Lecture 17 Fungi Flashcards
what supergroup + subgroup are fungi in?
- Unikonts - Opisthokonts
- more closely related to animals than plants
despite their diversity, what are the key traits of fungi? (esp. re: nutrition)
- fungi are chemoheterotrophs that absorb nutreints from outside of their body
- fungi secrete enzymes (exo enzymes) to break down a large variety of complex molecules into smaller organic compounds – external digestion
- versatility of these enzymes - can digest cellulose + lignin from plants; chitin + keratin from animal tissues
- simple organic molecules absorbed by body of fungus
what are 6 body structures of fungi?
- most common: multicellular filaments and single cells
- chitin in cell wals
- mycelia
- septae (most) or coenocytic
- large SA:V – morphology good at absorbing nutrients
- grow very quckly
what are mycelia?
- branched networks of hyphae adapted for absorption
what are septae?
- fungi w/ hyphae divided into cells by septa-cross walls
- pores allow for cell-to-cell movement of organelles
what are coenocytic fungi?
- continuous cytoplasmic mass with hundreds or thousands of nuclei
what are haustoria?
specialized hyphae in unique fungi that allow to penetrate tissues of their host
what are mycorrihizae?
- mutually beneficial relationships between fungi and plant roots
- deliver PO4 ions and minerals to plants
- in most vascular plants
what are ectomycorrhizal fungi?
- fungi that form sheaths of hyphae over a root and also grow into extracellular spaces of root cortex
- don’t haustoria
what are arbuscular mycorrhizal fungi (endomycorrhizae)?
- extend hyphae through cell walls of root cells and into tubes formed by invagination of root cell membrane
how do fungi propagate themselves?
- produce a vast number of spores sexually or asexually
why is the spore of fungi different than the spore of plantae?
- made via mitosis AND meiosis (only mei in plants)
- BUT always haploid
- resistant to desiccation and act as dispersal stages
what are coenocytic hyphae usually?
homokaryotic – multiple, identical nuclei
what are fungal nuclei usually?
haploid, with the exception of transient diploid stages formed during sexual life cylces
- nuclei of hyphae and spores are haploid
what does sexual reproduction require?
fusion of hyphae form different mating types - use sexual signalling molecules called pheromones to communicate their mating type
what is plasmogamy?
the union of cytoplasm form two parent mycelia
- in most fungi, haploid nuclei don not fuse right away, coexist in mycelium called heterokaryon
what is the pairing of two haploid nuclei to a cell, such as a mycelium called?
- dikaryotic
what is karyogamy?
nuclear fusion – diploid phase
how long is the diploid phase in fungi?
short-lived, undergoes meiosis, producing haploid species
how do fungi reproduce asexually?
- molds produce haploid spores by MITOSIS and form visible mycelia
- unicellular yeasts produce asexually by simple cell division –bud cells
- some can grow as yeasts and as filamentous mycelia
- many molds and yeast have no sexual stage known
what are the five lineages of fungi?
Phylum:
- Chytridiomycota
- Zygomycota
- Ascomycota
- Glomeromycota
- Basidiomycota
what are chytridiomychota?
- found in freshwater
- diverged early in fungal evolution, prob PARAPHYLETIC
- have flagellated spores called ZOOSPORES
- cell walls - chitin, use external digestion
- decomposers, parasites, mutualists
- global decline of amphibians - eat their kerating omgalksfjsdka
what are zygomycota
- very diverse
- Rhizopus stolonifer hyphae are coenocytic
- named for zygosporangia - site of karyogamy and then meiosis
- resistant to freezing and drying, can survive unfavourable conditions
what are glomermycota?
- species forms symbiotic relationships with roots of plants
- form arbuscular mycorrhizae
what are ascomycota?
- sac-fungi
- larges phylum
- separate hyphae
- production of sexual spores in sac-like asci contained in fruiting bodies called ascocarps
- reproduce asexually by spores called conidia - not formed in sporangia - produced asexually at tips of specialized hypha called conidiophores
what are basidiomycota? (club fungi)
- mushrooms, puffballs, shelf fungi, mycorrhizae, plant parasites
- decomposers of wood
- defined by club like structure called basidium - transient diploid stage in life cycle
- long dikaryotic mycelium
- reproduces sexually by fruiting bodies called basidiocarps
what are characteristics of basidiocarps?
- have thin vertical sheets of tissue called gills that are lined with millions of basidia
what are yeasts?
- unicellular fungi that inhabit liquid/moist habitats
- asexual rep
- occasional sexual rep
- asco or basidio
what are molds?
- rapidly growing asexually reproducing fungi
- zygo, asco, basidio
what are mycorrhizae?
- mutualistic symbiosis of plant roots AND fungi
- glomero, zygo, asco, basidio all involved
what are 3 ways fungi interact with organisms
- decomposers
- mutualists
- pathogens
what do fungi do as decomposers?
- break down complex organic compounds to inorganic (mineral) forms
- bridge between living and non living world
- C + N cycling form dead tissues
- Fungi > Bacteria for cellulose & lignin decomp
- Fairy Rings - outward growth of decomposer hyphae - mushroom when cond. favourable
- release of nutrients form detritus
what do fungi do as mutualists?
- plants: mycorrhizae
- animals: digestive services ex Chytrid: guts of sheep and cattle, ants
what is a lichen?
- symbiotic association between a photosynthetic microorganism and a fungus
- fungi provide enviro for growth, alga provide carbon compounds, cyanobact provide N
- fungi of lichens can produce asexually (via soredia)/or sexually
what are soredia?
asexual reproduction mechanism of lichen fungi that are small clusters of hyphae with embedded algae
what do fungi do as pathogens?
Plants: wilt: hyphae block xylem; necroses: fungi digesting plant tissues
Invertebrates: digest chitin, parasites
contrast localized subcutaneous vs systemic things?
- LS: infection due to wounds
- systemic: infection widely spread inside host bodies
