Fungi Lecture 9b Flashcards
List the characteristics that distinguish fungi from members of other multicellular kingdoms.
Eukaryotic
• Multicellular filaments or unicellular
• Aquatic and terrestrial.
• Chemoheterotrophs that feed by absorption of other organisms.
• Non-motile.
• Cell walls that contain chitin.
• Spend most of life cycle as haploid organism.
• About 100,000 species described; estimated that about 1.5 million species exist.
Describe the major roles of fungi in ecosystems.
- Fungi are the master recyclers in terrestrial ecosystems.
• Saprophytes digest dead plant material.
• Play a key role in cycling of carbon.
• Along with a few bacteria, are the ONLY organisms capable of digesting lignin and cellulose!
• Can completely break down wood!!
• Without fungi, carbon would be trapped for a long time; terrestrial environments would be less productive - Fungi form important mutualistic relationships
• Mycorrhizal fungi
• Mycorrhizae are mutually beneficial relationships that occur between plant roots and fungi.
• Without these fungi, plant growth slows.
• Lichens
• Mutualistic relationships between fungi and either
green algae or cyanobacteria.
• Algae/cyanobacteria provided with moist environment in which to live.
• Fungi provided with carbon compounds and nitrogen (cyanobacteria)
- Mutualistic relationships with animals
- Live in guts of termites and other grazing animals
- Help to decompose wood, cellulose
- Parasitic fungi can cause economic losses and illness
• 30% of the known species of fungi make a living as parasites, mostly of plants.
• 80% of plant diseases are due to fungi.
• Rusts, smuts, mildews, wilts, and blights cause billions of dollars of crop loss annually.
• Some fungi that attack food crops produce compounds that are toxic to humans (e.g., Aflatoxins found in peanuts + grain; Ergotism from infected rye)
• Athletes foot, diaper rash, ringworm, pneumonia, and thrush are all examples of human ailments
caused by parasitic fungi. - Parasitic fungi can also have ecological impacts
• Cryphonectria parasitica
• Accidently introduced to N. America from Asia in early 1900s
• Chestnut blight epidemics killed 4 billion chestnut trees and millions of elm trees
• Radically changed the eastern US landscape
• Chestnut: Dominant tree threatened species. - Saprophytic fungi are responsible for food spoilage
• Especially in fruit and vegetables. - Penicillin anyone?
- Fungi taste good on pizza
• …and are essential to the manufacture of many other food products including bread, soy sauce, tofu, and cheese, and beverage products, including beer, wine, and whiskey.
Define “saprophyte” and explain the importance of saprophytes to terrestrial communities.
digest dead plant material.
• Play a key role in cycling of carbon.
• Along with a few bacteria, are the ONLY organisms capable of digesting lignin and cellulose!
• Can completely break down wood!!
• Without fungi, carbon would be trapped for a long time; terrestrial environments would be less productive.
Describe mycorrhizae, endophytes, and lichens and explain the role of each organism involved in these relationships.
Mycorrhizae are mutually beneficial
relationships that occur between plant roots and fungi.
• Without these fungi, plant growth slows.
trees receive large amounts of nitrogen from mycorrhizal fungi and plants transfer sugar and photosynthetic products to fungi
Endophytic fungi
• Live in aboveground parts of plants.
• Newish discovery- still much to learn
• e.g., Endophytes in some grasses produce
compounds that deter or even kill herbivores
Endophytic may improve the ability of these grasses to tolerate abiotic stresses such as drought, as well as improve their resistance to insect and mammalian herbivores, while plant gives them safe place to live
Lichens
• Mutualistic relationships between fungi and either
green algae or cyanobacteria.
• Algae/cyanobacteria provided with moist
environment in which to live.
• Fungi provided with carbon
compounds and nitrogen (cyanobacteria)
Explain the relationship between leaf cutter ants and fungi.
These insects cultivate cellulolytic fungi, in underground gardens, obvious benefit for fungi, and These insects are exclusively mycophagous, i.e., they eat fungi. The fungi that they cultivate decompose the wood and leaves brought in by the termites and ants, respectively, and provide them with digestible and nutritious mycelium.
Describe at least 3 ways in which fungi impact humans and human society
1) Rusts, smuts, mildews, wilts, and blights cause billions of dollars of crop loss annually.
• Some fungi that attack food crops produce compounds that are toxic to humans (e.g., Aflatoxins found in peanuts + grain; Ergotism from infected rye)
2) • Athletes foot, diaper rash, ringworm, pneumonia, and thrush are all examples of human ailments
3) and are essential to the manufacture of many other food products including bread, soy sauce, tofu, and cheese, and beverage products, including beer, wine, and whiskey.
Explain how fungi acquire their nutrients.
- Fungi are absorptive chemoheterotrophs
- Large molecules cannot diffuse across fungal hyphae.
- Fungi synthesize powerful hydrolytic (digestive) enzymes which they secrete outside their body, into their food.
- Perform extracellular digestion - food outside the fungus’ body is broken down into simpler compounds that the fungus can then absorb and use.
- Other fungi use enzymes to penetrate the walls of cells –> absorb nutrients from inside the cell.
Differentiate between decomposer fungi, parasitic fungi, and mutualistic fungi.
Decomposer fungi: break down and absorb nutrients from non-living organic material
Parasitic fungi: absorb nutrients from cells of living organisms
Mutualistic fungi: also absorb nutrients from host organisms, but recipicate with actions that benefit the host
Describe the basic body plan o f a fungus.
Occur in two growth forms: • Unicellular yeasts • Multicellular filamentous structures …some species adopt both growth forms. • The bodies of multicellular fungi are constructed of tiny filaments called hyphae that form an interwoven mat called a mycelium.
Describe coenocytic fungi.
Fungi that lack septa are called coenocytic
fungi.
• Consist of a continuous cytoplasmic mass with hundreds or thousands of nuclei.
Explain how the filamentous nature of the mycelium contributes to fungus feeding , and explain one downside of this structure.
The filamentous structure of the mycelium provides an extensive surface area, making absorptive feeding very efficient.
• Just one cm3 of rich organic soil may contain 1 km of fungal hyphae with a surface area of 300cm2
What might be the downside to this high surface-area to volume ratio?
• Fungi are prone to drying out - the amount of water that evaporates from an organism is a function of its SA:volume ratio.
Explain 2 specializations of hyphae that accommodate different approaches to feeding.
- Haustoria
- parasitic and mutualistic fungi
- can penetrate the tissues of their hosts to extract and/or exchange nutrients.
• Other fungi have hyphae
adapted for preying on animals
• Arthoboytrys has hyphae that are modified as hoops.
• Can constrict around a worm in less than a second!
Describe the processes of plasmogamy and karyogamy in fungi.
Plasmogamy- two hyphae of different mating types fuse; unties cytoplasm but not nuclei
Karyogamy- pairs of haploid nuclei fuse forming a diploid zygote
Explain the heterokaryotic (or dikaryotic) stage in fungal life cycles.
Heterokayotic mycelium- contains two or more distinct haploid nuclei per cell (n+n)
Explain the significance of “mating types” in fungi reproduction.
classification
