topic 7B: fungi Flashcards
what are the two types of fungi?
(1) unicellular: such as yeasts (e.g. Saccharomyces cerevisiae)
(2) multicellular: e.g. mushrooms and molds
mushrooms and molds are types of?
multicellular fungi
regarding fungal morphology; what does the cell wall consist of?
chitin
some fungal species experience dimorphism, which is?
some fungi can grow both as filaments (multicellular) or yeasts (unicellular)
(depending on their environmental conditions, e.g. Blastomyces)
describe unicellular fungi (yeasts)
- usually form multicellular colonies
- reproduce by sexual or asexual reproduction (e.g. budding)
- example: Saccharomyces cerevisiae
describe multicellular fungi
- have a filamentous structure: consists of mycelia
- have filaments: called hyphae
what is mycelia? what function does it have?
- networks of branched hyphae (filaments)
- function: aids in nutrient absorption
the hyphae of most fungi are divided into cells by internal walls called?
septa
what are the types of hyphae?
(1) septate = with septa
- most fungi have hyphae divided into cells by septa
- pores allow cell-to-cell movement of organelles
(2) coenocytic fungi = aseptate
- lack septa
- have a continuous cytoplasmic mass with hundreds/thousands of nuclei
what are septa?
rings of hyphae cell walls
(function: divide hyphae into cells)
what are the ways asexual reproduction of fungi takes place?
(1) simple cell division (binary fission)
(2) budding: a new organism develops from an outgrowth (bud) that separates from the parental cell
what are sporangia?
spore-producing structures
describe sexual reproduction of fungi
production of diploid zygote (2n) from the fusion of 2 haploid (n) fungi (hyphae)
describe fungi reproduction
fungi reproduce by sexual or asexual reproduction by producing spores
the haploid (n) spores can be produced in 2 ways:
sexually or asexually
describe how haploid (n) spores can be produced sexually?
sexual reproduction:
- from the zygote by meiosis
- called sexual spores
- zygote (2n) => meiosis => spores (n)
describe how haploid (n) spores can be produced asexually?
asexual reproduction:
- by mitosis
- called asexual spores
- spore (n) => mitosis => spore (n)
(haploid spores produce even more haploid spores through mitosis)
what is the difference between haploid spores produced by sexual and asexual reproduction?
they are the same spores, just produced differently
what is another type of reproduction that fungi can undergo?
germination
what is germination?
- when, under favorable conditions, spores grow back to the vegetative cell (fungal cell)
- spore => germination => vegetative cell
which of the two is ALWAYS sporogenic: fungi or bacteria?
- ALL fungi is sporogenic
- only some bacteria is sporogenic
describe the fungal life cycle, undergoing sexual reproduction
(1) a mycelium fuses with another mycelium with the process of plasmogamy (cytoplasmic fusion) initially
(2) after the cytoplasms fuse, it goes through a heterokaryotic stage (2 different haploid nuclei that do not fuse right away)
(3) then the nuclei fuse together to cause karyogamy (nuclear fission) to create the diploid zygote
(4) the diploid zygote undergoes meiosis to produce haploid spores (called sexual spores as they are produced by sexual reproduction - meiosis)
(5) these spores undergo germination when found in optimum conditions (such as in the human body) to create mycelium
(6) these mycelia can fuse together to repeat the process
describe the fungal life cycle, undergoing asexual reproduction
(1) haploid mycelium can itself undergo mitosis (asexual reproduction) and produce in the sporangia even more haploid cells
(2) again, through germination can lead to formation of mycelium (process repeats)
2 haploid mycelia fuse together to create a diploid zygote
sexual reproduction of fungi
the process of producing a haploid cell through mitosis is ONLY present in?
only plants, protists, and fungi, and NOT IN ANIMALS
fungi nuclei are normally _____?
haploid
what do we have instead of genders in fungi?
- different mating types
sexual reproduction = fusion of hyphae from different mating types
what are the sexual signaling molecules fungi use to communicate their mating type?
pheromones