Objective: Kingdom Fungi

Fig. 31-1 Figure 31.1 Can you spot the largest organism in this forest?

Fungi Characteristics The most common body structures are multicellular filaments and single cells (yeasts) Eukaryotes Fungi are heterotrophs and absorb nutrients from outside of their body Cell walls of chitin Reproduce with spores (sexually and asexually)

Fungi are adapted for nutrition by absorption hyphae: tiny threads of cytoplasm surrounded by a plasma membrane and covered by a cell wall

Mycelium mycelium(mycelia): interwoven mat of hyphae Function: - Feeding structure Maximizes surface area within food

Reproductive structure Fig. 31-2 Reproductive structure Hyphae Spore-producing structures Figure 31.2 Structure of a multicellular fungus 20 µm Mycelium

Some fungi have hyphae divided into cells by septa, with pores allowing cell-to-cell movement of organelles Coenocytic fungi lack septa, continuous cytoplasm

Mycorrhizae are mutually beneficial relationships between fungi and plant roots What do the plants get? The fungus?

Fungi produce spores through sexual or asexual life cycles Fungi reproduce by producing vast numbers of spores, either sexually or asexually Fungi can produce spores from different types of life cycles

Haploid (n) Heterokaryotic (unfused nuclei from different parents) Fig. 31-5-1 Key Haploid (n) Heterokaryotic (unfused nuclei from different parents) Diploid (2n) Spore-producing structures Spores ASEXUAL REPRODUCTION Mycelium Figure 31.5 Generalized life cycle of fungi GERMINATION

Haploid (n) Heterokaryotic stage Heterokaryotic (unfused nuclei from Fig. 31-5-2 Key Haploid (n) Heterokaryotic stage Heterokaryotic (unfused nuclei from different parents) PLASMOGAMY (fusion of cytoplasm) Diploid (2n) KARYOGAMY (fusion of nuclei) Spore-producing structures Zygote SEXUAL REPRODUCTION Spores ASEXUAL REPRODUCTION Mycelium Figure 31.5 Generalized life cycle of fungi GERMINATION

Haploid (n) Heterokaryotic stage Heterokaryotic (unfused nuclei from Fig. 31-5-3 Key Haploid (n) Heterokaryotic stage Heterokaryotic (unfused nuclei from different parents) PLASMOGAMY (fusion of cytoplasm) Diploid (2n) KARYOGAMY (fusion of nuclei) Spore-producing structures Zygote SEXUAL REPRODUCTION Spores ASEXUAL REPRODUCTION Mycelium Figure 31.5 Generalized life cycle of fungi MEIOSIS GERMINATION GERMINATION Spores

Sexual Reproduction Fungal nuclei are normally haploid Sexual reproduction requires the fusion of hyphae from different mating types (plasmogamy) At first, nuclei don’t fuse, then when they do (karyogamy), diploid cells produced Meiosis occurs to produce spores (haploid)

Asexual Reproduction In addition to sexual reproduction, many fungi can reproduce asexually Molds produce haploid spores by mitosis and form visible mycelia

Fig. 31-6 2.5 µm Figure 31.6 Penicillium, a mold commonly encountered as a decomposer of food

Other fungi that can reproduce asexually are yeasts, which inhabit moist environments Instead of producing spores, yeasts reproduce asexually by simple cell division and the pinching of “bud cells” from a parent cell

Fig. 31-7 10 µm Parent cell Figure 31.7 The yeast Saccharomyces cerevisiae in several stages of budding (SEM) Bud

Many molds and yeasts have no known sexual stage Mycologists have traditionally called these deuteromycetes, or imperfect fungi

The ancestor of fungi was an aquatic, single-celled, flagellated protist Fungi and animals are more closely related to each other than they are to plants or other eukaryotes

UNICELLULAR, FLAGELLATED Nucleariids ANCESTOR Opisthokonts Chytrids Fig. 31-8 Animals (and their close protistan relatives) UNICELLULAR, FLAGELLATED ANCESTOR Nucleariids Opisthokonts Chytrids Figure 31.8 Fungi and their close relatives Fungi Other fungi

Fungi and animals evolved from a common flagellated unicellular ancestor and multicellularity arose separately in the two groups

The Move to Land Fungi were among the earliest colonizers of land and probably formed mutualistic relationships with early land plants

Figure 31.11 Fungal diversity Hyphae 25 µm Chytrids (1,000 species) Zygomycetes (1,000 species) Fungal hypha Glomeromycetes (160 species) Ascomycetes (65,000 species) Figure 31.11 Fungal diversity Basidiomycetes (30,000 species)

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Chytrids Chytrids (phylum Chytridiomycota) are found in freshwater and soil They can be decomposers, parasites, or mutualists Molecular evidence supports the hypothesis that chytrids diverged early in fungal evolution Chytrids are unique among fungi in having flagellated spores, called zoospores

Fig. 31-12 Figure 31.12 Flagellated chytrid zoospore (TEM) Flagellum 4 µm

Zygomycetes The zygomycetes (phylum Zygomycota) exhibit great diversity of life histories They include fast-growing molds, parasites, and commensal symbionts Sporangia: In asexual repro, the structure that produces haploid spores Zygosporangia - In sexual repro, Zygosporangia (diploid spores), which are resistant to freezing and drying, can survive unfavorable conditions

Key Haploid (n) Heterokaryotic (n + n) Diploid (2n) Mating Fig. 31-13-4 Key Haploid (n) Heterokaryotic (n + n) Diploid (2n) PLASMOGAMY Mating type (+) Gametangia with haploid nuclei Mating type (–) 100 µm Young zygosporangium (heterokaryotic) Rhizopus growing on bread SEXUAL REPRODUCTION Dispersal and germination Zygosporangium Sporangia KARYOGAMY Figure 31.13 The life cycle of the zygomycete Rhizopus stolonifer (black bread mold) Spores Diploid nuclei Sporangium ASEXUAL REPRODUCTION MEIOSIS Dispersal and germination 50 µm Mycelium

Fig. 31-14 Figure 31.14 Pilobolus aiming its sporangia 0.5 mm

Glomeromycetes Glomeromycetes form mycorrhizae Why is this important to plants?

