1. Chapter 31
Fungi

3. Concept 31.1: Nutrition and Fungal Lifestyles
Fungi are heterotrophs but do not ingest their food
Fungi secrete into their surroundings exoenzymes that break down complex molecules
And then absorb the remaining smaller compounds

4. Fungi exhibit diverse lifestyles
Decomposers
Parasites
Mutualistic symbionts

5. The morphology of multicellular fungi
Body Structure
The morphology of multicellular fungi
Enhances their ability to absorb nutrients from their surroundings
Hyphae. The mushroom and its subterranean mycelium are a continuous network of hyphae.
Reproductive structure. The mushroom produces tiny cells called spores.
Spore-producing structures
20 m
Mycelium
Figure 31.2

6. Fungi consist of Most fungi
Mycelia, networks of branched hyphae adapted for absorption
Most fungi
Have cell walls made of chitin, unlike plant cells

7. Some fungi Coenocytic fungi
Have hyphae divided into cells by septa, with pores allowing cell-to-cell movement of materials
Coenocytic fungi
Lack septa
Cell wall
Cell wall
Nuclei
Pore
Septum
Nuclei
Figure 31.3a, b
(a) Septate hypha
(b) Coenocytic hypha

8. Mycorrhizae
Are mutually beneficial relationships between fungi and plant roots
Fungal hyphae between plant cells
(colorized SEM)
100 m
mycorrhizae
mycorrhizae
Figure 37.12a

9. Fungi propagate themselves
Concept 31.2:
Fungi propagate themselves
By producing vast numbers of spores, either sexually or asexually

10. The sexual life cycle involves
Sexual Reproduction
The sexual life cycle involves
Cell fusion, plasmogamy
Nuclear fusion, karyogamy
An intervening heterokaryotic stage
Occurs between plasmogamy and karyogamy in which cells have haploid nuclei from two parents

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

12. Many molds and yeasts have no known sexual stage
Asexual Reproduction
Many molds and yeasts have no known sexual stage
Mycologists have traditionally called these imperfect fungi
10 m
Parent cell
Bud
Figure 31.7
2.5 m
Figure 31.6

13. Concept 31.3: The Origin of Fungi Molecular evidence
Supports the hypothesis that fungi and animals diverged from a common ancestor that was unicellular and bore flagella

14. The oldest undisputed fossils of fungi
Are only about 460 million years old
50 m
Figure 31.8 

15. Fungi were among the earliest colonizers of land
The Move to Land
Fungi were among the earliest colonizers of land
Probably as symbionts with early land plants

16. Concept 31.4: Fungi have radiated into a diverse set of lineages
Much of their phylogeny is still uncertain
Molecular analysis has helped clarify the evolutionary relationships between fungal groups

17. Arbuscular mycorrhizal fungi
The phylogeny of fungi
Chytrids
Zygote fungi
Arbuscular mycorrhizal fungi
Sac fungi
Club fungi
Chytridiomycota
Zygomycota
Glomeromycota
Ascomycota
Basidiomycota
Figure 31.9

18. A review of fungal phyla
Table 31.1

19. Fungi in the phylum Zygomycota, the zygomycetes
Include fast-growing molds, parasites, and commensal symbionts
Are named for their sexually produced zygosporangia

20. The life cycle of Rhizopus stolonifer
Is fairly typical of zygomycetes
Mycelia have various mating types (here designated +, with red nuclei, and , with blue nuclei). 1
Neighboring mycelia of different mating types form hyphal extensions called gametangia, each walled off around several haploid nuclei by a septum. 2
Rhizopus growing on bread
ASEXUAL REPRODUCTION
Mycelium
Dispersal and germination
MEIOSIS
KARYOGAMY
PLASMOGAMY
Key
Haploid (n)
Heterokaryotic (n + n)
Diploid
Sporangium
Diploid nuclei
Zygosporangium (heterokaryotic)
100 m
Young zygosporangium (heterokaryotic)
SEXUAL REPRODUCTION
Mating type (+)
Mating type ()
Gametangia with haploid nuclei
50 m
Sporangia
A heterokaryotic zygosporangium forms, containing multiple haploid nuclei from the two parents. 3
The spores germinate and grow into new mycelia. 8 9
Mycelia can also reproduce asexually by forming sporangia that produce genetically identical haploid spores.
The sporangium disperses genetically diverse, haploid spores. 7 4
This cell develops a rough, thick-walled coating that can resist dry environments and other harsh conditions for months. 5
When conditions are favourable, karyogamy occurs, followed by meiosis. 6
The zygosporangium then breaks dormancy, germinating into a short sporangium.
Figure 31.12

