Chapter 24: Fungi
Characteristics of Fungi
Mode of Nutrition
 Fungi are heterotrophs
 Most are saprobes
 Saprobes – obtain nutrients from nonliving organic matter and so cause it to
decay
 Others are parasites
 Parasites – extract nutrients from tissues of a living host
 Without the fungi (and heterotrophic bacteria) organisms would slowly
become buried in their own waste and life could not go on.
 56,000 known fungal species and at least a million more unknown species
 Fungi evolved before 900 million years ago
 Some moved onto land 430 million years ago
Survey of Fungal Groups
 Zygomycetes (Zygomycota)
 Sac Fungi (Ascomycota)
 Club Fungi (Basidiomycota)
 The vast majority of species are multicelled
 Other kinds of fungi known as “imperfect fungi” are lumped together, but not
in a formal taxonomic group.
Key Features of Fungal Life Cycle
 Majority of the species are multi-celled
 Reproduce asexually quite often, but given the opportunity they also
reproduce sexually
 Form lots of nonmotile spores
 Spores - reproductive cells that germinate after dispersal
 Spores give rise to a mesh of mycelium
 Mycelium – a mesh of branched filaments
 Mycelium rapidly grows over or into organic matter
 Hypha – each filament in a mycelium
 Cytoplasm of hypha cells interconnects so nutrients flow throughout the
mycelium
 Have septa – divide the filament into compartments containing a single
nucleus
 When filaments lack septa they are multinucleate or coenocytic
 Cell walls contain chitin
Basidiomycetes - Club Fungi
 25,000 or so species of club fungi
 spores are club shaped
 saprobic species are important decomposers
 Ex. mushrooms, shelf fungi, coral fungi, puffballs
 fungal rusts and smuts can destroy fields wheat, corn, etc
 Agaricus brunnescens – the common grocery store mushroom
 Amillaria bulbosa – one of the oldest and largest organisms
 One individual extends through 15 hectacres of soil and may weigh more
than 10,000 kg
 Has been growing for more than 1,500 years
Examples of a Fungal Life Cycle
 A. brunnescens – common mushroom
 Produces short lived reproductive bodies, mushrooms, that are its
aboveground parts
 Mycelium is buried in soil
 A mushroom has a stalk and cap
 Gills (fine tissue sheets) line the caps inner surface
 Basidiospores – are spores under cap
 When spores are dispersed and land on a suitable site, it germinates and
gives rise to haploid mycelium
 If 2 hyphae fuse they form dikaryotic mycelium and form an extensive
mycelium
 When conditions are favorable mushrooms form.
After nuclear fusion, the club
shaped structure (now 2n) will
produce and bear haploid spores
at the four tips of the cell
diploid (2n)
nuclear fusion
meiosis
haploid (n)
club-shaped structures
having two nuclei (n+n)
form at the margin of
each gill
spores (n)
spores released
each germinating spore
gives rise to a hypha
that grow and becomes
a branching mycelium
after cytoplasmic fusion,
a dikaryotic (n+n) mycelium
gives rise to spore-bearing
bodies (mushrooms)
Spores and More Spores
 Spores are usually small and dry
 Air currents disperse them
 Fungus produces sexual spores, asexual spores or both
 Which spores that are produced depends on contact with a suitable
hypha, food availability, and how cool or damp conditions are
 Each fungal class produces unique sexual spores
 Each spore that germinates can be the start of a hypha and mycelium
 Stalked reproductive structures may develop on many of the hyphae and
produce more asexual spores
 These can form more mycelium
Zygomycetes
 Parasitic species that feed on insects
 Most live in soil decaying plants or animal material and stored food
 A thick walled sexual spore (2n) zygote, forms when it reproduces sexually
 Zygosporangium – a thin clear covering encloses the zygote
 Zygote goes through meiosis and gives rise to a specialized hypha that bears
a spore sac
 Each spore can give rise to a mycelium
 Ex. Black bread mold
Ascomycetes – The Sac Fungi
 Sac fungi
 Most form sexual spores called ascospores within sac-shaped cells (asci)
 Resemble flasks, globes, and shallow cups
 Reproductive structures are in asci of multicelled species
 Ex. Truffles, morels, penicillium, aspergillus (multi-celled)
 Ex. Yeasts (single celled)
Exclusive Spores of the Imperfect Fungi
 Nobody knows what kind of sexual spores they produce, so they are not
classified
Fungal Symbionts
 Fungi was here as symbionists when plants first invaded the land
 Symbiosis – species that live together in close association
 Mutualism – benefits both partners or does one of them no harm
Lichens
 Intertwined with one or more photosynthetic species
 Fungal part is mycobiont
 Photosynthetic part is photobiont
 Typically colonize sites on sunbaked or frozen rocks, fence posts,
gravestones.
 Mutualistic associations between fungi and algae
 Algae is usually cyanobacteria
 Fungi provides water and protection from the environment
 Algae provides sugar from photosynthesis and nitrogen is provided if the
algae is nitrogen fixing
Mycorrhizae
 Mutualistic association between fungi and roots
 Fungus increases the ability of the roots to absorb minerals
As Fungi Go, So Go The Forests
 Number and kinds of fungi are declining at alarming rates
 Decline does correlate with rising air pollution
 When fungi die trees lose vital support system and they become vulnerable to
severe frost and drought
 Fungi help plants in another way because many of them are premier
decomposers. They break down the organic compounds in their
surroundings
 Fungi grow in or on organic matter and secrete enzymes that digest it into
pieces that individual cells can absorb
Chapter 24: Ode To The Fungus Among Us
Characteristics of Fungi
Mode of Nutrition
 Fungi are _______________
 Most are _______________
 Saprobes –
 Others are _______________
 Parasites –
 Without the fungi (and heterotrophic bacteria) organisms would slowly
become buried in their own waste and life could not go on.
 ____________ known fungal species and at least a million more unknown
species
 Fungi evolved before ________ million years ago
 Some moved onto land ________ million years ago
Major Groups



