites – Mutualistic symbionts

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Body Structure The morphology of multicellular fungi enhances their ability to absorb nutrients Fungi consist of mycelia, networks of branched hyphae adapted for absorption Most fungi have cell walls made of chitin Animation: Fungal Reproduction and Nutrition Animation: Fungal Reproduction and Nutrition

LE 31-2 Reproductive structure Hyphae Spore-producing structures Mycelium 20 µm

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Septate fungi have hyphae divided into cells by septa, with pores allowing cell-to-cell movement Coenocytic fungi lack septa Nuclei Septate hypha Septum Pore Cell wall Nuclei Coenocytic hypha

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Mycorrhizae are mutually beneficial relationships between fungi and plant roots – Ectomycorrhizal fungi form sheaths of hyphae over a root and also grow into the extracellular spaces of the root cortex – Endomycorrhizal fungi extend hyphae through the cell walls of root cells and into tubes formed by invagination of the root cell membrane

LE 31-4 Hyphae adapted for trapping and killing prey Fungal hypha Haustorium Plant cell Haustoria Plant cell plasma membrane Plant cell wall Nematode Hyphae 25 µm

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 31.2: Fungi produce spores through sexual or asexual life cycles Fungi propagate themselves by producing vast numbers of spores, either sexually or asexually

LE 31-5–3 Haploid (n) Key Heterokaryotic (unfused nuclei from different parents) Diploid (2n) PLASMOGAMY (fusion of cytoplasm) Heterokaryotic stage KARYOGAMY (fusion of nuclei) Mycelium SEXUAL REPRODUCTION Zygote Spores GERMINATION MEIOSIS Spore-producing structures ASEXUAL REPRODUCTION Spores GERMINATION Spore-producing structures

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Sexual Reproduction Plasomogamy is the union of two parent mycelia In many fungi, the haploid nuclei from each parent do not fuse right away; they coexist in the mycelium, called a heterokaryon In some fungi, the haploid nuclei pair off two to a cell; such a mycelium is said to be dikaryotic

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Asexual Reproduction In addition to sexual reproduction, many fungi can reproduce asexually Many of these species grow as mold, sometimes on fruit, bread, and other foods

LE µm

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 10 m Parent cell Bud Other fungi that can reproduce asexually are yeasts, which inhabit moist environments Instead of producing spores, yeasts reproduce asexually by simple cell division

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Many molds and yeasts have no known sexual stage Mycologists have traditionally called these deuteromycetes, or imperfect fungi

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 31.3: Fungi descended from an aquatic, single-celled, flagellated protist Systematists now recognize Fungi and Animalia as sister kingdoms In other words, fungi and animals are more closely related to each other than they are to plants or other eukaryotes

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Origin of Fungi Molecular evidence supports the hypothesis that fungi and animals diverged from a common unicellular, flagellated ancestor Fungi probably evolved before the colonization of land by multicellular organisms The oldest undisputed fossils of fungi are only about 460 million years old

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Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Move to Land Fungi were among the earliest colonizers of land, probably as symbionts with early land plants

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 31.4: Fungi have radiated into a diverse set of lineages Fungi phylogeny is the subject of much research Molecular analysis has helped clarify evolutionary relationships between fungal groups, although areas of uncertainty remain

LE 31-9 Chytrids Zygote fungi Arbuscular mycorrhizal fungi Sac fungi Club fungi Basidiomycota Ascomycota Glomeromycota Zygomycota Chytridiomycota

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Chytrids Chytrids (phylum Chytridiomycota) are found in freshwater and terrestrial habitats They can be saprobic or parasitic Molecular evidence supports the hypothesis that chytrids diverged earliest in fungal evolution Chytrids are unique among fungi in having flagellated spores, called zoospores

LE Hyphae 25 µm Flagellum 4 µm

LE Zygomycetes and other chytrids Some chytrids Glomeromycetes, ascomycetes, and basidiomycetes Common ancestor Key Loss of flagella

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Zygomycetes The zygomycetes (phylum Zygomycota) exhibit great diversity of life histories They include fast-growing molds, parasites, and commensal symbionts The zygomycetes are named for their sexually produced zygosporangia The life cycle of black bread mold (Rhizopus stolonifer) is fairly typical of the phylum

LE Rhizopus growing on bread Mating type (+) Mating type (–) Gametangia with haploid nuclei PLASMOGAMY Key Haploid (n) Heterokaryotic (n + n) Diploid (2n) 100 µm Young zygosporangium (heterokaryotic) SEXUAL REPRODUCTION KARYOGAMY Zygosporangium (heterokaryotic) Diploid nuclei MEIOSIS Sporangium Mycelium Dispersal and germination Dispersal and germination ASEXUAL REPRODUCTION Sporangia 50 µm

LE mm Pilobolus aiming its sporangia.

