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Chapter 21 Fungi What are Fungi? • The way in which Fungi grow from the ground once led scientists to classify them as nonphotosynthetic plants • However, they are not plants at all, fungi are very different • Fungi are eukaryotic heterotrophs that have cell walls Chitin • A complex carbohydrate that makes up the cell walls of fungi Fungi Nutrition • Remember that heterotrophs depend on other organisms for food • Unlike animals, fungi do not ingest their food • Instead they digest food outside their bodies and then absorb it • Many feed by absorbing nutrients from decaying matter in the soil (decomposers) • Others live as parasites, absorbing nutrients from their hosts Structure and Function of Fungi • All fungi are multicellular with the exception of yeast • Multicellular fungi are composed of thin filaments called hyphae Structure and Function of Fungi Fungus Structure • The bodies of multicellular fungi are composed of many hyphae tangled together into a thick mass called a mycelium Fungus Structure Fruiting body • The reproductive structure growing from the mycelium in the soil that you recognize as a mushroom Fungi reproduction • Most fungi reproduce both asexually and sexually Spore • A reproductive cell that is capable of growing into a new organism by mitosis alone • This is how fungi spread Fungal spore Fungi reproduction • Sexual reproduction involves two different mating types (+ and -) • When two hyphae of opposite mating types meet, their nuclei fuse together Types of fungi zygomycetes Sac Fungi Yeast Club Fungi Imperfect fungi Ecology of Fungi • Fungi have been around since life first moved onto land • Paleontologists think that fungi helped early plants to obtain nutrients from the ground • Their early appearance suggests that fungi may have been essential to plants successful colonization of the land • Overtime, fungi have become an important part of virtually all ecosystems Edible and Inedible Mushrooms • Many types of mushrooms are considered delicious • Although wild mushrooms are edible, many are poisonous • You should never pick or eat mushrooms in the wild • Leave mushroom gathering to the experts All Fungi Are Heterotrophs • Many are saprobes • Others are parasites • Others are symbionts that live in close and mutually beneficial association with other species Saprobes • Organisms that obtain food from decaying organic matter Carnivorous Fungi • Pleurotus ostreatus Fungi as Decomposers • Fungi play an essential role in maintaining equilibrium in nearly every ecosystem • They recycle nutrients by breaking down the bodies and wastes of other organisms by releasing digestive enzymes Fungi as Parasites • As useful as many fungi are others can infect both animals and plants and cause diseases • Ex.) Wheat rust, athelets foot, Candida, Cordyceps Cordyceps Symbiotic Relationships • Some fungi form symbiotic relationships in which both partners benefit Lichens • Symbiotic association between a fungus and a photosynthetic organism Lichens • The algae or cyanobacteria - Carries out photosynthesis providing the fungus with food • The fungus provides the algae or bacteria with – water and minerals that it collects and also protects the delicate algae cell • Lichens are often the first organisms to enter barren environments Mycorrhizae • Symbiotic relationship between plant roots and fungi • Fungi allow plants to – absorb more water and minerals • Fungi also release enzymes that – free nutrients into the soil • Plants provide fungi with – the products of photosynthesis
