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 fusionmeiosis
haploid (n)
club-shaped structures
having two nuclei (n+n) spores (n)
form at the margin of
each gill
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 fusionmeiosis
haploid (n)
club-shaped structures
having two nuclei (n+n) spores (n)
form at the margin of
each gill
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