Chapter 31 – Introduction to Fungi

Fungi characteristics • Heterotrophic

• External digestion

• Hyphae– Threadlike filaments– Chains of cells can be

separated by cross walls • pores

– Some fungi lack cross walls, and have many nuclei within large mass of cytoplasm

Fungal structure

• Hyphae branch repeatedly to form mycelia

• Mushroom

• Fast growth – Longer but not

thicker

Fungal life cycle• Many species can

reproduce sexually and asexually

• Haploid spores transported by water or wind

• Sexual reproduction – 2 haploid mycelia of

different mating types grow towards each other and fuse

• Heterokaryotic (n + n)

Fungal life cycle cont

• Asexual reproduction – Mold

• Produce spores on tips of specialized hyphae

– Yeast • Budding

Fungal groups

• Sexual reproductive structures often used to classify– Imperfect fungi – no

known sexual stage

• All but one group lack flagella – Evolved from

flagellated ancestor

Fungal groups cont

• Chytrids • Zygomycetes or zygote fungus • Glomeromycetes • Ascomycetes or sac fungus • Basidiomycetes or club fungus

Chytrids

• Only fungi with flagellated spores

• Earliest line of fungi

• Lakes, ponds, soil

• Decomposers or parasitic

Zygomycetes • Fast growing molds

• Asexual reproduction when food is abundant; sexual when scarce

• Zygosporangium formed from fused mycelia – Tolerate dry/harsh

environment

Glomeromycetes

• Form distinct type of mycorrhizae

– Symbiotic relationship with plant roots

– Invade plant root and branch into treelike structures (arbuscles)

Ascomycetes

• Saclike structures called asci produce spores – Sexual reproduction when

harsh environment

• Unicellular yeast, morels, cup fungus

• Lichen – Symbiotic relationship with

cyanobacteria or algae

Basidiomycetes

• Mushrooms, puffballs, shelf fungus / plant parasites rusts and smuts

• Club shaped, spore producing structure called basidium

Parasitic fungi

• Corn smut

• Ergot

• Mycosis – Mild to systemic – Opportunistic

Benefits of fungi • Mutualistic symbiotic relationships

• Essential decomposers – Organic matter, petroleum products, toxic chemicals

• Food products

• Medicinal value– Antibiotics (penicillin the first)

• Laboratory work