CHAPTER 22
FUNGI
BIOLOGY II – LOULOUSIS
22.1 CHARACTERISTICS OF FUNGI
• Fungi grows in one place until its food runs out
• Before it dies, it releases millions of spores that
float through the air until they find food
• Cycle begins again
WHAT ARE FUNGI?
• »All fungi share three characteristics
• 1. Threadlike bodies
• 2. Cell walls have chitin
• 3. Heterotrophic
1. FUNGI HAVE THREADLIKE BODIES
•Made of long slender filaments
•Filaments weave together to
form fungus body and
reproductive structures
•Most filaments are loosely
woven
•Reproductive structures are
tightly woven
•Like mushrooms
FUNGI COLORS
• Fungi get their color from chemicals that form
during metabolic processes
• Most of the colorful chemicals are toxic
2. FUNGAL WALLS CONTAIN CHITIN
• A tough carbohydrate found in the cell walls
3. FUNGI ARE HETEROTROPHIC
• Fungi are not plants
• Do not contain chlorophyll, not autotrophs
• Obtain nutrients by secreting digestive
enzymes that break down organic matter in
their environment
• Absorb decomposed molecules
• Absorb nutrients
• non-living matter
• Leaves, branches, dead animals, & waste
• Resource recyclers
STRUCTURE AND FUNCTION
• »Fungal body is made of filaments, which increase
the surface area allowing fungus to absorb nutrients
more efficiently
STRUCTURE OF A MUSHROOM
BODY STRUCTURE
• Hypha- a filament of fungus, threadlike
• These cells are haploid and identical
• Have cell walls called septa that separate
• Mycelium- mass of fungal filaments composes body
• Meters long, underground
• Sometimes form root-like structures rhizoids that hold
fungi in place and absorb nutrients
Hyphae
Mycelium
Septa
HYPHAE STRUCTURE
OBTAINING NUTRIENTS
Ringworm
• Release enzymes to break down organic
and inorganic matter for nutrients
• Absorb across cell walls
• Saprobes- absorb nutrients from dead
organism
• Recycle nutrients in ecosystem
• Parasite-absorb nutrients from living host
• Cause disease like athlete’s foot and
ringworm
REPRODUCTION
• »What is the difference between sexual and
asexual production of spores in fungi?
• Sexual – spores are produced by meiosis
oAllows for genetic diversity
• Asexual - spores are produced by mitosis
oAllows for rapid dispersion
• Most fungi do both asexual and sexual
reproduction
SEXUAL REPRODUCTION
• Fused hyphae form sexual
reproductive structure (like mushroom)
• Spores form through fusion of two
genetically different nuclei.
• Now the nuclei are diploid and
undergo meiosis to produce haploid
spores
ASEXUAL REPRODUCTION
• Specialized hyphae produce
stalks
• At tips of stalks haploid spores are
produced by mitosis
• Genetically identical to parent
• Imperfect fungi – fungi without a
sexual stage
YEAST
• Unicellular stage of fungi
• Reproduce asexually by budding
• Occasionally form multicellular hyphae and
reproduce sexually
MOLD
• Rapidly growing, asexually reproducing stage of
some types of fungi
• “mold” refers to asexual phase
22.2 GROUPS OF FUNGI
• Modern fungi classified into four phyla
• Chytridomycota (chytrids)
• Zygomycote (zygote fungi)
• Ascomycota (sac fungi)
• Basidiomycota (club fungi)
• Classified based on type of reproductive
structures they form
CHYTRID FUNGI
• Date back 500 million years
• Earliest fungi produced spores and gametes with
flagella
• First fungi probably appeared in water
• Only group of modern fungi in water chytrids
CHYTRID FUNGI, CONT.
• Have chitin in their cell walls
• Digest food outside their bodies
• Produce hyphae that form rhizoids
• Hold chytrids in place and absorb
nutrients .
• Sexual reproductive structures contain
spores.
CHYTRID FUNGI, CONT.
