rav65819_ch31_603-620

rav65819_ch31_603-620 - ; 31 chapter Fungi introduction THE...

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;;;;;;;; 31 chapter Fungi introduction
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THE FUNGI, AN OFTEN-OVERLOOKED group of unicellular and multicellular organisms, have a profound influence on ecology and human health. Along with bacteria, they are important decomposers and disease-causing organisms. Fungi are found everywhere—from the tropics to the tundra and in both terrestrial and aquatic environments. Fungi made it possible for plants to colonize land by associating with rootless stems and aiding in the uptake of nutrients and water. Mushrooms and toadstools are the multicellular spore-producing part of fungi that grow rapidly under proper conditions. A single Armillaria fungus can cover 15 hectares underground and weigh 100 tons. Some puffball fungi are almost a meter in diameter and may contain 7 trillion spores—enough to circle the Earth’s equator! Yeasts are used to make bread and beer, but other fungi cause disease in plants and animals. These fungal killers are particularly problematic because fungi are animals’ closest relatives. Drugs that can kill fungi often have toxic effects on animals, including humans. In this chapter we present the major groups of this intriguing life form. concept outline 31.1 De±ning Fungi 31.2 General Biology of the Fungi The body of a fungus is a mass of connected hyphae Fungal cells may have more than one nucleus Mitosis divides the nucleus, not the hypha Fungi can reproduce both sexually and asexually Fungi are heterotrophs that absorb nutrients 31.3 Phylogenetic Relationships New fungal phylogenies are emerging Not all groups are monophyletic 31.4 Chytridiomycetes: Aquatic Fungi with Flagellated Zoospores 31.5 Zygomycetes: Fungi That Produce Zygotes In sexual reproduction, zygotes form inside a zygosporangium Asexual reproduction is more common 31.6 Glomeromycetes: Asexual Plant Symbionts 31.7 Ascomycetes: The Sac (Ascus) Fungi Sexual reproduction occurs within the ascus Asexual reproduction occurs within conidiophores Some ascomycetes have yeast morphology Ascomycete genetics and genomics have practical applications 31.8 Basidiomycetes: The Club (Basidium) Fungi
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Basiciomycetes sexually reproduce within basidia The secondary mycelium of basidiomycetes is heterokaryotic 31.9 Deuteromycetes: A Polyphyletic Group That Includes Most Molds Deuteromycetes have limited genetic recombination Deuteromyctes include economically important genera 31.10 Ecology of Fungi Fungi have a range of symbioses Endophytes live inside plants and may protect plants from parasites Lichens are an example of symbiosis between different kingdoms Mycorrhizae are fungi associated with roots of plants Fungi also form mutual symbioses with animals 30.11 Fungal Parasites and Pathogens Fungal infestation can harm plants and those who eat them Fungal infections are dif±cult to treat in humans and other animals 603 rav65819_ch31_603-620.indd 603 rav65819_ch31_603-620.indd 603 12/7/06
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rav65819_ch31_603-620 - ; 31 chapter Fungi introduction THE...

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