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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