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AP Biology, Chapter 31Fungi

SummaryIntroduction

INTRODUCTION TO THE FUNGIIntroduction1. List the characteristics that distinguish fungi from organisms in the other fourkingdoms.

a. Nutritional modei. Heterotrophsii. Absorption after extracellular digestion

b. Structural organizationi. Many filamentous hyphae make up a myceliumii. Nuclei may be separated by septaiii. Hyphae may be modified as haustoria for parasitism

c. Growth: mainly by elongation of hyphaed. Reproduction

i. Asexual by spores or fragmentationii. Sexual by hyphal, followed by nuclear fusion

Absorptive nutrition enables fungi to live as decomposers and symbionts2. Explain how fungi acquire their nutrients.

a. Secrete exoenzymes for extracellular digestionb. Gain nutrients by absorptionc. Roles: decomposers, parasites, mutualists

Extensive surface area and rapid growth adapt fungi for absorptivenutrition

3. Explain how non-motile fungi seek new food sources and how they disperse.a. Motile: spores and unicellular forms spread by wind, water, animalsb. Non-motile

i. Hyphae grow chemotaticallyii. Fragments can be spread passively

4. Describe the basic body plan of a fungus.a. Non-clade body plans: yeast, mold, lichen, mycorrhizaeb. Most common form

i. Hyphae, branched to form a myceliumii. Tubes of cytoplasm with chitin cell walls and eukaryotic partsiii. May or may not (coenocytic) be divided into cells by septaiv. Haustoria have tips adapted for penetration

c. Adaptationsi. Many thin hyphae provide surface area for absorptionii. Each hypha can extend and branch to exploit a new resource

Fungi reproduce by releasing spores that are produced either sexually orasexually

5. Describe the processes of plasmogamy and karyogamy.

a. Plasmogamyi. Fusion of cytoplasmsii. Dikaryotic (heterokaryotic) hyphae contain two types of haploid

nucleib. Karyogamy

i. Fusion of nucleiii. Pairs of nuclei in dikaryotic hyphae may fuseiii. Meiosis may then produce haploid spores


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DIVERSITY OF FUNGIIntroduction

6a. What defines the clade including all fungi?a. Protein and nucleic acid sequence data

6. Distinguish among the groups Chytridiomycota, Zygomycota, Ascomycota,

and Basidiomycota. Include a description of the sexual structure that characterizeseach

group and list some common examples of each.Division Chrytidiomycota: Chrytids may provide clues about fungal origins

a. General descriptioni. Coenocytic hyphae with chitin cell wallsii. Mainly aquatic saprobes and parasites

b. Sexual structurei. Only fungus with a flagellated zoosporeii. Evolutionary link between fungi and a flagellated protist

Division Zygomycota: Zygote fungi form resistant dikaryotic structuresduring sexual

reproductiona. General description

i. Coenocytic hyphaeii. Saprophytic and mutualistic as mycorrhizae

b. Sexual structurei. Resistant, dark zygosporangia form at the site of hyphal

fusion

ii. Under favorable conditions: karyogamymeiosissporeformation

iii. See diagram of characteristic sexual structure in textc. Common examples

i. Black bread mold, Rhizopusii. Cow dung "shotgun" fungus, Pilobolus

Division Ascomycota: Sac fungi produce sexual spores in saclike ascia. General description

i. Sac fungiii. Hyphae with septaiii. Marine, freshwater and terrestrial

b. Sexual structurei. Antheridium of the male hypha transfers its nuclei to

ascogonium ofthe femaleii. Ascogonium develops into mushroom-like ascocarpiii. Karyogamy occurs in hyphal tipsiv. Meiosis produces haploid spores in saclike asciv. See diagram of characteristic sexual structure in text

c. Common examples

i. About half are in lichensii. Morels are mycorrhizaeiii. Truffles cost $600/lb.iv. Saccharomyces ferments bread and winev. Rice blast fungusvi. Candida

Division Bascidiomycota: Club fungi have long-lived dikaryotic mycelia anda

transient diploid stage


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a. General descriptioni. Club fungi: mushrooms, shelf fungus, puffballs, rusts and

smutsii. Saprophytes, mycorrhizae, parasitesiii. Especially adept at digesting wood

b. Sexual structure

i. Meiosis takes place in diploid, club-shaped basidia under themushroom capii. Haploid spores bud from the ends of the basidiaiii. Entire fruiting structure = basidiocarpiv. See diagram of characteristic sexual structure in text

c. Common examplesi. Many edible forms and poisonous toadstools andAmanitaii. Stinkhornsiii. Rhodotorula, pink shower curtain yeast

Molds, yeasts, lichens, and mycorrhizae represent unique lifestyles thatevolved

independently in three fungal divisions7. Compare the structures and life cycles of molds, yeasts, lichens, and

mycorrhizae.a. Molds

i. Common name for mycelial formsii. Fingi Imperfecti

.Old non-clade name Deutromycota

.No sexual stage; incl. carnivores and Penicilliumb. Yeasts

i. Unicellular forms; some also have hyphal formsii. Some reproduce by buddingiii. Saccharomyces, Rhodotorula, Candida

c. Lichensi. Mutualistic fungi and algaeii. Fungi provide structure and protectioniii. Algae provide autotrophy and nitrogen fixationiv. Can co-reproduce asexually by sorediav. Important pioneer species; dissolves rock, makes soilvi. Indicator species of air pollution

d. Mycorrhizaei. Mutualistic roots and fungiii. 95% of plants participate

ECOLOGICAL IMPACTS OF FUNGIIntroduction

8. Describe the roles of fungi in ecosystems.a. Decomposers break up large dead organisms, release nutrientsb. Bind soil: prevent erosion and hold waterc. Diseases control population growth

Ecosystems depend on fungi as decomposers and symbiontsSome fungi are pathogens

9. Explain how fungi can be dangerous and costly to humans.a. Human diseases: athlete's foot, Candidiasis, Aspergillosis,

Pneumocystis, nailinfection, ringwormb. Poisonings: aflatoxin, ergot poisoning, toxic black moldc. Agricultural diseases: rusts, smut, rice blastd. Expensive corrosion


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Many animals, including humans, eat fungi10. Explain how fungi are commercially important.

a. Fermentation in making bread, alcoholb. Antibiotics: Penicillium makes penicillinc. Flavorings in cheesesd. Genetically engineered to make eukaryotic glycoproteins

PHYLOGENETIC RELATIONSHIPS OF FUNGIFungi and animals probably evolved from a common protistan ancestor11. Describe the evolutionary relationships between the four fungal groups.

a. Represent progressive adaptations for reproduction and dispersal onland

b. See cladogram in text12. Describe the nature of the common ancestor of fungi and animals.

a. Relationship based on molecular evidencec. Both from a flagellated protist ancestor

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