21. Some zygomycetes, such as Pilobolus
Can actually “aim” their sporangia toward conditions associated with good food sources
0.5 mm
Figure 31.13

22. Zygosporangia, which are resistant to freezing and drying
Are capable of persisting through unfavorable conditions
Can undergo meiosis when conditions improve

23. Glomeromycetes
Form a distinct type of endomycorrhizae called arbuscular mycorrhizae
90% of all plants form mycorrhizae with glomeromycetes
2.5 m
Figure 31.15

24. Fungi in the phylum Ascomycota
Ascomycetes
Fungi in the phylum Ascomycota
Are found in a variety of marine, freshwater, and terrestrial habitats
Are defined by the production of sexual spores in saclike asci, which are usually contained in fruiting bodies called ascocarps

25. Ascomycetes
Vary in size and complexity from unicellular yeasts to elaborate cup fungi and morels
(a) The cup-shaped ascocarps (fruiting bodies) of Aleuria aurantia give this species its common name: orange peel fungus.
(b) The edible ascocarp of Morchella esculenta, the succulent morel, is often found under trees in orchards.
(c) 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.
(d) Neurospora crassa feeds as a mold on bread and other food (SEM).
10 m
Figure 31.16a–d

26. Ascomycetes can reproduce
Asexually by producing enormous numbers of asexual spores called conidia

27. A dikaryotic ascus develops.
Ascomycetes
The life cycle of Neurospora crassa, an ascomycete
Ascomycete mycelia can also reproduce asexually by producing haploid conidia. 7
Dispersal
ASEXUAL REPRODUCTION
Germination
Mycelium
Conidiophore
Mycelia
Asci
Eight ascospores
Ascocarp
Four haploid nuclei
MEIOSIS
KARYOGAMY
PLASMOGAMY
SEXUAL REPRODUCTION
Diploid nucleus (zygote)
Ascogonium
Ascus (dikaryotic)
Dikaryotic hyphae
Mating type ()
Conidia; mating type ()
Key
Haploid (n)
Dikaryotic (n  n)
Diploid (2n)
Neurospora can reproduce sexually by producing specialized hyphae. Conidia of the opposite mating type fuse to these hyphae. 1
A dikaryotic ascus develops. 2
Karyogamy occurs within the ascus, producing a diploid nucleus. 3
The developing asci are contained in an ascocarp. The ascospores are discharged forcibly from the asci through an opening in the ascocarp. Germinating ascospores give rise to new mycelia. 6 5
Each haploid nucleus divides once by mitosis, yielding eight nuclei. Cell walls develop around the nuclei, forming ascospores (LM).
The diploid nucleus divides by meiosis, yielding four haploid nuclei. 4
Figure 31.17

28. Fungi in the phylum Basidiomycota
Basidiomycetes
Fungi in the phylum Basidiomycota
Include mushrooms and shelf fungi
Are defined by a clublike structure called a basidium, with a transient diploid stage in the life cycle

29. Basidiomycetes Figure 31.18a–d
(a) Fly agaric (Amanita muscaria), a common species in conifer forests in the northern hemisphere
(b) Maiden veil fungus (Dictyphora), a fungus with an odor like rotting meat
(c) Shelf fungi, important decomposers of wood
(d) Puffballs emitting spores
Figure 31.18a–d

