FUNGI Chapter 31. The Little Known Fungi 100,000 species known, 1.5 million unknown (estimate) ...
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Transcript of FUNGI Chapter 31. The Little Known Fungi 100,000 species known, 1.5 million unknown (estimate) ...
The Little Known Fungi
100,000 species known, 1.5 million unknown (estimate)
Some are single-celled (yeast), but most multicelled (mushrooms)
Found in every habitat Diverse, widespread, and essential for well-being Formerly classified as plants
Molecular data says more closely related to animals Mycologists are the scientists that study fungi
Nutrition
Heterotrophs, but absorb food instead of digest Secrete enzymes into environment to break
complex molecules into something more manageable
Enzymes also disrupt walls of plant cells for nourishment
Live as decomposers, parasites, or mutualisms' Fit into multiple niches Can digest wide range of food sources
Body Structure
Most grow as filaments and yeasts Yeast only growth is rare
Bodies form filamentous networks called hyphae Form a mycelium to
increase SA/volume ratio Proteins synthesized to
rapidly extend (not grow) hyphae Concentratie of energy
and resources to accomplish
Not motile, but can move hyphae
Specialized Hyphae
Some allow predation of living animals
Haustoria allow nutrient extraction or exchange
Mycorrhizae are mutually beneficial relationships between fungi and plants Improve mineral delivery to
plants in exchange for carbs
Ectomycorrhizal fungi: form a sheath of hyphae over plant roots and between plant cells
Arbuscular mycorrhizal fungi: extend hyphae through root cell walls and into plant
Sexual Reproduction
Hyphae release pheromones
Different mating types attract
Heterokaryon, nuclei don’t fuse right away
Dikaryotic, nuclei pair off and divide without fusing
Time to karyogamy varies
Usually only 2n stage
Final steps generate genetic variation
Asexual Reproduction
Varies widely among fungi (like sexual)
Produce haploid spores by mitosis Informally known as
molds if mycelia is visible
Grow rapidly and reproduce sexually if contacted by species of different mating type
Yeasts produce budding cells or spores via mitosis
Deuteromycetes reproduce asexually only
5 phyla recognized currently, but chytrids are likely paraphyletic
Study cycle diagrams for reproductive differences
Fungi Functional Groups
Chytridium globular fruiting bodies, one of the earliest to diverge
Mucor, grow into fruits and breads;may act as decomposers, parasites,or symbionts
Ecologically important; form mycorrhizal associations with plants
Sac fungi, common to water and land Aleuria aurantia
Decomposers and ectomycorrhizal fungi; fruiting bodies commonly called mushrooms
Phylum Chytridiomycota
Called chytrids and found in lakes and soil
Decomposers and pararsites of protists, other fungi, plants, or animals Live in sheep GI tracts to
help process plants Some form colonies with
hyphae, others as single cells
Only phyla with flagellated spores called zoospores
Phylum Zygomycetes
Reproduce by zygospores Sexually, formed in
zygosporagium Asexually, formed
atop sporangiophores Rhizopus stolonifer is
black bread mold Know the life cycle
Philobolus ‘aim’ and shoot sporangium
Resistant to freezing and drying
Phylum Glomeromycetes
Form arbuscular mycorrhizae Tips of hyphae push
into plant root cells and branch into treelike structures
Minerals to plant and organic compounds to fungi
Mutualistic partnership with 90% of all plant species
Phylum Ascomycetes
Reproduce sexually by spores in asci (sacs) and bear stages in ascocarps (fruiting bodies)
Reproduce asexually by conidiospores, spores formed at tips of hyphae called conidiophores
Include: morels and truffles Yeasts used in beer industry
Phylum Basidiomycetes
Includes mutualists that form mycorrhizae and plant parasites
Reproduce sexually by producing fruiting bodies called basidiocarps Produces 4 haploid
nuclei Asexual reproduction
is rare
Decomposers
Any carbon containing substance can be consumed by some fungi
Important use in bioremediation Maintain essential inorganic nutrients for
plant growth Return nutrients to the soil
Mutualists
Fungus-Plant Ascomycetes benefit by producing toxins to deter
prey Fungus-Animal
Decomposers convert otherwise indigestible plant material
Lichens: symbiotic association with algae Algae contribute carbon compounds and fix nitrogen Fungi contribute suitable environments for growth Reproduce separately
Lichen: asexually via soredia, clusters of hyphae with algae
Pathogens Mostly on or in plants
Ascomycete Cryphonectria parasitica attacks chestnuts Basidiomycete Puccinia graminis causes black stem rust
on wheat Ascomycete Aspergillus contaminates improperly stored
grains and peanuts by secreting carcinogenic aflatoxins Mycosis are those that parasitize humans
Ascomycetes cause ringworm and athlete’s foot Coccidioidomycosis produces tuberculosis like
symptoms in lungs Candida albicans normal on moist epithelia, grow to
rapidly causes vaginal infections, diaper rash, and thrush