1. Teresa Audesirk • Gerald Audesirk • Bruce E. Byers
Biology: Life on Earth
Eighth Edition
Lecture for Chapter 22
The Diversity of Fungi
Copyright © 2008 Pearson Prentice Hall, Inc.

2. These honey mushrooms are part of the visible portion of the largest organism on Earth.
A single honey mushroom colony in Oregon covers and area of 8.9 sq. km (2200 acres).
Figure: 20-CO
Title:
The Diversity of Fungi
Caption:

3. Chapter 22 Outline 22.1 What Are the Key Features of Fungi? p. 424
22.2 What Are the Major Groups of Fungi? p. 425
22.3 How Do Fungi Interact with Other Species? p. 430
22.4 How Do Fungi Affect Humans? p. 433

4. Section 22.1 Outline 22.1 What Are the Key Features of Fungi?
Fungal Bodies Consist of Slender Threads
Fungi Obtain Their Nutrients from Other Organisms
Fungi Propagate by Spores
Most Fungi Can Reproduce Both Sexually and Asexually

5. Fungal Body Structure Most fungi are multicellular
Cells are surrounded by cell walls composed of chitin, a nitrogen-containing polysaccharide
Body of almost all fungi is a mycelium, an interwoven mass of threadlike filaments called hyphae (singular, hypha)

6. FIGURE 22-1 (part 1) The filamentous body of a fungus
(a) A fungal mycelium spreads over decaying vegetation. The mycelium is composed of (b) a tangle of microscopic hyphae, only one cell thick, portrayed in cross section (c) to show their internal organization.

7. Fungal Body Structure
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
Hyphae of some fungi lack septa, consisting of single elongated cells with hundreds or thousands of nuclei
The nuclei of most species are haploid

8. FIGURE 22-1 (part 2) The filamentous body of a fungus
The mycelium is composed of (b) a tangle of microscopic hyphae, only one cell thick, portrayed in cross section (c) to show their internal organization.

9. Nutrition and Fungal Lifestyles
All are heterotrophic
Secrete enzymes outside their bodies and absorb the digested nutrients
Have diverse lifestyles
Fungal decomposers (saprobes) 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

10. Propagate by Spores
Spores are haploid reproductive cells capable of developing into an adult fungus
Usually produced in large numbers
Dispersed by animals or air currents
Both asexual and sexual reproduction involve the production of spores within fruiting bodies

11. FIGURE 22-2 Some fungi can eject spores
A ripe earthstar mushroom, struck by a drop of water, releases a cloud of spores from the fruiting body that will be dispersed by air currents.

12. Asexual Reproduction Typically occurs under stable conditions
Can occur either by:
Fragmentation of the mycelium
Asexual spore formation
Haploid mycelium produces haploid asexual spores by mitosis
Spores germinate and develop into a new mycelium by mitosis
Results in the rapid production of genetically identical clones

13. Sexual Reproduction
Typically occurs under conditions of environmental change or stress
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
Zygote undergoes meiosis to form haploid sexual spores

14. Sexual Reproduction
Spores germinate and develop into a new mycelium by mitosis
Results in the production of genetically diverse fungal bodies

15. Section 22.2 Outline 22.2 What Are the Major Groups of Fungi?
Chytrids Produce Swimming Spores
Zygomycetes Can Reproduce by Forming Diploid Spores
Ascomycetes Form Spores in a Saclike Case
Basidiomycetes Produce Club-Shaped Reproductive Structures
Some Fungi Form Symbiotic Relationships

16. Classification of Fungi
Fungi have been assigned to four phyla based upon the way they produce sexual spores
Chytridiomycota (chytrids)
Zygomycota (zygote fungi)
Ascomycota (sac fungi)
Basidiomycota (club fungi)

17. FIGURE 22-3 Evolutionary tree of the major groups of fungi

18. Table 22-1 The Phyla of Fungi

19. The Chytrids The Chytrids Most are aquatic
Reproduce both asexually and sexually
Form flagellated spores that require water for dispersal
Figure 22-4, p. 426, illustrates the chytrid fungus Allomyces in the midst of sexual reproduction

20. FIGURE 22-4 Chytrid filaments
These filaments of the chytrid fungus Allomyces are in the midst of sexual reproduction. The orange structures visible on many of the filaments will release male gametes; the clear structures will release female gametes. Chytrid gametes are flagellated, and these swimming reproductive structures aid dispersal of members of this mostly aquatic phylum

21. The Chytrids 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
According to evolutionists, primitive chytrids are believed to have given rise to the other groups of modern fungi

22. Zygomycetes Most live in soil or on decaying plant or animal material
Reproduce both asexually and sexually
Sexual spores are thick-walled zygospores
During asexual reproduction:
Haploid spores are produced via mitosis in black spore cases called sporangia
Spores disperse and germinate to form new haploid hyphae
Figure 20-5, p. 427, depicts the asexual reproduction in Rhizopus, black bread mold

23. The life cycle of a zygomycete
FIGURE 22-5
The life cycle of a zygomycete
Top: in asexual reproduction in the black bread mold (genus Rhizopus), haploid spores, produced within sporangia, disperse and germinate on food such as bread. Bottom: During sexual reproduction, hyphae of different mating types (designated + and - on the bread) contact one another and fuse, producing a diploid zygospore. The zygospore undergoes meiosis and germinates, producing sporangia that liberate haploid spores.