 The vast majority of species are _______________
 Other kinds of fungi known as “imperfect fungi” are lumped together, but not
in a formal taxonomic group.
Key Features of Fungal Life Cycle
 Majority of the species are multi-celled
 Reproduce ______________ quite often, but given the opportunity they also
reproduce ______________
 Form lots of _______________ spores
 Spores  Spores give rise to a mesh of mycelium
 Mycelium –
 Mycelium rapidly grows over or into organic matter
 Hypha –
 Cytoplasm of hypha cells interconnects so nutrients flow throughout the
mycelium
 Have septa –
 When filaments lack septa they are multinucleate or coenocytic

Consider the Club Fungi
 __________ or so species of club fungi
 Spores are club shaped
 Saprobic species are important decomposers
 Ex.
 Fungal rusts and __________ can destroy fields wheat, corn, etc
 Agaricus brunnescens –
 Amillaria bulbosa –
 One individual extends through 15 hectacres of soil and may weigh more
than 10,000 kg
 Has been growing for more than 1,500 years
Examples of a Fungal Life Cycle
 A. brunnescens –
 Produces short lived reproductive bodies, _______________, that are its
aboveground parts

 A mushroom has a _________ and __________
 Gills (fine tissue sheets) line the caps inner surface
 Basidiospores –
 When spores are dispersed and land on a suitable site, it germinates and
gives rise to haploid mycelium
 If ____ hyphae fuse they form dikaryotic mycelium and form an extensive
mycelium
 When conditions are favorable mushrooms form.
After nuclear fusion, the club
shaped structure (now 2n) will
produce and bear haploid spores
at the four tips of the cell
diploid (2n)
nuclear fusion
meiosis
haploid (n)
club-shaped structures
having two nuclei (n+n)
form at the margin of
each gill
spores (n)
spores released
each germinating spore
gives rise to a hypha
that grow and becomes
a branching mycelium
after cytoplasmic fusion,
a dikaryotic (n+n) mycelium
gives rise to spore-bearing
bodies (mushrooms)
Spores and More Spores
 Spores are usually small and dry

 Fungus produces sexual spores, asexual spores or both
 Which spores that are produced depends on contact with a suitable
____________, food availability, and how cool or damp conditions are
 Each fungal class produces unique ____________ spores

 Stalked reproductive structures may develop on many of the hyphae and
produce more asexual spores

Producers of Zygosporangia

 Most live in soil decaying plants or animal material and stored food
 A thick walled sexual spore (2n) zygote, forms when it reproduces sexually
 Zygosporangium –
 Zygote goes through ____________ and gives rise to a specialized hypha
that bears a spore sac
 Each spore can give rise to a mycelium
 Ex.
Producers of Ascospores

 Most form sexual spores called ascospores within sac-shaped cells (asci)

 Reproductive structures are in asci of multicelled species
 Ex.
 Ex.
Exclusive Spores of the Imperfect Fungi
 Nobody knows what kind of sexual spores they produce, so they are not
classified
The Symbionts Revisited
 Fungi was here as symbionists when plants first invaded the land
 Symbiosis – species that live together in close association
 Mutualism – benefits both partners or does one of them no harm
Lichens
 Intertwined with one or more photosynthetic species
 Fungal part is _______________
 Photosynthetic part is _______________
 Typically colonize sites on sunbaked or frozen rocks, fence posts,
gravestones.
 Mutualistic associations between __________ and __________
 Algae is usually __________________
 Fungi provides __________ and protection from the environment
 Algae provides __________ from photosynthesis and nitrogen is provided if
the algae is nitrogen fixing
Mycorrhizae
 Mutualistic association between __________ and __________
 Fungus increases the ability of the roots to absorb minerals
As Fungi Go, So Go The Forests
 Number and kinds of fungi are declining at alarming rates
 Decline does correlate with rising ______ _______________
 When fungi die trees lose vital support system and they become vulnerable to
severe frost and drought
 Fungi help plants in another way because many of them are premier
decomposers. They break down the organic compounds in their
surroundings
 Fungi grow in or on ___________ matter and secrete ____________ that
digest it into pieces that individual cells can absorb