Mader: Biology 8th Ed.

The Fungi

Chapter 23

Mader: Biology 8th Ed.

Outline• Characteristics• Structure• Reproduction• Evolution• Sac Fungi• Yeasts• Club Fungi• Smuts and Rusts• Imperfect Fungi• Symbiotic Relationships

Mader: Biology 8th Ed.

Characteristics of the Fungi

• Kingdom Fungi contains the fungi.– Mostly multicellular eukaryotes that share

a common mode of nutrition.HeterotrophicCells release digestive enzymes and

then absorb resultant nutrient molecules.

Some are parasitic.Several have mutualistic relationship.

Mader: Biology 8th Ed.

Structure of Fungi

• Yeasts are best known example of unicellular fungi.– Body (thallus) of most fungi is multicellular

mycelium.Network of hyphae give the mycelium a

large surface area per unit volume.

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Mycelium of Fungi

Mader: Biology 8th Ed.

Structure of Fungi

• Fungal cells are quite different from plant cells.– Lack chloroplasts and have a cell wall

containing chitin and not cellulose.– Energy reserve is glycogen, not starch.

• Nonmotile– Septate fungi have cross walls in their

hyphae.– Nonseptate fungi are multinucleated.

Mader: Biology 8th Ed.

Reproduction of Fungi

• Both sexual and asexual reproduction occur.

• Fungal sexual reproduction involves three stages:– Haploid Hyphae– Dikaryotic Stage– Diploid Zygote

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Reproduction of Fungi

• During sexual reproduction, hyphae from two different mating types fuse.– Hyphae that contains paired haploid

nuclei is said to be dikaryotic.– Fungal spores germinate directly into

haploid hyphae without embryological development.

• Asexual reproduction usually involves the production of spores.– Unicellular yeasts reproduce by budding.

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Evolution of Fungi

• Has been suggested fungi evolved from red algae because both fungi and red algae lack flagella in all stages of the life cycle.– Zygospore Fungi

(phylum Zygomycota) are mainly saprotrophs living off animal and plant remains.

Produce spores with sporangia. Name refers to the zygospore seen

during sexual reproduction.

Mader: Biology 8th Ed.

Sac Fungi• Most sac fungi (phylum Ascomycota) are

saprotrophs that digest resistant materials containing cellulose, lignin, or collagen.– Most are composed of septate hyphae.– Ascus refers to the fingerlike sac that

develops during sexual reproduction.Asci usually surrounded and protected

by sterile hyphae within an asocarp.– Asexual reproduction involves production

of conidiospores.

Mader: Biology 8th Ed.

Yeasts

• Term yeasts is generally applied to unicellular fungi.– Many are ascomycetes.– Budding is common form of asexual

reproduction.– Sexual reproduction results in the

formation of asci and ascospores.– When some yeast ferment, they produce

ethanol and carbon dioxide.

Mader: Biology 8th Ed.

Yeast Cells

Mader: Biology 8th Ed.

Club Fungi

• Club fungi (phylum Basidomycota) include mushrooms and bracket fungi.– These are fruiting bodies called

basidiocarps.Contain basidia, club-shaped structures

that produce basidiospores.– Usually reproduce sexually.

Mader: Biology 8th Ed.

Club Fungi

Mader: Biology 8th Ed.

Smuts and Rusts

• Smuts and rusts are club fungi that parasitize cereal crops.– Great economic importance because of

annual crop losses.Do not form basidiocarps.Life cycle often requires two different

plant hosts to complete the cycle.

Mader: Biology 8th Ed.

Smuts and Rusts

Mader: Biology 8th Ed.

Imperfect Fungi

• Imperfect fungi (phylum Deuteromycota) always reproduce asexually by forming conidiospores.– Produced at tips of modified aerial

hyphae.– Known as imperfect in the sense that a

sexual stage has not yet been observed.Penicillium - PenicillinAspergillus - Soy sauceCandida albicans- Yeast infections

Mader: Biology 8th Ed.

Penicillium

Mader: Biology 8th Ed.

Symbiotic Relationships

• Lichens– Association between a fungus and a

cyanobacterium or green alga.Specialized fungal hyphae penetrate

photosynthetic cells and transfer nutrients directly to the fungus.

Can live in areas of extreme conditions and contribute to soil formation.

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Lichen Morphology

Mader: Biology 8th Ed.

Mycorrhizas

• Mycorrhizas are mutualistic relationships between soil fungi and the roots of most plants.– Help plants acquire mineral nutrients.

Give plant greater absorptive surface.

Mader: Biology 8th Ed.

Review• Characteristics• Structure• Reproduction• Evolution• Sac Fungi• Yeasts• Club Fungi• Smuts and Rusts• Imperfect Fungi• Symbiotic Relationships

Mader: Biology 8th Ed.