30. The life cycle of a basidiomycete
Usually includes a long-lived dikaryotic mycelium, which can erect its fruiting structure, a mushroom, in just a few hours
Figure Fairy Ring

31. The life cycle of a mushroom-forming basidiomycete
A dikaryotic mycelium forms, growing faster then, and ultimately crowding out, the haploid parental mycelia. 2
Two haploid mycelia of different mating types undergo plasmogamy. 1
PLASMOGAMY
Dikaryotic mycelium
Basidiocarp (dikaryotic)
KARYOGAMY
Key
MEIOSIS
Gills lined with basidia
SEXUAL REPRODUCTION
Mating type ()
Mating type ()
Haploid mycelia
Dispersal and germination
Basidiospores
Basidium with four appendages
Basidium containing four haploid nuclei
Basidia (dikaryotic)
Diploid nuclei
Basidiospore
1 m
Basidium
Haploid (n)
Dikaryotic (n  n)
Diploid (2n) 3
Environmental cues such as rain or temperature changes induce the dikaryotic mycelium to form compact masses that develop into basidiocarps (mushrooms, in this case).
In a suitable environment, the basidiospores germinate and grow into short-lived haploid mycelia. 8
When mature, the basidiospores are ejected, fall from the cap, and are dispersed by the wind. 7
The basidiocarp gills are lined with terminal dikaryotic cells called basidia. 4
Each diploid nucleus yields four haploid nuclei. Each basidium grows four appendages, and one haploid nucleus enters each appendage and develops into a basidiospore (SEM). 6
Karyogamy in the basidia produces diploid nuclei, which then undergo meiosis. 5
Figure 31.20

32. Concept 31.5:
Fungi have a powerful impact on ecosystems and human welfare

33. Fungi are decomposers of organic material
Performing essential recycling of chemical elements between the living and nonliving world

34. Fungi form symbiotic relationships with
Symbionts
Fungi form symbiotic relationships with
Plants, algae, and animals

35. Mycorrhizae Mycorrhizae
Are enormously important in natural ecosystems and agriculture
Increase plant productivity
Researchers grew soybean plants in soil treated with fungicide (poison that kills fungi) to prevent the formation of mycorrhizae in the experimental group. A control group was exposed to fungi that formed mycorrhizae in the soybean plants’ roots.
EXPERIMENT
The soybean plant on the left is typical of the experimental group. Its stunted growth is probably due to a phosphorus deficiency. The taller, healthier plant on the right is typical of the control group and has mycorrhizae.
CONCLUSION
These results indicate that the presence of mycorrhizae benefits a soybean plant and support the hypothesis that mycorrhizae enhance the plant’s ability to take up phosphate and other needed minerals.
Figure 31.21
RESULTS
RESULTS

36. Fungus-Animal Symbiosis
Some fungi share their digestive services with animals
Helping break down plant material in the guts of cows and other grazing mammals

37. Many species of ants and termites take advantage of the digestive power of fungi by raising them in “farms”
Figure 31.22

38. Lichens
Are a symbiotic association of fungal hyphae with algae or cyanobacteria
Ascocarp of fungus
Fungal
hyphae
Algal
layer
Soredia
Algal cell
Fungal hyphae
10 m
Figure 31.24

39. Lichens Are classified in three broad groups Figure 31.23a–c
(a) A fruticose (shrub-like) lichen
(b) A foliose (leaf-like) lichen
(c) Crustose (crust-like) lichens
Figure 31.23a–c

40. (b) Tar spot fungus on maple leaves
Pathogens
About 30% of known fungal species
Are parasites, mostly on or in plants
(a) Corn smut on corn
(b) Tar spot fungus on maple leaves
(c) Ergots on rye
Figure 31.25a–c

41. Practical Uses of Fungi
Humans eat many fungi
And use others to make cheeses, alcoholic beverages, and bread

42. Antibiotics produced by fungi treat bacterial infections (i. e
Antibiotics produced by fungi treat bacterial infections (i.e. penicillin)
Staphylococcus
Penicillium
Zone of inhibited growth
Figure 31.26