FUNGI
Chapter 21
The Kingdom Fungi
Section 1
What are Fungi?

Fungi are eukaryotic heterotrophs that have cell
walls
 The
cell wall is made of chitin, the same material that
makes up the external skeletons of insects



Fungi digest their food outside of their bodies and
then absorb it
Many feed by absorbing nutrients from decaying
matter
Others live as parasites
Structure and Function of Fungi


Yeasts – unicellular
All other fungi – multicellular
 Composed
 Some
of thin filaments called hyphae
hyphae have cross walls, others do not
Fungus Structure


Mycelium – many hyphae tangled together into a
thick mass
Fruiting Body – reproductive structure
Reproduction in Fungi

Most fungi reproduce sexually and asexually
Reproduction in Fungi
Asexual Reproduction


Hyphae break off and
begin to grow on their
own
Some fungi produce
spores, which scatter
and grow

Sporangia – structures
that produce spores
Sexual Reproduction


Sexual reproduction
involves two mating
types: “+” (plus) and “–”
(minus)
Hyphae of opposite
mating types meet and
fuse, bringing “+” and
“–” nuclei together in
one cell
How Fungi Spread



Many fungi produce dry spores that scatter easily in
the wind
If these spores are to germinate, they must land in
an environment with the proper combination of
temperature, moisture, and food so they can grow
Other fungi are specialized to lure animals, which
disperse spores over long distances
Classification of Fungi
Chapter 21
Classification of Fungi


Fungi are classified according to their structure and
method of reproduction.
The four main groups of fungi are:
 Common
molds (Zygomycota)
 Sac fungi (Ascomycota)
 Club fungi (Basidiomycota)
 Imperfect fungi (Deuteromycota)
Common Molds

Zygomycetes – familiar molds that grow on meat,
cheese, and bread
 Have
life cycles that include a zygospore (contains
zygotes formed during the sexual phase of the mold’s
life cycle)
Structure and Function of Bread Mold

Black bread mold (a zygomycete) has two types of
hyphae
 Rhizoids
- rootlike hyphae that penetrate the bread's
surface
 Stolons - stemlike hyphae that run along the surface of
the bread

Reproduce both sexually and asexually
Life Cycle of Black Bread Mold
FERTILIZATION
MEIOSIS
Asexual
Reproduction
Sexual
Reproduction
The Sac Fungi

Members of the phylum Ascomycota
 More


than 30,000 species
Names for the ascus – a reproductive structure that
contains spores
Life cycle includes both sexual and asexual
reproduction
Life Cycle of Sac Fungi
Sexual Reproduction
Asexual Reproduction
Yeasts


Unicellular fungi
Yeasts reproduce sexually and asexually
 Budding
– the process of asexual reproduction in
yeasts

Dry granules of yeast contain ascospores, which
become active in a moist environment
The Club Fungi


The phylum Basidiomycota, or club fungi, gets its
name from a specialized reproductive structure that
resembles a club
The spore bearing structure is called the basidium
 Found

in the gills on the underside of mushroom caps
Has a complicated life cycle
Life Cycle of Club Fungi
The Diversity of Club Fungi
The Imperfect Fungi



Phylum Deuteromycota
Cannot be placed in other phyla because
researchers have never been able to observe a
sexual phase in their life cycles
The species Penicillium notatum is a mold that
frequently grows on fruit
 Source
of the antibiotic penicillin
Ecology of Fungi
Section 3
All Fungi are Heterotrophs




Rely on other organisms for their energy
Many are saprobes – organisms that obtain food
from decaying matter
Some are parasites – harm other organisms while
living on or in them
Some are symbionts – live in mutually beneficial
association with other species
Fungi as Decomposers


Fungi play an essential role in maintaining
equilibrium in nearly every ecosystem
Fungi recycle nutrients by breaking down the bodies
and wastes of other organisms
Fungi as Parasites


Can cause serious plant and animal diseases
A few cause human diseases
Plant Diseases


Responsible for the loss of about 15% of crops
grown in temperate regions
Responsible for up to 50% of crop loss in tropical
areas
Human Diseases

Examples of fungus-caused disorders include:
 Athlete’s
foot
 Ringworm
 Thrush
Other Animal Diseases

Deadly grasshopper infection by one fungus called
Cordyceps
Symbiotic Relationships


Some fungi form symbiotic relationships in which
both partners benefit
Examples:
 Lichens
 Mycorrhizae
Lichens



Symbiotic association between a fungus and a
photosynthetic organism (either green algae or
cyanobacteria)
The algae or cyanobacteria carry out
photosynthesis, providing the fungus with a source
of energy
The fungus provides the algae or bacteria with
water and minerals and protects the green cells
from intense sunlight
Structure of Lichens
Lichens
Mycorrhizae


Association of plant roots and fungi
Researchers estimate that 80% of all plant species
form mycorrhizae with fungi