Ascomycetes Ascomycetes (phylum Ascomycota) live in marine, freshwater, and terrestrial habitats The phylum is defined by production of sexual spores in saclike asci (ascus) Ascomycetes are commonly called sac fungi Ascomycetes vary in size and complexity from unicellular yeasts to elaborate cup fungi and morels

Tuber melanosporum, a truffle Fig. 31-16 Morchella esculenta, the tasty morel Tuber melanosporum, a truffle Figure 31.16 Ascomycetes (sac fungi)

Ascomycetes include plant pathogens, decomposers, and symbionts 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

Key Conidia; mating type (–) Haploid spores (conidia) Haploid (n) Fig. 31-17-4 Conidia; mating type (–) Haploid spores (conidia) Key Haploid (n) Dikaryotic (n + n) Diploid (2n) Dispersal Germination Mating type (+) ASEXUAL REPRODUCTION Hypha PLASMOGAMY Ascus (dikaryotic) Conidiophore Mycelia Dikaryotic hyphae Mycelium Germination SEXUAL REPRODUCTION KARYOGAMY Dispersal Diploid nucleus (zygote) Asci Eight ascospores Ascocarp Figure 31.17 The life cycle of Neurospora crassa, an ascomycete Four haploid nuclei MEIOSIS

Basidiomycetes Basidomycetes (phylum Basidiomycota) include mushrooms, puffballs, and shelf fungi, mutualists, and plant parasites The phylum is defined by a clublike structure called a basidium, a diploid stage in the life cycle The basidiomycetes are also called club fungi

Fig. 31-18 Maiden veil fungus (Dictyphora), a fungus with an odor like rotting meat Puffballs emitting spores Shelf fungi, important decomposers of wood Figure 31.18 Basidiomycetes (club fungi)

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 The numerous basidia in a basidiocarp are sources of sexual spores called basidiospores

Dikaryotic mycelium Haploid mycelia Mating type (–) Mating type (+) Fig. 31-19-4 Dikaryotic mycelium Haploid mycelia PLASMOGAMY Mating type (–) Mating type (+) Gills lined with basidia Haploid mycelia SEXUAL REPRODUCTION Basidiocarp (n+n) Dispersal and germination Basidiospores (n) Basidium with four basidiospores Basidia (n+n) Basidium Figure 31.19 The life cycle of a mushroom-forming basidiomycete Basidium containing four haploid nuclei KARYOGAMY MEIOSIS Key Haploid (n) Dikaryotic (n +n) Diploid nuclei 1 µm Basidiospore Diploid (2n)

Fungi as Decomposers Fungi are efficient decomposers They perform essential recycling of chemical elements between the living and nonliving world

Fungus-Plant Mutualisms Mycorrhizae are enormously important in natural ecosystems and agriculture Plants harbor harmless symbiotic endophytes that live inside leaves or other plant parts Endophytes make toxins that deter herbivores and defend against pathogens

Fungus-Animal Symbioses Some fungi share their digestive services with animals These fungi help break down plant material in the guts of cows and other grazing mammals

Fig. 31-22 Figure 31.22 Fungus-gardening insects For the Discovery Video Leafcutter Ants, go to Animation and Video Files.

Lichens A lichen is a symbiotic association between a photosynthetic microorganism and a fungus in which millions of photosynthetic cells are held in a mass of fungal hyphae

Crustose (encrusting) lichens A foliose (leaflike) lichen Fig. 31-23  Crustose (encrusting) lichens A fruticose (shrublike) lichen  A foliose (leaflike) lichen Figure 31.23 Variation in lichen growth forms

The fungal component of a lichen is most often an ascomycete Algae or cyanobacteria occupy an inner layer below the lichen surface

Lichens are important pioneers on new rock and soil surfaces Lichens are sensitive to pollution, and their death can be a warning that air quality is deteriorating http://dsc.discovery.com/videos/planet-earth-jungles-growing-fungi.html

Disease-causing fungi 30% of fungi are parasitic Yeast infections Ringworm Athlete’s Foot

Fungi as Pathogens About 30% of known fungal species are parasites or pathogens, mostly on or in plants Some fungi that attack food crops are toxic to humans Animals are much less susceptible to parasitic fungi than are plants The general term for a fungal infection in animals is mycosis http://www.youtube.com/watch?v=SXk3bqLecQ8

(a) Corn smut on corn (b) Tar spot fungus on maple leaves Fig. 31-25 Figure 31.25 Examples of fungal diseases of plants For the Discovery Video Fungi, go to Animation and Video Files. (a) Corn smut on corn (b) Tar spot fungus on maple leaves (c) Ergots on rye

Practical Uses of Fungi Humans eat many fungi and use others to make cheeses, alcoholic beverages, and bread Some fungi are used to produce antibiotics for the treatment of bacterial infections, for example the ascomycete Penicillium

Staphylococcus Penicillium Zone of inhibited growth Fig. 31-26 Figure 31.26 Fungal production of an antibiotic

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