24. Ascomycetes
Live in a variety of marine, freshwater, and terrestrial habitats
Each fruiting body contains numerous saclike cases called asci (singular, ascus)
Reproduce both asexually and sexually
Sexual spores form in saclike asci

25. FIGURE 22-7a Diverse ascomycetes
The cup-shaped fruiting body of the scarlet cup fungus (top)
The morel (bottom), an edible delicacy. (Consult an expert before sampling any wild fungus – some are deadly!)
. (Consult an expert before sampling any wild fungusｴsome are deadly!)

26. FIGURE 22-6 The life cycle of a typical ascomycete
Top: In ascomycete asexual reproduction, haploid hyphae give rise to stalked structures that produce haploid spores. Bottom: In sexual reproduction, haploid nuclei of different mating types fuse to form diploid zygotes that divide and give rise to haploid ascospores.

27. Ascomycetes Better known examples include
Most of the food-spoiling molds
Morels and truffles (edible delicacies)
Penicillium, the mold that produces penicillin (the first antibiotic)
Yeasts (single-celled fungi)

28. Basidiomycetes
Live in a variety of marine, freshwater, and terrestrial habitats
Each fruiting body contains numerous club-shaped structures called basidia (singular, basidium)
Usually reproduce sexually
Sexual spores form in club-shaped basidia
Figure 22-9, p. 429, depicts an overview of sexual reproduction in a basidiomycetes

29. FIGURE 22-8 The life cycle of a typical basidiomyce

30. Diverse basidiomycetes
FIGURE 22-9b
Diverse basidiomycetes
(b) Shelf fungi, some the size of dessert plates, are conspicuous on trees. F
FIGURE 22-9a
Diverse basidiomycetes
(a) The giant puffball Lycopedon giganteum may produce up to 5 trillion spores.

31. FIGURE 22-9c Diverse basidiomycetes
(c) The spores of stinkhorns are carried on the outside of a slimy cap that smells terrible to humans, but appeals to flies. The flies lay their eggs on the stinkhorn, and inadvertently disperse the spores that stick to their bodies.

32. Basidiomycetes Better known examples include
Mushrooms (some are edible, others are poisonous)
Puffballs
Shelf fungi (decomposers of wood)
Stinkhorns
Rusts and smuts (plant parasites)
Yeasts

33. Fairy Rings A fairy ring is a circular pattern of mushroom growth
Fairy rings form at the leading edge of an expanding underground fungal mycelium
The wider the diameter of the ring, the older the mycelium
Some fairy rings are estimated to be 700 years old

34. FIGURE 22-10 A mushroom fairy ring
Mushrooms emerge in a fairy ring from an underground fungal mycelium, growing outward from a central point where a single spore germinated, perhaps centuries ago.

35. Section 22.3 Outline 22.3 How Do Fungi Interact with Other Species?
Lichens Are Formed by Fungi That Live with Photosynthetic Algae or Bacteria
Mycorrhizae Are Fungi Associated with Plant Roots
Endophytes Are Fungi That Live Inside Plant Stems and Leaves
Some Fungi Are Important Recyclers

36. Symbiotic Relationships
A symbiosis 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 (a parasite of plants or animals) or beneficial (lichens and mycorrhizae)

37. Lichens
Lichens are symbiotic associations between fungi (usually an ascomycete) and algae or cyanobacteria
Fungus provides photosynthetic partner with shelter and protection
Photosynthetic partner provides fungus with food (sugar)

38. FIG 22-11 The lichen: A symbiotic partnership
Most lichens have a layered structure bounded on the top and bottom by an outer layer formed from fungal hyphae. The fungal hyphae emerge from the lower layer, forming attachments that anchor the lichen to a surface, such as a rock or a tree. An algal layer in which the alga and fungus grow in close association lies beneath the upper layer of hyphae.

39. Lichens
Grow on a wide variety of materials (soils, tree trunks and branches, rocks, fences, roofs, and walls)
Are able to survive environmental extremes (newly formed volcanic islands, deserts)
Are very diverse in form

40. FIG 22-12a Diverse lichens
(a) A colorful encrusting lichen, growing on dry rock, illustrates the tough independence of this symbiotic combination of fungus and algae.
(b) A leafy lichen grows from a dead tree branch.

41. Mycorrhizae
Mycorrhizae (singular, mycorrhiza) are symbiotic associations between fungi and plant roots
Fungus provides plant with water, minerals, and organic nutrients it absorbs from the soil
Plant provides fungus with food (sugar)
80% of plants with roots have mycorrhizae
Relationship may have helped plants colonize land

42. FIGURE 22-13 Mycorrhizae enhance plant growth
Hyphae of mycorrhizae entwining about the root of an aspen tree. Plants grow significantly better in a symbiotic association with these fungi, which help make nutrients and water available to the roots.