• Most are aquatic
• Can live on moist land
• Mainly saprobes
• Which…feed on dead algae or plants
• Some are parasites
• Common parasites of aquarium fish
• Reason for decline in amphibians in the wild
**BATRACHOCHYTRIUM
DENDROBATIDIS
• One of biggest threats facing
amphibians worldwide
• Mechanism by which it kills is
unknown
• No known treatment once
infected
ZYGOTE FUNGI
• Common member of phylum Zygomycota
• Named for sexual reproductive structures
that produce zygotes inside a
zygosporangium
ZYGOTE FUNGI
SEXUAL REPRODUCTION
• Begins when hyphae from two mating types
join
• Different mating types not referred to as
male and female
• Why? Because they are physically
identical
• Instead “+“ and “–”
ZYGOTE FUNGI
SEXUAL REPRODUCTION
• Tough capsule called zygosporangium forms
• Resistant to? Hot, cold, and dry conditions
• When conditions are right, nuclei fuse to
form diploid (2n) zygotes
• Zygotes undergo meiosis
• Zygosporangium germinates, which
produces a sporangium that
releases haploid spores.
ZYGOTE FUNGI
ASEXUAL REPRODUCTION
• More common than sexual reproduction
• Haploid spores are produced in sporangia
at the tips of hyphae
• Haploid spores produced by mitosis
• Haploid spores are carried by wind to new
places
rhizopus
LIFE CYCLE OF ZYGOTE FUNGI
ZYGOTE FUNGI
• Usually live in soil
• Feed on decaying plant and animal matter
• Some species of Rhizopus can cause cancer
CHECK POINT
• Where does meiosis take place in
zygote fungi?
• Zygosporangium
**ZYGOMYCETE PILOBOLUS
• Grows in animal dung
• Produces reproductive structures about 5 to
10 mm high
• Can eject spores up to 2 m at a velocity
near 50 km/h
SAC FUNGI
• Phylum Ascomycota
• Characterized by an ascus
• Saclike sexual reproductive
structure that produces spores
• Ascus means “sac”
SAC FUNGI
SEXUAL REPRODUCTION
• Hyphae of different mating types grow
together
• Hyphae fuse to form a bridge
• The nuclei pair up, one + and one –
• Divide to form mass of hyphae that
contain two nuclei per cell
SAC FUNGI
SEXUAL REPRODUCTION
• In most sac fungi, mass is dikaryotic, having
two nuclei
• Forms structure called ascocarp
• Cells in ascocarp becomes saclike asci
• Nuclei fuse and undergo meiosis
• Haploid spores are released
SAC FUNGI
ASEXUAL REPRODUCTION
• Usually reproduce asexually
• Asexual spores called conidia form by
mitosis on hyphae called conidiophores
• Conidia form in chains and are not covered
• Spores carried by wind to germinate
LIFE CYCLE OF ASCOMYCOTA
CHECK POINT
• In sac fungi, which structure is
dikaryotic?
• Answer: ascocarp
**SAC FUNGI
ASCOMYCOTA
• Cause many plant diseases
• Wiped out virtually all chestnut trees in US around
1980
• Resistant cultivars are now being planted
• Also known for important contributions to human
health
• Penicillum – antibiotic penicillin
CLUB FUNGI
• Phylum Basidiomycota
• Include mushrooms, toadstools, puffballs,
jelly fungi, shelf fungi, rusts and smuts
• Larges known club fungus in Oregon is 3.5
miles across!
• Characterized by a basidium
• Which is a clublike sexual reproductive
structure that produces spores
CLUB FUNGI
SEXUAL REPRODUCTION
• Specialized hyphae of different mating types
grow together
• Hypha from one fuses with hypha from
another forming dikaryotic cell
• Nuclei remain separate as the cell grows
into new mycelium, in which cell has 2
nuclei
• Grows rapidly
• When conditions are right, mycelia form
reproductive structure called basidiocarp
• Ex – mushroom
SEXUAL REPRODUCTION CONTINUED
• Under basidiocarp there are clubshaped cells called basidia in which
the two nuclei fuse
• meiosis occurs and spores produced
• Spores carried by wind, then grow
STOP AND THINK
• What might be the reproductive
advantage of having gills on the
underside of the mushroom?
