L16 Fungi Flashcards
where did fungi emerge from
branch shared with animals
describe fungi in a general manner
- diverse
- widespread
- essential
why are fungi essential for well-being of most terrestrial ecosystems
they break down organic matter and recycle vital nutrients
main characteristics of fungi
- multicellular
- heterotrophic
- eukaryotic
- lack internal digestive system
how do fungi get their nutrients
absorb them from the outside, through cell walls
why are there problems with the fungi mode of digestion
- can’t access large organic molecules b/c they don’t cross cell walls/membranes
- can’t move to find food
what are solutions to the problems with the fungi mode of digestion
- secrete different enzymes to break down big molecules, absorbed by external digestion
- use growth of fungal body to find nourishment b/c sessile
describe fungal structure
- highly branched filaments (hyphae) and cell walls of chitin
- long, thin, hyphal threads that provide large surface area for absorbing nutrients
- hyphae grow at the tips, allow for ‘movement’ towards food sources
- hyphae make extensive network (mycelium)
coenocytic vs septate
multinucleate vs uninucleate
describe structure of recently evolved fungal groups
gained cross walls (septa) which divided hyphae into filaments of connected cells
describe structure of earliest fungi
lacked cross walls to separate cells (coenocytic)
why is cytoplasmic continuity along hyphae important
all raw materials for growth obtained from surroundings must be transported into cells across cell wall and membrane
role of fungi in carbon cycling
convert dead organic matter back to carbon dioxide and water
decomposing vs. parasitic vs. mutualist fungi
- feed on dead matter, breaking down cellulose and lignin, chemical cycling
- infect living tissues of protists, plants, animals (~30%)
- symbiotic interactions with other organisms
describe mutualist relationships that fungi maintain
- plants: mycorrhizae form fungal-root partners
- animals: leaf-cutter ants, termites, beetles
- cyanobacteria or algae (lichens)
what are the problems fungi face in completing their life cycle
- finding mates for genetic diversity
- dispersal to new habitats
what are solutions to fungi reproduction problems
- reproducing by spores
- asexual or sexual reproduction
what are the steps of fungi sexual reproduction
plasmogamy, karyogamy, meiosis
plasmogamy
fusion of cytoplasm of 2 haploid cells
- heterokaryotic or dikaryotic
karyogamy
nuclear fusion forming a zygote (diploid stage)
meiosis
haploid spores -> haploid hyphae -> haploid mycelium
what are the traits that allowed fungi to better adapt to life on land
- chitin cell walls
- hyphae
- septa
- complex multicellular fruiting bodies (sex. rep.)
describe the evolutionary trend in reproduction through fungal phylogeny
- asexual reproduction: chytrids, zygote, arbuscular mycorrhizal fungi
- sexual reproduction: sac, club fungi
what is the fungal lineage
- chytrids
- zygomycetes
- glomeromycetes
- dikarya (ascomycetes and basidiomycetes)
describe chytrids
- only fungi with motile flagellated spores (zoospores)
- only asexual reproduction
- mainly aquatic but some terrestrial
- can be decomposers, parasites, mutualists
describe zygomycetes
-lost flagellated spores
-have aseptate or coenocytic hyphae
-asexual reproduction and sexual reproduction
describe asexual reproduction in zygomycetes
- tips of some haploid hyphae make haploid sporangia
- sporangia make haploid spores developing into haploid hyphae (mycelium network)
describe sexual reproduction in zygomycetes
+ / - mating types
- haploid hyphae from 2 different fungal types come into contact
- hyphal tips fuse forming a gametangium
- haploid nuclei fuse to make diploid
- zygosporangium undergoes meiosis to produce haploid zygospores released from stalked sporangium for asexual reproduction
sporangium vs zygosporangium
asexual (haploid, n) vs sexual (diploid, 2n)
describe glomeromycetes
~50% of soil fungi
-asexual reproduction (occurs after sections of hypha are walled off)
-form symbiotic associations with plant roots (mycorrhizae)
-tremendous ecological importance
describe dikarya
separate monophyletic group of fungi
distinguished by presence of septa between cells
- to control # of nuclei per cell
- to produce dikaryotic cells through growth
- made complex, distinguished fruiting bodies for sexual reproduction
describe ascomycetes
most diverse group of fungi (in species #)
- asexual and sexual reproduction
describe asexual reproduction in ascomycetes
haploid asexual spores (conidia) made in asexual sporangia (conidiophores)
describe sexual reproduction in ascomycetes
haploid sexual spores (ascospores) are made in sexual sporangium (ascus) contained within specialized sexual fruiting body (ascocarp)
mitosis in ascomycetes (sexual cycle)
haploid (n)
meiosis in ascomycetes (sexual cycle)
diploid (2n)
describe basidiomycetes
- only sexual
- mushrooms, puffballs, shelf fungi, mutualists, and plant parasites
- most mushrooms are important decomposers of woody plant debris
describe sexual reproduction in basidiomycetes
haploid sexual spores (basidiospores) are produced on club-shaped sexual sporangia (basidia) that develop in specialized sexual fruiting body (basidiocarp)
stages of basidiomycete sexual cycle
- dikaryotic mycelium making dik. fruiting body and dik. basidia made (heterokaryotic)
- karyogamy completed to make diploid (2n) nuclei
- meiosis, dispersal + germination, plasmogamy (haploid, n)
what are the fungi
widespread, diverse, and essential group for chemical/nutrient processes
what are the characteristics of the fungi
multicellular, heterotrophic, eukaryotic, lack internal digestive system
- also developed complex traits to survive on land
how is the diversity of the fungi classified
-through interactions with other species
-molecular analyses for evolutionary relationships (making fungal phylogeny/lineages)