43. Endophytes
Endophytes are fungi that live inside the above-ground tissues of plants
Some are parasites that cause plant diseases
Some are beneficial to host plants
Some ascomycete species live inside grasses and produce substances that are distasteful or toxic to insects and grazing mammals, protecting the grasses from predation

44. Recyclers
Fungi are Earth’s undertakers, feeding on the dead of all kingdoms
Fungal saprophytes (feeding on dead organisms) release extracellular substances that digest the tissues of the dead and liberate carbon, nitrogen, phosphorus compounds, and minerals that can be reused by plants

45. Section 22.4 Outline 22.4 How Do Fungi Affect Humans?
Fungi Attack Plants That Are Important to People
Fungi Cause Human Diseases
Fungi Can Produce Toxins
Many Antibiotics Are Derived from Fungi
Fungi Make Important Contributions to Gastronomy
Fungal Ingenuity

46. Fungi Attack Plants
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

47. FIGURE Corn smut
This basidiomycete pathogen destroys millions of dollars' worth of corn each year. Even a pest like corn smut has its admirers, though. In Mexico this fungus is known as huitlacoche and is considered to be a great delicacy.

48. Fungi Attack Plants
Fungi can destroy plant material that has been harvested for human use
Cause wooden structures to rot
Damage cotton and wool fabrics

49. Fungi Attack Plants Some fungi benefit agriculture
Used to control insect pests such as rice weevils, tent caterpillars, aphids, citrus mites, and grasshoppers
Fungi identified that attack mosquitoes that transmit malaria

50. FIGURE 22-15a Helpful fungal parasites
Fungal pathogens can be helpful to humans. For example, fungi such as (a) the Cordyceps species that has killed this grasshopper are used by farmers to control insect pests.

51. FIGURE 22-15b Helpful fungal parasites
(b) Some fungi might one day be used to help protect humans from disease. A malaria-carrying mosquito infected by Beauveria species is transformed from a healthy animal (top) to a fungus-encrusted corpse in less than two weeks.

52. Fungi Cause Human Diseases
Athlete’s foot, jock itch, and ringworm are caused by fungi that attack the skin
Valley fever and histoplasmosis are caused by fungi that attack the lungs
Infection occurs when victim inhales spores

53. Fungi Cause Human Diseases
Most vaginal infections are caused by the yeast Candida albicans

54. FIGURE 22-16 The unusual yeast
Yeasts are unusual, normally non-filamentous ascomycetes that reproduce most commonly by budding. The yeast shown here is Candida, a common cause of vaginal infections.

55. Fungi Produce Toxins
Molds of the genus Aspergillus produce aflatoxins, highly toxic, carcinogenic compounds
Infect foods such as peanuts

56. Fungi Produce Toxins
Claviceps purpurea (an ascomycete) produces several toxins
Infects rye plants and causes ergot disease
Symptoms of ergot poisoning include vasoconstriction of blood vessels, vomiting, convulsive twitching, hallucinations, and death

57. Fungi Produce Antibiotics
Penicillin
First antibiotic to be discovered
Used to combat bacterial diseases

58. FIGURE Penicillium
Penicillium growing on an orange. Reproductive structures, which coat the fruit's surface, are visible, while hyphae beneath draw nourishment from inside. The antibiotic penicillin was first isolated from this fungus.

59. Fungi Produce Other Drugs
Cyclosporin
Used to suppress the immune response during organ transplants

60. Fungi Contribute to Gastronomy
Certain ascomycete molds impart flavor to some of the world’s most famous cheeses
Roquefort
Camembert
Stilton
Gorgonzola

61. Fungi Contribute to Gastronomy
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

62. Fungi Contribute to Gastronomy
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

63. Fungi Contribute to Gastronomy
Some fungi are consumed directly
Mushrooms (a basidiomycete)
Morels (an ascomycete)
Truffles (an ascomycete)

64. FIGURE The truffle
Truffles, rare ascomycetes (each about the size of a small apple), are a gastronomic delicacy.

65. Fungal Ingenuity
The truffle has evolved an effective adaptation for dispersal of its spores
Releases an odor which causes pigs and other animals to dig it up, scattering spores to the winds
The zygomycete Pilobolus has evolved bulb tops that blast off, spreading spores

66. FIGURE 22-19 An explosive zygomycete
The delicate, translucent reproductive structures of the zygomycete Pilobolus literally blow their tops when ripe, dispersing the black caps with their payload of spores.

67. Fungal Ingenuity
Arthrobotrys cleverly traps and “strangles” microscopic roundworms called nematodes to obtain nutrients

68. FIGURE 22-20 Nemesis of nematodes
Arthrobotrys, the nematode (roundworm) strangler, traps its prey in a noose-like modified hypha that swells when the inside of the loop is contacted.