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Glomeromycetes The glomeromycetes (phylum Glomeromycota) were once considered zygomycetes They are now classified in a separate clade Glomeromycetes form a distinct type of endomycorrhizae called arbuscular mycorrhizae

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Ascomycetes Ascomycetes (phylum Ascomycota) live in marine, freshwater, and terrestrial habitats The phylum is defined by production of sexual spores in saclike asci, usually contained in fruiting bodies called ascocarps Ascomycetes vary in size and complexity, from unicellular yeasts to elaborate cup fungi and morels

LE The cup-shaped ascocarps (fruiting bodies) of Aleuria aurantia give this species its common name: orange peel fungus. The edible ascocarp of Morchella esculenta, the succulent morel is often found under trees in orchards. 10 µm Tuber melanosporum is a truffle, an ascocarp that grows underground and emits strong odors. These ascocarps have been dug up and the middle one sliced open. Neurospora crassa feeds as a mold on bread and other food (SEM).

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Sordaria

LE PLASMOGAMY Key Haploid (n) Dikaryotic (n + n) Diploid (2n) SEXUAL REPRODUCTION KARYOGAMY Four haploid nuclei MEIOSIS Dikaryotic hyphae extended from ascogonium ASEXUAL REPRODUCTION Diploid nucleus (zygote) Dispersal Germination Mycelium Mycelia Conidiophore Conidia; mating type (–) Mating type (+) Ascus (dikaryotic) Eight ascospores Asci Ascocarp Germination Dispersal

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Basidiomycetes Basidomycetes (phylum Basidiomycota) include mushrooms and shelf fungi The phylum is defined by a clublike structure called a basidium, a transient diploid stage in the life cycle

LE Fly agaric (Amanita muscoria), a common species in conifer forests in the northern hemisphere Maiden veil fungus (Dictyphora), a fungus with an odor like rotting meat Shelf fungi, important decomposers of wood Puffballs emitting spores

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The life cycle of a basidiomycete usually includes a long-lived dikaryotic mycelium In response to environmental stimuli, the mycelium reproduces sexually by producing elaborate fruiting bodies call basidiocarps Mushrooms are examples of basidiocarps

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The numerous basidia in a basidiocarp are sources of sexual spores called basidiospores Asexual reproduction is much less common in basidiomycetes than in ascomycetes

LE PLASMOGAMY Key Haploid (n) Dikaryotic (n + n) Diploid (2n) SEXUAL REPRODUCTION KARYOGAMY MEIOSIS Dikaryotic mycelium Basidium containing four haploid nuclei Dispersal and germination Basidium 1 µm Mating type (+) Mating type (–) Haploid mycelia Gills lined with basidia Basidiocarp (dikaryotic) Basidia (dikaryotic) Diploid nuclei Basidiospore Basidium with four appendages Basidiospores

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 31.5: Fungi have a powerful impact on ecosystems and human welfare

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Decomposers Fungi are efficient decomposers They perform essential recycling of chemical elements between the living and nonliving world

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Symbionts Fungi form symbiotic relationships with plants, algae, and animals All of these relationships have profound ecological effects

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Mycorrhizae Mycorrhizae are enormously important in natural ecosystems and agriculture They increase plant productivity RESULTS

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Fungus-Animal Symbiosis Some fungi share their digestive services with animals These fungi help break down plant material in the guts of cows and other grazing mammals Many species of ants and termites use the digestive power of fungi by raising them in “farms”

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Lichens Lichens are a symbiotic association of millions of photosynthetic microorganisms held in a mass of fungal hyphae

LE A fruticose (shrub-like) lichen A foliose (leaf-like) lichen Crustose (crust-like) lichens

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The fungal component of a lichen is most often an ascomycete Algae or cyanobacteria occupy an inner layer below the lichen surface

LE Fungal hyphae Algal cell Soredia Algal layer Fungal hyphae Ascocarp of fungus 10 µm

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Pathogens About 30% of known fungal species are parasites, mostly on or in plants Animals are much less susceptible to parasitic fungi than are plants The general term for a fungal infection in animals is mycosis

LE Corn smut on cornTar spot fungus of sycamore leavesErgots on rye

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Practical Uses of Fungi Humans eat many fungi and use others to make cheeses, alcoholic beverages, and bread Genetic research on fungi is leading to applications in biotechnology Antibiotics produced by fungi treat bacterial infections

LE Staphylococcus Penicillium Zone of inhibited growth

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