by Dana Krempels
Introduction
Kingdom
Fungi is an ostensibly monophyletic assemblage of ecologically important
organisms that not only perform the vital function of decomposition, but
also engage in a wide variety of symbiotic relationships with other species.Although
once thought to be related to plants, fungi are now known to share a more
recent common ancestor with animals than with plants.Several
characteristics set fungi apart from all other organisms, as you have learned
in lecture.
In
today's workshop, your goals will be to
1.Understand
the general terminology associated with fungi, their structure and function.
2.Understand
the general life cycle of the fungi, and how this life cycle is similar
and different
in
each of the major fungal taxa.
3.Consider
the important ecological roles various fungi play as decomposers and as
symbionts
in a wide array of symbiotic relationships.
I.Structure
and Function of Fungi:Terminology
Discuss
the precise meanings of the following terms as they relate to fungi.
A.Anatomy
1.mycelium
-
2.thallus
-
3.hypha
(pl. hyphae) -
4.haustoria
-
5.coenocytic
-
6.septum
(pl. septa) -
7.chitin
-
8.mold
-
9.yeast
-
10.saprobe
-
B.Life
Cycle
1.sporangium
-
2.conidium
(pl. conidia) -
3."+"
and "-" mating types -
3.plasmogamy
-
4.karyogamy
-
5.dikaryotic
-
6.fruiting
body -
C.Taxonomy
1.CHYTRIDIOMYCOTA
a.What
characteristics to the Chytridiomycota share with more derived fungi?
b.What
characteristics do Chytrids exhibit that are NOT FOUND in other fungi?
c.Besides
the other fungi, with what other major group are the chytrids believed
to share an
evolutionary
affinity?
2.ZYGOMYCOTA
a.What
is the common name of Phylum Zygomycota?Can
you think of a familiar example?
b.In
the Zygomycota, describe each of the following, and list its ploidy
(haploid, diploid
or
dikaryotic):
i.mycelium:
ii.zygosporangium:
iii.zygospore:
3.ASCOMYCOTA
a.What
is the common name of Phylum Ascomycota?Can
you think of a familiar example?
b.In
the Ascomycota, describe each of the following, and list its ploidy
(haploid, diploid
or
dikaryotic):
i.mycelium:
ii.ascocarp:
iii.ascus:
iv.ascospore:
4.BASIDIOMYCOTA
a.What
is the common name of Phylum Basidiomycota?Can
you think of a familiar
example?
b.In
the Basidiomycota, describe each of the following, and list its ploidy
(haploid, diploid
or
dikaryotic):
i.mycelium:
ii.basidiocarp:
iii.basidium:
iv.basidiospore:
II.Fungal
Life Cycles
The
diagram below shows a generalized fungus life cycle.Study
this overview, and note the ploidy of each life cycle stage.Next,
use the three template life cycle on the following pages to fill in the
names and ploidies of every similar life cycle stage in the (1) Zygomycota,
(2) Ascomycota and (3) Basidiomycota.
1.Is
the life cycle diagrammed above sexual or asexual?How
can you tell?
2.If
the generalized fungus above were to engage in asexual reproduction, where
on the life cycle
diagram
would this occur?Draw it into the
diagram, indicating the ploidy of all relevant
structures.
3.Which
of the major fungal taxa do reproduce via asexual spores?Which
do not?
Below
is a diagram similar to the one on the previous page, but with three major
life cycle stages replaced by "A", "B" and "C".
4.In
the Zygomycota:
What
is the name of A?-
What
is its ploidy? -
What
is the name of B?-
What
is its ploidy? -
What
is the name of C?-
What
is its ploidy? -
What
are the resulting spores called?
What
is their ploidy?
5.In
the Ascomycota:
What
is the name of A?-
What
is its ploidy? -
What
is the name of B?-
What
is its ploidy? -
What
is the name of C?-
What
is its ploidy? -
What
are the resulting spores called?
What
is their ploidy?
6.In
the Basidiomycota:
What
is the name of A?-
What
is its ploidy? -
What
is the name of B?-
What
is its ploidy? -
What
is the name of C?-
What
is its ploidy? -
What
are the resulting spores called?
What
is their ploidy?
7.What
do you think is the evolutionary significance of the similarity of life
cycles across the three
fungal
taxa?
III.Fungi
in Symbiotic Relationships
Symbiosis
(literally "living together") occurs when two species maintain a close
ecological association.There are
many different types of symbiosis, each defined by the effect of the relationship
on each of the participating populations.Using
standard symbiosis shorthand, we will assign a population a "+" if it benefits
from a particular relationship, a "-" if it is harmed by the relationship,
and a "0" if it is not affected by the relationship.In
so doing, we can construct a grid of possible symbiotic relationships,
as shown below.
Discuss
each type of symbiosis, and then try to name a fungal association that
fits into that category.Be sure
to note whether the fungal symbiont is population A or population B, and
whether it is parasite, host, pathogen, prey item, predator, or other appropriate
term.There may be more than one
fungal association in any given category, and there may be none in some
of the categories.It's up to you
to recall them!
|
type
of interaction
|
pop'n
A
|
pop'n
B
|
nature
of effect
|
|
mutualism
|
|
|
obligatory;
both populations benefit
|
|
EXAMPLES:
|
|
|
|
|
protocooperation
|
|
|
NOT
obligatory; both pop'ns benefit
|
|
EXAMPLES:
|
|
|
|
|
competition
|
|
|
populations
inhibit one another
|
|
EXAMPLES:
|
|
|
|
|
neutralism
|
|
|
populations
don't affect one another
|
|
EXAMPLES:
|
|
|
|
|
predation
|
|
|
predator
(A) kills & consumes prey (B)
|
|
EXAMPLES:
|
|
|
|
|
parasitism
|
|
|
parasite
(A) exploits the host (B), but
does
not kill it outright |
|
EXAMPLES:
|
|
|
|
|
parasitoidism
|
|
|
parasitoid
(A) eventually kills host (B)
|
|
EXAMPLES:
|
|
|
|
|
commensalism
|
|
|
commensal
(A) benefits; host (B) not
affected |
|
EXAMPLES:
|
|
|
|
|
amensalism
|
|
|
A
inhibited; B unaffected
|
|
EXAMPLES:
|
|
|
|
IV.Discussion
Questions
1.In
what ways might a broad-spectrum fungicide (i.e., one that kills all fungi)
applied to an
agricultural
plant crop be harmful to the crop?
2.Humans
have been able to obtain many different medicines (such as antibiotics)
from fungi.Of
what
possible use to the fungi are these compounds?
3.Just
about everyone knows that certain species of mushrooms can be hallucinogenic.Of
what
possible
utility to the fungus is such a property?
4.The
American Chestnut Tree, which once made up more than 25% of North American
hardwood forests, were killed off by a deadly fungal blight that does not
affect the closely related Asian Chestnut Tree.It
is believed that the fungus was accidentally imported with Asian Chestnut
trees imported as ornamentals.Why
do you suppose the fungus affects only the North American trees?What
does this tell you about the importance of careful control of imported
species?Do you think that such accidental
importation of pathogens (of plants, animals, etc.) will become more frequent
or more rare in the future?Why?
5.If
fungi were to suffer a massive, global, multi-species extinction, what
do you think the effect on various ecosystems would be?Explain
in some detail, using specific examples.