Lecture 17: Fungus

Question 1

how do fungi fit onto the Eukaryotic tree?

Answer 1

more closely related to animals than plants

-it’s its own monophyletic clade

Question 2

unifying fungal traits

Answer 2

• a number of cell types or unicellular
• heterotrophs that absorb nutrients
• cell wall with chitin
• some have dikaryon stages
• both sexual and asexual reproduction
• three styles of nutrient acquisition

Question 3

chitin

Answer 3

-polysaccharide that stiffens their cell walls (& gives them structure)

Question 4

cell types in fungi

Answer 4

-unicellular; can be flagellated (i.e. yeast) or multicellular (filamentous)

Question 5

hyphae on the fungal body

Answer 5

-long chains of cell-like structures that are joined

Question 6

septa on the fungal body

Answer 6

• divides cells
• not a complete barrier bc they have pores
• allows for free flow of cytoplasm
• fungi w/ septa are called septate fungi

Question 7

coenocytic fungi

Answer 7

• don’t have septa

- indicates that cell separation isn’t that important in fungus

Question 8

mycelium on the fungal body

Answer 8

-groups of hyphae bundled together

Question 9

fungal digestion/absorptive heterotrophy

Answer 9

• secretes digestive enzymes around them
• enzymes digest what they land on–> absorb organic materials
• external digestion
• nutrients must be in water

Question 10

how does the fungal body plan reflect nutrient intake in fungus?

Answer 10

-no really defined cells so nutrients can travel faster, therefore fungi grow FAST

Question 11

cell walls in fungi

Answer 11

-have chitin (not cellulose) (same material as insect exoskeleton) and gives them their structure

Question 12

fungal nuclei and dikaryons

Answer 12

• dikaryons form from the fusion of 2 haploid mating strains
• rarely differentiation between male and female, instead have mating types (members of same one can’t mate together, lead to greater genetic variation)

Question 13

dikaryon formation

Answer 13

• fuse
• haploids exist independent but both are transcribed which protects them from bad mutations that happen to haploids (like in mosses)

Question 14

Asexual and sexual reproduction can occur in one life cycle

Answer 14

-asexual makes more spores, while sexual goes through plasmogamy, fertilization, karyogamy, and makes spores

Question 15

how are pores reproductive structures?

Answer 15

-by wind they turn into new individuals; produce new spores by mitosis

Question 16

plasmogamy

Answer 16

• cell fusion

- fusion of cytoplasm

Question 17

karyogamy

Answer 17

• fertilization

- fusion of nuclei

Question 18

importance of sexual stages for identification

Answer 18

• sexual stages are used to identify fungus

- making it hard to finalize the fungal phylogeny

Question 19

microsporidia

Answer 19

• tiny, obligate, intracellular parasites
• infect with a polar tube and then replicated by host cell
• cause things like weight loss
• lack true mitochondria

Question 20

mitosome

Answer 20

• has double membrane
• looks like mitochondria
• derived from mitochondria, indicates they were lost.
• after this the microsporidia branched off

Question 21

chytridiomycetes

Answer 21

• likely paraphyletic
• aquatic, unicellular life stages
• flagella present, coenocytic
• can be found in the stomachs of cattle

Question 22

amphibian decline

Answer 22

• chytrids may be cause bc they kill amphibians that they reside on by producing harmful spores (deadlier at colder temps)
• types: batrachochytrium dendrobatidis (kills amphibians)

Question 23

zygomycetes

Answer 23

• saprobic or parasitic
• terrestrial, no septa, coenocytic
• sexual reproduction is rare, but still produce zygotes
• gametangia, zygosporangium, and zygospore are found in ONLY this life cycle

Question 24

gametangia

Answer 24

• are mycorrhizal
• coenocytic
• don’t form mycelia (remain single strands)
• can’t live without host
• all terrestrial

Question 25

zygosporangium

Answer 25

- gametes mate in it - leads to many unfused nuclei - once they fuse, you get a multinucleate

Question 26

zygospore

Answer 26

- multinucleate - all nuclei inside are 2n - can remain dormant and eventually portions of it will undergo meiosis and produce spores

Question 27

glomeromycetes

Answer 27

- only 150 species and made invasion of land by plants possible - coenocytic - don't form mycelia

Question 28

mycorrhizae

Answer 28

- form mutualistic relationships with plants - hyphae grow in roots of trees and plants - allows for beneficial nutrients exchange for both - they can't live without their hosts b/c get their sugars from the host's photosynthesis - monophyletic

Question 29

ascomycetes

Answer 29

- septate - dikaryon forming but short dikaryon phase and then becomes diploid - bear spores in cups - types: cup fungus, yeast, penicillin, truffle/morels, cheese molds, chestnut blight, dutch elm disease.

Question 30

basidiomycetes

Answer 30

- most well known, contains most mushrooms - basidiocarps (puffball reproductive structures) - septate and dikaryon forming - dikaryon stage can persist for years

Question 31

mutualists

Answer 31

- exchange nutrients with other species | - live in conjunction with other species

Question 32

saprophytes

Answer 32

- digest/eat dead materials | - "decomposers"

Question 33

parasites

Answer 33

- eat living tissue on living organisms | - types: athlete's foot, ringworm

Question 34

why are fungal diseases so hard to treat?

Answer 34

- bc they typically attack other eukaryotes | - its hard to treat the fungus without "treating" the host.