Download Chapter 20 Fungus Main Ideas: Fungi are unicellular or multicellular

Chapter 20 Fungus
Main Ideas:
1. Fungi are unicellular or multicellular eukaryotic heterotrophs that are
decomposers.
2. Fungi exhibit a broad range of diversity and are classified into four major
phyla.
3. Lichens and mycorrhizae demonstrate important symbiotic relationships between
fungi and other organisms.
I. FUNGUS
A. Characteristics
1. found everywhere
2. bright & colorful or dull & unnoticed
3. thrive in warm moist ENVRs, but can survive at lower temps
4. use to belong to plant kingdom, but are now its own kingdom
5. multicellular/unicellular
B. Major Features in Fungi
1. cell wall contains chitincomplex carb. that is strong & flexible
2. basic structurethreadlike filaments called hyphae
a. hyphae develop from spores
b. hyphae elongate at their tips & branch into a networkmycelium
c. different types of mycelium based on their function
1. anchor the fungus
2. invade food source
3. form reproductive structuresfruiting body
d. hyphae have septa which divide the hyphae into individual cells
e. septa are porousallowing cytoplasm & nutrients to flow easily b/t
areas
f. advantage=nutrients dispersed quickly
C. Nutrition in Fungi
1. heterotrophs-->use extracellular digestion
a. hyphae grow into a food source
b. hyphae release enzymes that break-down large molecules into
smaller ones
c. smaller ones diffuse into hyphae & enter cytoplasm-->growth, repair,
& reproduction
d. as mycelium grows, it grows & can cover more area=more nutrients
2. saprophytesdecomposers
3. parasitic fungi produce specialized hyphae-->haustoria
a. haustoria-->penetrate & grow into host cells
b. advantage=can directly absorb nutrients
4. mutualisticmycelium grows around the root of a plant
a. fungus receives sugar from the host plant
b. mycelium increases H20 uptake & mineral absorption for the host plant
D. Reproduction
1. fungi are classified by their structure & patterns of reproduction
2. depends on species & environmental conditions
3. can be sexual/asexual
4. asexual reproduction
a. fragmentation-->pieces of hyphae break off a mycelium & grow into
new mycelium
b. budding-->unicellular fungi=>yeast
1. occurs via mitosis & a new individual cell pinches off from a parent
c. spores-->haploid reproductive cells w/ a hard outer coat; most fungi
produce spores
1. in favorable conditions a threadlike hypha will emerge & grow
from a fungal spore forming a new mycelium
2. mycelium will establish itself in the food source
3. another type of specialized hyphae can grow away from the
mycelium & it produces a spore containing structure-->sporangium
4. sporangium-->a sac/case in which spores are produced
5. advantages-->sporangium protects spores & produces a large
number of spores at 1 time
6. also spores are small/lightweight & therefore easily dispersed
II. Ecology of Fungi
A. Lichens
1. mutualistic relationship w/other organisms
2. symbiotic association b/t a fungus & a photosynthetic green
algae/cyanobacterium
3. fungus portion forms a web of hyphae in which algae/cyanobacteria grow
4. lichens only need light, air, & minerals to grow
5. algae/cyanobacteria provide the food for both organisms
6. fungus provides water & minerals it absorbed from rain & air & protects it
from environmental changes
7. pioneer speciesfirst to colonize a barren area
8. bioindicatora living organism that’s sensitive to changes in the ENVR
conditions & is 1 of the 1st organisms to respond to changing conditions
B. Mycorrhizamutualistic relationship in which a fungus lives symbiotically with
plant roots
1. mostly basidiomycotes
2. hyphae grow around the roots of plantincreases absorptive surface of
roots
a. hyphae absorb nutrients & water & then release them into roots
b. the fungus benefits by receiving nutrients(sugars & AA) from plant
c. plants w/mycorrhiza grow bigger & faster