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How do fungi acquire nutrients from their environment?
- Fungi are heterotrophs and absorb nutrients from outside of their body
- Fungi use enzymes to break down a large variety of complex molecules into smaller organic compounds
- The versatility of these enzymes contributes to fungi's ecological success
- Fungi exhibit diverse lifestyles-decomposers, parasites, mutualists
- The morphology of mulitcellular fungi enhances their ability to abosrb nutrients
- Fungi consist of mycelia, networks of branched hypae adapted for absorption
- Most fungi have cell walls made of chitin
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Describe and compare the sexual and asexual life cycles of fungi
- Fungi propagate themselves by producing vast numbers of spores, either sexually or asexually
- Fungi can produce spores from different types of life cycles
- Fungal nuclei are normally haploid, with the exception of transient diploid stages formed during the sexual life cycles
- Sexual reproduction requires the fusion of hyphae from different mating types
- Fungi use sexual signaling molecules called pheromones to communicate their mating type
- In addition to sexual reproduction, many fungi can reproduce asexually
- Molds produce haploid spores by mitosis and form visible mycelia
- Instead of producing spores, yeasts reproduce asexually by simple cell division and the pinching of "bud cells" from a parent cell
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What is the role of a mushroom?
- The life cycle of a basidiomycete usually includes a long-lived dikaryotic mycelium
- In response to environmental stimuli, the mycelium reproduces sexually by producing elaborate fruiting bodies called basidiocarps
- Mushrooms are examples of basidiocarps
- The numerous basidia in a basidiocarp are sources of sexual spores called basidiospores
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Describe the structure and characteristics of lichens.What sort of relationships do they embody?
- A lichen is a symbiotic association between a photsynthetic microorganism and a fungus in which millions of photsynthetic cells are held in a mass of fungal hyphae
- The fungal component of a lichen is most often an ascomycete
- Algae or cyanobacteria occupy an inner layer below the lichen surface
- The algae provide carbon compounds, cyanobacteria provide organic nitrogen, and fungi provide the environment for growth
- The fungi of lichens can reproduce sexually and asexually
- Asexual reproduction is by fragmentation or the formation of soredia, small clusters of hyphae with embedded algae
- Lichens are important pioneers on new rock and soil surfaces
- Lichens are sensitive to pollution, and their death can be a warning that air quality is deteriorating
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Describe some positive ecological and practical roles of fungi
- Humans eat many fungi and use others to make cheeses, alcoholic beverages, and bread
- Some fungi are used to produce antibiotics for the treatment of bacterial infections, for example the ascomycete Penicillium
- Genetic research on fungi is leading to applications in biotechnolgy
- For examples, insulin-like growth factor that can be produced in the fingus Saccharomyces cerevisiae
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Describe mycorrhizae and the role they may have played in plant evolution
- Mycorrhizae are mutually beneficial relationships between fungi and plant roots
- Ectomycorrhizal fungi from sheaths of hyphae over a root and also grow into the extracellular spaces of the root cortex
- Arbuscular mycorrhizal fungi extend hyphae through the cell walls of root cells and into tubes formed by invagination of the root cell membrane
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Describe plasmogamy, karyogamy, and the heterokaryotic stage in a mushrooms life cycle
- Plasmogamy is the union of two parent mycelia
- In most fungi, the haploid nuclei from each parent do not fuse right away; they coexist in the mycelium, called a heterokaryon
- In some fungi, the haploid nuclei pair off two to a cell; such a mycelium is said to be dikaryotic
- Hours, days, or even centuries may pass before the occurence of karyogamy, nuclear fusion
- During karyogamy, the haploid nuclei fuse, producing diploid cells
- The diploid phase is short-lived and undergoes meiosis, producing haploid spores
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