Lecture 21 Flashcards
Where did fungi evolve?
-also evolved in water, came out later as they needed something to decompose on land first -almost no fossil record of those= too soft
What is the mushroom we see above the ground?
it is just a reproductive structure, most underground
What are fungi often used for?
-medicine, antibiotics= attack living tissue as well
What is the structure of a fungi?
Fungi are heterotrophic food absorbers, and the vegetative (feeding) structure is a mycelium
- Mycelium is a network of hyphae: monofilaments (cytoplasm in a tube) with large surface area/volume ratio • Cell walls are chitin microfibrils embedded in a matrix of polysaccharides, protein & lipids
- Hyphae grow and branch, secrete and absorb, only at their tips.
- Hyphae may be divided by cross walls called septa. Septa are incomplete, and allow cytoplasmic continuity -only tips grow and absorb= when chitin wall formed nothing gets in not even water -everything happens at the tips -lot of nuclei but not divided into cells= septasemic -septa= incomplete walls -we call it a cell= but not really
How do fungi act as pathogens to plants?
How do fungi grow?
- Mycelia are capable of indefinite growth - large biomass!
- Unicellular yeasts divide by budding
- because of growing at the tips= indefinite growth
- largest organisms- fungi 2000 ha large! based on tip growth as long as they have enough food
How do fungi reproduce?
- By non-motile sexual and/or asexual spores (1N),which are long living Otzi boots= 5300 years,very resistent spores, always haploid, have sunscreen against sunlight -spores are everywhere -mushroom circles= usually will be the same mycelium)
- In fungi, the zygote is the only diploid cell (2N).
• Hyphae can fuse at their tips, forming cells with mixed nuclei (heterokaryons).
• Dikaryons (n+n) formed by plasmogamy of
compatible mating types
–sex at the tips, zygote is the only diploid! everything else haploid(exact opposite of humans)
-when two hyphae meet (must be compatible) plus and minus strand at tips=they fuse at the tips= new hyphae with both nuclei = dikaryon and they continue like that and the nuclei don’t fuse till they’re in the mushroom and there fusion= myosis
sometime heterokaryon-more nuclei
What are zygomycota?
-phulum of fungi
• Hyphae are coenocytic (no regular septa)
- Sexual spores are zygospores
- Zygospores formed by gametangial fusion
- Meiosis occurs during zygospore germination
- Asexual spores are sporangiospores
- e.g. fruit moulds, insect pathogens
List five features defiing the fungi kingdom?
• Heterotrophic food absorbers
• Mycelium of haploid hyphae that
grow only at the tips.
- Walls of chitin
- Reproduce by non-motile spores
- Zygote is the only diploid cell
List three features that distinguish the Oomycetes and Fungi?
- oomycetes have walls of cellulose while fungi= chitin
- oomycete hyphae are diploid and fungal hyphae are haploid
- oomycetes have flagellated zoospores fungi spores= non motile-thatś why people knew oomycetes were related to brown algae not fungi
How and where do Fungi live?
• Heterotrophs
• Secrete enzymes & digest
their food externally, then
absorbed it
• Reserves stored as
glycogen, fats & oils • Wide environmental tolerance
• Produce millions of non- motile spore
-sometimes specific, lot of them will only feed on just one type of thing while other can eat many decomposing things
What are saprophytic Fungi?
- Major recyclers
- Decompose cellulose, chitin & lignin
- Environmental tolerance means they grow everywhere other organisms are found
- major group of fungi
- break down everything! they don’t usually break down their own chitin though
Whata are the applictaions of fungi?
- Fungi will infect and recycle anything they land on!
- Fungi can have a role in seed exposure & dispersal in fruits.(some fruits only germinate only if the outer wall of frtuit attacked by fungi)
- • Suppress competitors using antibiotics and toxins (fungi compete with bacteria= for bodies= or with other fungi)= deadly toxins to prevent the other fungi from eating them
- the ytry to get their spores far away from their body so they don’t self-fertilize
Are some fungi parasitic?
- yes
- • Specialised structures & nutrition
• Rusts, blights, wilts and rots of plants
-Parasitic Fungi are everywhere
- Mycoses and allergies
- Predators - nematode- trapping fungi
ergot poisoning= (on grains)-the reproductive bit looks like a grain
-basis for LSD, Joan of Ark and salem witches had ergot poisoning= grandiose speeches and so on
–we have a good immune system against fungi, if HIV often die of fungal infections
Who with do fungi form symbiotic associations?
- Mycorrhiza=a symbiotic association between a fungus and the roots of a plant.(fungi forming association with plants -fungi break down bits and feed plant and plant gives ot photosynthetic products)
- Endophytes
- Lichens =symbiosis between a fungus and alga (or cyanobacteria)(-alga or cyanobacteria= photosynthetic bit feeding the
-fungi= completely different from animals)
- Invertebrates
- Vertebrates
