Ch 32: Fungi

Question 0

Hyphae in Fungi

Answer 0

• Long, slender filaments in
  multicellular fungi
• May have more than 1 nucleus
   (monokaryotic or dikaryotic)
• Sometimes many nuclei intermingle in 
  common cytoplasm of fungal 
  mycelium
• Some are continuous, others are
   divided by septa
• Cytoplasm flows through hyphae
     – Allows rapid growth under good 
        conditions
• Mycelium: mass of conn hyphae
• Grows through and digests its
   substrates

Question 1

Fungi

Answer 1

• Single-celled or multicellular 
• Sexual or asexual 
• Heterotrophic
• Specialized to extract and absorb 
   nutrients & surroundings

Question 2

Chitin in fungi

Answer 2

• Cell walls include chitin
• Also found in hard shells
(exoskeletons) of arthropods

Question 3

Reproduction in fungi

Answer 3

• Capable of sexual & asexual
• Sexual rep
   – 2 haploid hypha of compat 
      meeting types fuse
        • Some fungi fusion immed 
          results in diploid cell
        • Others have dikaryon stage
           (1n + 1n) before parental nuclei 
           form diploid nucleus
• Spores- most common means of rep

Question 4

Heterokaryotic/Homokaryotic

Answer 4

• Hetero:
nuclei from genetically distinct individuals

• Homo:
nuclei are genetically similar to one another

Question 5

Mitosis in fungi

Answer 5

• Cell is not relevant unit of rep
• Nuc envelope does not break down
  & reform
      – Instead spindle apparatus 
         forms within
• Fungi lack centrioles
      – Spindle plaques regulate
         microtubule formation 
         during mitosis

Question 6

Nutrition

Answer 6

• Obtain food by secreting digestive 
   enzymes into surroundings
• Then absorb org molecules prod by 
  external digestion
• Fungi can break down cellulose and 
  lignin
     – Some fungi are carnivorous

Question 12

Microsporidia

Answer 12

• Obligate, intracellular, animal
parasites
• Long thought to be protists
• Lack mitochondria

Question 13

Blastocladiomycetes

Answer 13

• Unflagellated zoospores

* Haplodiplontic lifecycle

Question 14

Neocallimastigomycota

Answer 14

• Digest plant biomass in mammalian
   herbivore rumens
      – Mammal depends on fungi 
         for sufficient calories
• Greatly reduced mitochondria lack
   cristae
• Zoospores have mult flagella
• Horiz gene transfer brought 
  cellulase gene from bacteria 
  into Neicallimastix genome

Question 15

Endophytic fungi

Answer 15

• Live in the intercellular spaces inside plants
• Some parasitic, some commensalistic
• Some protect hosts from herbivores
by producing toxins

Question 16

Fungi Symbioses

Answer 16

• Obligate symbiosis: need to survive
• Facultative symbiosis: nonessential
• Pathogen: cause harm & disease
• Parasites: cause harm, not disease

• Commensal relations:
benefits 1 & doesn’t harm other
• Mutualistic relationships:
benefits both partners

Question 17

Lichens

Answer 17

• Symbiotic assoc bet. fungus & 
  photosynthetic partner 
• Most are mutualistic
• Fungi in lichens can't grow normally 
  w/o photosynthetic partner

Question 18

Fungal diseases

Answer 18

• Difficult to treat because close
phylogenetic relationship bet.
fungi & animals

Question 20

Chytridiomycota

Answer 20

• Aquatic
• Flagellated
• have motile spores: zoospores
• Produce haploid gametes in sexual rep or diploid zoospores in asexual rep

Question 21

Zygomycota

Answer 21

• Multinucleate hyphae lack septa
(except rep structures)

Sexual reproduction
• Fusion of gametangia
• Haploid nuclei fuse to form diploid 
   nuclei (karyogamy)
• Develops into zygosporangium
   where zygospore develops.
• Meiosis occurs during germination
   of zygospore
        – Releases haploid spores

Asexual reproduction more common
• Sporangiaphores have sporangia that
release spores

Question 22

Glomeromycota

Answer 22

• Form intracellular associations with 
  plant roots called arbuscular 
  mycorrhizae
     – provide plant with minerals
     – can't  survive w/o host plant
• No evidence of sexual reproduction
• Multinucleate hyphae lack septa
• rep asexually

Question 23

Ascomycota

Answer 23

• In sexual rep ascospores form 
  inside sac (ascus) from karyogamy
• Asci differ in ascocarp
• Meiosis & mitosis follow, prod a 
  haploid nuclei that become walled
  ascospores
• Ascospores release, land, & 
  germinate
• 2 mating strands come together;
  form dikaryotic hyphae (grows into 
  ascus)

• Asexual rep also common

Question 24

Basidiomycota

Answer 24

• In sexual rep, have club-shaped rep 
  structures called basidia
• In basidia, fusion of 2 nuclei from 
  different mating types occurs
• Meiosis follows
   – 4 haploid products are inc into
      Bspores (bspores released)
• Bspores land, germination leads to 
   prod of monokaryotic hyphae

Asexual rep very common
• Conidia formed at ends of modified
  hyphae called conidiophores
• Allow for rapid colonization of new 
  food source
• Many conidia are Multinucleate