Lecture 21 Flashcards Preview

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Flashcards in Lecture 21 Deck (15):
1

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

2

What is the mushroom we see above the ground?

it is just a reproductive structure, most underground

3

What are fungi often used for?

-medicine, antibiotics= attack living tissue as well

4

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

5

How do fungi act as pathogens to plants?

6

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

7

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

8

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

9

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

10

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

11

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

12

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

 

13

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

14

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

15

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