7. Chapter 31: Fungi Flashcards
What is the main function of fungi?
decompose organic material
What are the similarities and differences between plant and fungi?
Similar: eukaryotes and most are multicellular Differences: nutritional mode (heterotrophs by nutrient absorption), cell walls, growth, and reproduction
What are exoenzymes?
Secreted by the fungus, digest food outside its body to simpler compounds
How are fungi constructed?
tiny filaments that form an interwoven mat (Hyphae: tiny filaments that form the body of most fungi, Mycelium: a densely branched network of hyphae in a fungus)
Do fungal hyphae have cell walls?
Yes, these are built mainly of chitin – a strong but flexible polysaccharides. (Chitin is also found in the exoskeleton of arthropod)
What is the function of septa?
divides the multicellular fungi with hyphae into cells. (generally have large pores)
What do fungi that lack septa consist of?
continuous cytoplasmic mass with hundreds of nuclei (can have repeated nuclear division without cytoplasmic division)
What are haustoria?
some modified hyphae in parasitic fungi; nutrient-absorbing tips that penetrate the tissue of their host (some adapted to preying on animals)
How do fungi reproduce?
By releasing spores
How many fungi species are known? How many species estimated worldwide?
More than 100, 000 species of fungi are known; 1.5 million species worldwide.
What are the four phyla of fungi?
Zygomycota, Ascomycota, Basidiomycota
(We don’t use the term of male or female here, we only use positive or negative (they are not genetically identical) In heterokaryotic stage = zygosporangium Karyogamy => 2N nuclei)
- Asexual reproduction
- sexual reproduction
- mycelium
- spore-producing structures
- spores
- germination
- plasmogamy (fusion of cytoplasm)
- Heterokaryotic stage
- karyogamy (fusion of nuclei)
- zygote
- meiosis
What is the ploidy of the nuclei of fungal hyphae and spores of most species?
Haploid
What is the process in which the cytoplasm of two genetically different hyphae fuse?
Plasmogamy (results in the formation of a heterokaryon)
What is a heterokaryon?
a mycelium with two genetically distinct nuclei
What is Karyogamy?
fusion of the haploid nuclei contributed by the two parents, occurs after the fusion of the cytoplasm
The life cycle and biology of Rhizopus stolonifer, black bread mold, is typical of zygomycetes.
First a spore must reach the bread; they are almost everywhere. Hyphae spread out over food and digest nutrients. In the asexual phase, hundreds of haploid spores develop in sporangia. If environmental conditions deteriorate, they reproduce sexually. Plasmogamy (fusion of cytoplasm) of opposite mating types produces a resistant structure, the zygosporangium. In the zygosporangium, the multiple haploid nuclei undergo Karyogamy, the fusion of the haploid nuclei contributed by the two parents. These diploid nuclei undergo meiosis, producing haploid spores. Note: there is no multicellular diploid stage.
What is phylum ascomycota also known as? Where do half of the species live?
sac fungi (range in size and complexity from unicellular yeasts to elaborate cup fungi and morels) About half the ascomycete species live with algae in mutualistic associations called lichens.
What is the defining feature of ascomycota?
the formation of an ascus, a sac containing eight spores formed during sexual reproduction.
Where is the name of the phylum Basidiomycota derived?
the basidium, a reproductive appendage that produces sexual spores. (The club like shape of the basidium is responsible for the common name, club fungus.)
How many know species of fungi are in phylum Basidiomycota? List some examples.
Approximately 25,000 fungi, including mushrooms, shelf fungi, and puffballs
What is a mold?
rapidly growing, asexually reproducing fungus. (the same fungus may reproduce sexually, producing zygosporangia, ascocarps, or basidiocarps)
Why can’t some molds be classified as zygomycetes, ascomycetes, or basidiomycetes?
because they have no known sexual stages (imperfect fungi)
What are yeast? How do they reproduce?
unicellular fungi that inhabit liquid or moist habitats, including plant sap and animal tissues. asexually by simple cell division or budding off a parent cell. (Some yeast reproduce sexually, forming asci or basidia, but others have no known sexual stage)
What are lichens?
a mutualistic symbiosis of millions of photosynthetic microorganisms held in a mesh of fungal hyphae. (The fungal component is commonly an ascomycete. The photosynthetic partners are usually green algae)
What are mycorrhizae?
mutualistic associations of plant roots and fungi. (Extensions increases the absorptive surface of the plant roots; Fungus accesses some minerals from the soil, and the plant provides organic nutrients; Almost all vascular plants have it; some plants that grow in nitrogen poor soil rely on their fungal symbionts to fix N2.)
Draw the zygomycota life cycle.
