FungiChapter 19

Señora Ettinger

Answer these questions:

• How do fungi differ from other organisms?

• How does the lifestyle of a fungus enable it to obtain food?

• What factors make each phylum of fungi distinctive?

• How do fungi affect humans?

Look at page 406 of your textbook

• What do you see in the main picture on this page?

• Read the caption. What is really shown in the picture?

• Are “fungus flowers” made of fungus?

• Why would a fungus go to all the trouble of making a plant imitate a flower?

Page 406 continued

• Do you think this fungus hurts or helps the rock cress plant?

• Would you guess that fungi could flower on its own?

Characteristics of Fungi

• Cell structure

• Lifestyle

• Food acquisition

• Habitat

• Cell walls

Fungi—plants?

• Cell wall

• Mitosis

• Chlorophyll

• Dikaryon stage

Other characteristics of Fungi

• Heterotrophs

• Digest food outside its body by secreted enzymes then absorb the nutrients

• Typically terrestrial

• Key decomposers of plant material

• Most derive their nutrition from plants

• Cell walls made of chitin

Fungal Niches• Saprobes-

• Parasites-

• Symbiotic

Mutuals

Fungi Structures, page 408, draw and label figure 19-2 here:

Hyphae structure, draw Figure 19-3, page 408 here:

Hyphae• The dominant structure of fungi

• Long, multinucleated, typically multicelled, one-cell thick fungal tissue

• Typically hidden from sight since fungi grow their hyphae into their food

• Serve as vascular channels along which nutrients are passed

Mycelium• What is it?

Septa• What is it?

Septate

coenocytic

“Recess”Read Armillaria ostoyae

Part 2:

• Reproduction

• Fungal Divisions

Reproduction• All nuclei are haploid except for zygote

nuclei (except some Chytridiomycota)

• In the sexual reproduction, hyphae of two different mating strains meet and fuse but the two types of nuclei may coexist without fusion for most of the life of the fungus

• Fungi reproduce by relasin spores

Reproduction• Monokaryotic compartment has a

single nucleus

• Dikaryotic compartment has two genetically distinct nuclei– Heterokaryotic hyphae have two

kinds of genetically different nuclei

– Homokaryotic hyphae have genetically similar nuclei

Reproductive Structures

• Sporangia:

• Gametangia:

• Conidia

Fungal Divisions

• Plant-like, this groupings are called divisions instead of phyla

• Presently differentiated from slime molds and water molds

Chytridiomycota

Fungal Divisions

• Chytridiomycota• Zygomycota• Ascomycota• Basidiomycota• Deuteromycota (Fungi imperfecti) Your

book doesn’t mention this one.

Chytridiomycota

Chytridiomycota

Read

• Modern Genetics Versus Ancient Frog-Killing Fungus.

• Write a synopsis in the space provided.

• Be ready to answer questions

Chytridiomycota

Zygomycota

Zygomycota: What does the name imply?

• What does the name imply?

Zygomycota some characteristics

Zygomycota• Non-reproductive hyphae lack

septa

• Include the common bread molds

• Produce zygospores

Life Cycle and Sexual Reproduction

• Sexual reproduction is via fusion of multinucleate gametangia

• May occur between same or different mating types

• Massive, haploid zygospore forms around diploid zygote nuclei

• Meisois occurs during germination

Asexual Reproduction

• Haploid spores are produced within sporangia

• Sporangium forms at the tip of erect hypha, with separating septum

• Spores shed above substrate, dispersed by wind

ChytridiomycotaAscomycota

Ascomycota• Beneficial

• Harmful forms

Yeast

Mold

Morels

True Morel False Morel

Truffles

Truffles

Cup Fungi

Chestnut Blight

Chestnut Blight

Dutch Elm Disease

Ascomycota• Has a characteristic reproductive

structure called an ascus.

• A diploid zygote forms within ascus.

• Asci form on ascocarp of densely interwoven hyphae

Sexual Reproduction• Ascogonia are female, have trichogyne

• Antheridia are male, fuse with trichogyne

• Male nuclei travel to ascogonium to pair with opposite nuclei

• Heterokaryotic hyphae arise from point of fusion

• An ascus containing two nuclei forms at the hyphal tip

Sexual Reproduction• Nuclei within the ascus fuse, forming

diploid zygote which immediately undergoes meiosis

• Four haploid daughter nuclei are the result.

• These haploid daughter nuclei undergo mitosis to form 8 ascospores

• The ascospores are then released, in most cases by the ascus bursting.

Asexual Reproduction• Conidia are produced at the ends

of conidiophores. Conidiophores are the stalk-like vertical growths on the hyphae. Spores are formed at the end of the conidiophores and are separated by septum and are called conidia.

• The spores are released and then germinate

Chytridiomycota

Basidiomycota

Basidiomycota• Includes mushrooms, jelly fungi,

puffballs, rusts and smuts

• Includes edible as well as poisonous varieties

Mushrooms

Mushrooms

Mushrooms

Jelly Fungus

Jelly Fungus

Puffballs

Rusts

Rusts

Corn Smut

Basidiomycota

• Characteristic reproductive structure is called a basidium.

• Syngamy occurs within basidium

• Meiosis occurs immediately, forming four haploid basidiospores

• Four basidiospores are borne on one basidium

Sexual Reproduction• Spore germinates forming homokaryotic

hyphae• Eventually septa form between nuclei of

primary mycelium• Dikaryotic, heterokaryotic secondary

mycelium forms when hyphae of different mating types fuse

• Basidiocarps form of completely dikaryotic hyphae

• Basidia line the gills of typical mushrooms

Deuteromycota• Commonly called Fungi Imperfecti

because they exhibit only asexual reproduction

• Mostly ascomycetes, few zygomycetes and basidiomycetes

• Many are human and plant pathogens• Others produce important chemicals

such as penicillin

Parasexuality• Parasexuality occurs when two

different hyphae fuse forming heterokaryotic hyphae. The two different nuclei may exchange portions of chromosomes between nuclei.

• Provides a certain amount of genetic recombination.

Fungal Associations

• Lichens

• Mycorrhizae

Lichens• Mostly ascomycetes with green algae

and/or cyanobacterium• Specialized hyphae penetrate or

envelop photosynthetic cells• Fungal chemical signals direct

photosynthetic metabolism• Could be considered a form of

controlled parasitism

Lichens• Reproduction of the fungal portion is

via normal fungal sexual reproduction

• Reproduction of the photosynthetic component is asexual

• The lichen as a whole can fragment and be transported by wind… to a new location to form a new individual

Lichens• Can inhabit cold, dry, generally harsh

environments• Help break rock surfaces and prepare

habitat for other organisms• Coloration of lichen protects

photosynthetic partner• Can survive adverse conditions by

nearly halting metabolism

Mycorrhizae• Most plant roots associated with

certain fungi

• Fungus aid in transfer of soil nutrients into roots

• Plant provides organic carbon to fungus

• Arbuscular mycorrhizae and ectomycorrhizae

Arbuscular Mycorrhizae• Hyphae penetrate outer cells of root

• More common mycorrhizae, generally a zygomycetes

• May increase yield of crops with less energy input

Ectomycorrhizae• Hyphae surround, but do not

penetrate roots

• Less common, mostly basidiomycetes, some ascomycetes

• Characteristic symbiont of shrubs and trees

Advantages• Plants more resistant to drought, cold

and harsh conditions

• May provide better protection against acid precipitation

• Prevent accumulation of toxic metals

• Speed germination of orchid seeds

• Provide better growth in poor soils