1. Fungi
Chapter 20
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2. Differences Between Fungi and Plants Fungi are Heterotrophs.
A Fungus Is Not A Plant
Differences Between Fungi and Plants
Fungi are Heterotrophs.
Fungi Have Filamentous Bodies.
Fungi Have Unusual Reproductive Modes.
Fungi Have Cell Walls Made of Chitin.
Fungi Have Nuclear Mitosis.
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3. The Body of a Fungus Fungal Septum
Fungi exist mainly in the form of slender filaments (hyphae).
Long chains of cells joined end-to-end divided by cross-walls (septa).
Rarely form complete barrier.
Cytoplasm freely streams in hyphae.
Mycelium - Mass of connected hyphae.
Grows through and penetrates substrate.
Fungal Septum
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4. Fungi cell walls are formed of polysaccharides and chitin.
The Body of a Fungus
Fungi cell walls are formed of polysaccharides and chitin.
Not cellulose like those of plants.
Mitosis is unique.
Nuclear envelope does not break down and re-form.
Spindle apparatus formed within.
Spindle plaques take place of centrioles.
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5. Fungi are capable of both sexual and asexual reproduction.
How Fungi Reproduce
Fungi are capable of both sexual and asexual reproduction.
Fungi reproduce sexually after two hyphae of opposite mating type fuse.
Heterokaryotic hypha - Fungal hypha containing nuclei derived from two genetically distinct individuals.
Homokaryotic - All nuclei are genetically similar.
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6. Dikaryotic - Two distinct nuclei within each hyphae compartment.
How Fungi Reproduce
Dikaryotic - Two distinct nuclei within each hyphae compartment.
Monokaryotic - Each compartment has a single nucleus.
Reproductive Structures
Sporangia - Involved in spore formation.
Gametangia - Gametes are formed within.
Conidiophores - Produce asexual spores (Conidia).
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7. How Fungi Obtain Nutrients
All fungi obtain food by secreting digestive enzymes and then absorbing the organic molecules produced (external digestion).
Extensive hyphae network provides enormous surface area for absorption.
Many fungi are able to break down cellulose in wood.
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8. Fungi and bacteria are the principal decomposers in the biosphere.
Ecology of Fungi
Fungi and bacteria are the principal decomposers in the biosphere.
Mineral Cycling
Fungi are virtually the only organisms capable of breaking down lignin (a complex chemical found in plant cell walls)
Fungi often act as disease-causing organisms for both plants and animals.
Agricultural Damage
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9. Many can be used to break down complex substances.
Ecology of Fungi
Manufacture of bread and beer dependent on biochemical activities of yeasts.
Cheese and wine.
Many can be used to break down complex substances.
Mutualistic Associations
Lichens - Fungi and green algae.
Mycorrhizae - Fungi and plant roots.
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10. Three Phyla of Fungi
Three phyla of fungi are distinguished primarily by their sexual reproductive structures.
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11. Phylum Zygomycota Smallest of three phyla. (Bread molds)
Produces temporarily dormant zygosporangia.
Sexual reproduction occurs by fusion of gametangia.
Asexual Reproduction most common.
Hyphae produce clumps of erect stalks sporangiophores.
Form sporangia.
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12. Phylum Ascomycota
Very large group including yeasts, common molds, and morels.
Named for reproductive structure ascus.
Haploid zygotic nucleus formed within.
Asci differentiated with ascocarp.
Asexual reproduction takes place in conidia spores at the end of conidiophores.
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13. Phylum Ascomycota Hyphae may be either homokaryotic or heterokaryotic.
Female gametangia - ascogonia.
Male gametangia - antheridium.
Yeasts
Unicellular - Most reproduction is asexual and takes place by cell fission or budding.
Ferment carbohydrates.
Play a leading role in genetic research.
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14. Phylum Basidiomycota
Most familiar fungi. - Mushrooms, toadstools, puffballs, rusts, and smuts.
Named for characteristic sexual reproductive structure, basidium.
Four halpoid products of meiosis are incorporated into basidiospores.
Borne on sterigmata.
Mycelium made up of primary and secondary mycelium.
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15. Deuteromycetes - Sexual reproductive stages have not been observed.
The Imperfect Fungi
Deuteromycetes - Sexual reproductive stages have not been observed.
Economically important genera:
Penicillium - Penicillin
Aspergillus - Soy Sauce
Aflotoxins (carcinogens) produced by some Aspergillus flavus strains growing on corn and peanuts.
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16. Extremely sensitive to pollutants.
Lichens
Lichens are symbiotic associations between a fungus and a photosynthetic partner.
Usually ascomycetes.
Specialized fungal hyphae penetrate photosynthetic cells and transfer nutrients to fungal partner.
Durable fungus, combined with photosynthetic properties, has enabled lichens to invade harsh climates.
Extremely sensitive to pollutants.
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17. Mycorrhizae
Roots of about 90% of all kinds of vascular plants are involved in mutualistic symbiotic relationships (mycorrhizae).
Endomycorrhizae - Fungal hyphae penetrate outer cells of plant root.
Most common
Ectomycorrhizae - Hyphae surround, but do not penetrate, cell walls of roots.
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18. Copyright © McGraw-Hill Companies Permission required for reproduction or display
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