fungi

Question 1

properties of fungi

Answer 1

• chitin in cell walls (structural polysaccharide)
• absorptive heterotrophy
• mostly multicellular
• unicellular species (yeast) in most groups, some fungi have yeast lice cycle stage
• mycelia
• hyphae

Question 2

mycelia

Answer 2

• body of multicellular fungus
• high surface area to volume ratio which is advantageous for maintaining nutrients but a disadvantage when it comes to retaining water, so fungi are restricted to moist environments

Question 3

hyphae

Answer 3

• tubular filaments strengthened by chitin
• have direct contact with the environment for nutrient absorption

Question 4

septate hyphae

Answer 4

• septa subdivide hyphae cells
• incomplete, allows for movement of organelles and nuclei

Question 5

coenocytic hyphae

Answer 5

• undivided multinucleate hyphae

Question 6

rhizoids

Answer 6

• modified hyphae
• some anchor fungus to substrate
• do not absorb nutrients or water

Question 7

saprobic fungi

Answer 7

• major decomposers, critical to life cycle
• some can decompose lignin and keratin
• gain energy from carbon and nitrogen recycling

Question 8

falcultative parasitic fungi

Answer 8

• can grow on living organisms or independently
• e.g. honey fungus, parasitic on tree until it kills tree, then saprobic on dead tree

Question 9

obligate parasitic fungus

Answer 9

• only live on living hosts
• specialised nutritional requirements
• common hosts are plants and insects

Question 10

pathogenic fungi in humans

Answer 10

• often mild e.g. athletes foot, ringworm
• can be deadly especially if immunocompromised e.g. pneumonia, thrush

Question 11

pathogenic fungi, amphibian decline

Answer 11

• chytrid fungus
• thickens skin so amphibian cannot respire
• human influence e.g. species introduction accelerating it

Question 12

predatory fungi - common strategy

Answer 12

• sticky substance secreted from hyphae trap prey
• hyphae invade prey, absorbing and killing it

Question 13

predatory soil fungi species

Answer 13

• 3 cell constricting ring formation
• nematode stimulated fungus by crawling through ring
• cells swell and trap worm
• hyphae, invade, digest and kill worm

Question 14

mutualistic fungi, lichens

Answer 14

• symbiotic relationship with fungus and photosynthetic microbe (unicellular green algae, cyanobacteria or both)
• microbe gains favourable environment
• fungi obtains fixed carbon

Question 15

lichens, habitat

Answer 15

• can tolerate extreme environments
• primary colonisers of bare rock
• take up minerals from air, rain or dust
• acidify environment causing rock breakdown and soil formation

Question 16

lichen body forms

Answer 16

• crustose
• foliose
• fruticose

Question 17

lichen, reproduction

Answer 17

• asexual reproduction through fragmentation of thallus (vegetative body) or detachment and dispersal or Soredia (photosynthetic cells with hyphae wrapped around them) that then develop into new thallus
• sexual reproduction through the production and dispersial of haploid spores

Question 18

mutualistic fungi, mycorrhizae

Answer 18

• symbiotic relationship between vascular plants and fungi
• fungus obtains organic compounds
• fungus increases plant’s absorption on water and minerals (especially phosphate)
• fungus provides certain growth hormones and protection against microbial pathogens

Question 19

ectomycorrhizae

Answer 19

• fungus wraps around root
• no cell wall penetration
• healthy forests depend on them

Question 20

arbuscular mycorrhizae

Answer 20

• enter root and penetrates cell walls

Question 21

endophytic fungi

Answer 21

• lives in plants above ground
• non-harmful
• toxic to herbivores
• increases resistance to drought and salt stress