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Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece.

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Presentation on theme: "Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece."— Presentation transcript:

1 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

2 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

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

4 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

5 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

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

7 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

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

9 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Some fungi have hyphae divided into cells by septa, with pores allowing cell-to-cell movement Coenocytic fungi lack septa

10 LE 31-3 Nuclei Septate hypha Septum Pore Cell wall Nuclei Coenocytic hypha

11 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Some unique fungi have specialized hyphae that allow them to penetrate the tissues of their host

12 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

13 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

14 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

15 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

16 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

17 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Hours, days, or even centuries may pass before the occurrence of karyogamy, nuclear fusion During karyogamy, the haploid nuclei fuse, producing diploid cells The diploid phase is short-lived and undergoes meiosis, producing haploid spores

18 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

19 LE µm

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

21 LE m Parent cell Bud

22 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

23 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

24 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

25 LE µm

26 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

27 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

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

29 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

30 LE Hyphae 25 µm Flagellum 4 µm

31 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Video: Allomyces Zoospore Release Video: Allomyces Zoospore Release Video: Phlyctochytrium Zoospore Release Video: Phlyctochytrium Zoospore Release

32 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Until recently, systematists thought that fungi lost flagella only once in their evolutionary history Molecular data indicate that some “chytrids” are actually more closely related to another fungal group, the zygomycetes

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

34 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

35 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

36 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Zygosporangia, which are resistant to freezing and drying, can survive unfavorable conditions Some zygomycetes, such as Pilobolus, can actually “aim” their sporangia toward conditions associated with good food sources

37 LE mm

38 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Microsporidia Microsporidia are unicellular parasites of animals and protists They are now classified as zygomycetes

39 LE µm Spore Developing microsporidian Host cell nucleus

40 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

41 LE µm

42 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

43 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).

44 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Ascomycetes reproduce asexually by enormous numbers of asexual spores called conidia Conidia are not formed inside sporangia; they are produced asexually at the tips of specialized hyphae called conidiophores

45 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

46 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

47 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

48 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

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

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

51 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

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

53 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

54 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

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

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

57 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”

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

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

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

61 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

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

63 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

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

65 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

66 LE Staphylococcus Penicillium Zone of inhibited growth

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


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