• Protect spores from rain or make it
easier for spores to disperse.
CLUB FUNGI
ASEXUAL REPRODUCTION
• Rare
• Does occur in some rusts and smuts
LIFE CYCLE OF BASIDIOMYCOTA
CLUB FUNGI
CHECK POINT
• Which type of fungi was classified
with protists until recently?
• A. chytrid fungi
• B. club fungi
• C. sac fungi
• D. zygote fungi
• Answer: A chytrid fungi
FUNGAL PARTNERSHIPS
• Fungi form Partnerships
• In a mutualistic relationship.. Both members benefit
• Lichen
• Fungus with photosynthetic partner
• Photosynthetic partner provides carbohydrates
• Fungus provides protected environment, vitamins, minerals
• Can survive in extreme environments
• Can be damaged by chemical changes
• Serve as living indicators of air pollution
FUNGAL PARTNERSHIPS
• Mycorrhiza
• Fungi and roots of most plants
• Photosynthetic partner provides
carbohydrates
• Fungus provides phosphorus and
mineral from soil to roots
LICHEN
• Partnership between fungus and photosynthetic
organism such as cyanobacteria or green alga
MYCORRHIZA
• Association between fungus and roots of nearly
ALL plants
FUNGI PHYLA
Method of
reproduction
Chytridiomycota
Zygomycota
Ascoymycota
Basidiomycota
Structures
Habitat
Example(s)
22.3 FUNGI AND HUMANS
• Fungi are used for food, medicines, research,
alternative fuels and pest control
• Most familiar as a food
• Provide flavor and color of blue cheese
• Yeasts are used in baking, brewing, and
winemaking
• Produce citric acid that is used in soft drinks and
candies
• Some, liketruffles, are worth $1,000 per pound
• Produce the antibiotic penicillin and
cephalosporin
• Black bread mold produces cortisone
• Used to treat skin rashes and to reduce joint
swelling
• Yeast cells modified to make vaccine for hepatitis
B.
• Yeast also produces gasohol, a fuel alternative
• Fungal insect parasites are used to kill cropdestroying insects
• Helps reduce use of harmful pesticides
FUNGI AND THE ECOSYSTEM
• Fungi play important ecological roles by
decomposing organic matter and by breaking
down and absorbing minerals from rocks and
soil
• Main role in ecosystem decomposition
• Can also break down wood
FUNGI AND THE ECOSYSTEM, CONT.
• Through lichens, fungi slowly break down
rocks and prepare environment for other
organisms
• Through mycorrhizae, fungi absorb minerals
from the soil and transfer them to plant roots
• Almost all plants have mycorrhizae
• Some, could not survive without them
FUNGI AND DISEASE
• Can causes disease in plants and animals
• Cause disease by absorbing nutrients from
host tissues and by producing toxins.
FUNGAL INFECTIONS
• Dermatophytes are fungi that infect skin
and nails
• Cause athlete’s foot, toenail fungus, and
ringworm
• Yeast is normal resident of body
• Antibiotics, hormonal changes, or illness
can cause overgrowth of yeast
• Causes yeast infection in reproductive
organs and in mouth
FUNGAL INFECTIONS
• Histoplasmosis is lung infection caused by
fungus
• Grows in bat and bird feces
• Occurs when spores are inhaled
• Left untreated, is fatal
FUNGAL TOXINS
• Many produce dangerous toxins
• Can cause vomitting, diarrhea, liver damage,
and even death
• Aflatoxins – contaminates corn, peanuts, and
cottonseed
• Can cause liver cancer
• Indoor molds aggravate allergies
• Mold toxins can be linked with pulmonary
bleeding in infants