Lecture 13 Flashcards
Kingdom Fungi
within Opisthokonta clade along with Animalia, colonized land around 475 MYA possibly as symbionts of plants
5 main groups of fungi
- Chytridiomycota
- Zygomycota
- Glomeromycota
- Ascomycota
- Basidiomycota
6 fungi characteristics
- chemoheterotrophs
- external digestion
- cell walls made of chitin
- bodies composed of hyphae
- large surface area:volume ratio (due to filamentous structure)
- produce haploid spores asexually or sexually
external digestion
secrete powerful enzymes outside body, break down large complex organic molecules (cellulose/lignin in plants and chitin/keratin in animals) into small, simple ones absorbed by body
chitin
nitrogenous polysaccharide that evolved independently in some invertebrates, makes up cell wall in fungi
hyphae
delicate chitin tubes surrounding cytoplasm that compose bodies of fungi
mycelium
interwoven hyphal mat, acts as feeding network, can be very large
2 types of hyphae
- septate
2. coenocytic
septate hyphae
have cross-walls (septa) dividing cells into separate
chambers, but holes in walls allow
cytoplasm and sometimes nuclei to travel through
coenocytic hyphae
lack cross walls, continuous cytoplasm with hundreds
or thousands of nuclei
hyphae growth
more area for enzyme secretion and food absorption, can grow quickly because proteins are sent to growing tips, only grow in length
fungal spores
asexually or sexually, always haploid, produce hyphae
non-chytrid fungal life cycle - haploid stages
hyphae and spores
non-chytrid fungal life cycle - diploid stage
transient single-celled zygote formed during sexual reproduction, undergoes meiosis to make haploid spores (do not show alternation of generations)
gametes/separate sexes
not present in fungi, zygote created by any haploid nuclei
sex in fungi
- plasmogamy –> heterokaryon
2. karyogamy
plasmogamy
fusion of cytoplasm of genetically different individuals, nuclei are separate
heterokaryon
a mycelium with 2 or more different genotypes of separate nuclei, may remain in this state for a long period of time so flaws from one genome can be compensated for by the other